LTC2497 - 16-Bit 8-/16-Channel Delta Sigma ADC with Easy Drive Input Current Cancellation and I2C Interface

Features

  • Up to Eight Differential or 16 Single-Ended Inputs
  • Easy Drive™ Technology Enables Rail-to-Rail Inputs with Zero Differential Input Current
  • Directly Digitizes High Impedance Sensors with Full Accuracy
  • 2-Wire I2C Interface with 27 Addresses Plus One Global Address for Synchronization
  • 600nVRMS Noise (0.02LSB Transition Noise)
  • GND to VCC Input/Reference Common Mode Range
  • Simultaneous 50Hz/60Hz Rejection
  • 2ppm INL, No Missing Codes
  • 1ppm Offset and 15ppm Full-Scale Error
  • No Latency: Digital Filter Settles in a Single Cycle, Even After a New Channel Is Selected
  • Single Supply, 2.7V to 5.5V Operation (0.8mW)
  • Internal Oscillator
  • Tiny 5mm × 7mm QFN Package
Designed for Automotive and Transportation Applications
AEC-Q100 generic family data available for specific packages


Typical Application

LTC2497 Typical Application
LTC2497 Typical Application

Description

The LTC2497 is a 16-channel (eight differential), 16-bit, No Latency ΔΣ ADC with Easy Drive technology and a 2-wire, I2C interface. The patented sampling scheme eliminates dynamic input current errors and the shortcomings of on-chip buffering through automatic cancellation of differential input current. This allows large external source impedances and rail-to-rail input signals to be directly digitized while maintaining exceptional DC accuracy.

The LTC2497 includes an integrated oscillator. This device can be configured to measure an external signal from combinations of 16 analog input channels operating in single-ended or differential modes. It automatically rejects line frequencies of 50Hz and 60Hz simultaneously.

The LTC2497 allows a wide, common mode input range (0V to VCC), independent of the reference voltage. Any combination of single-ended or differential inputs can be selected and the first conversion, after a new channel is selected, is valid. Access to the multiplexer output enables optional external amplifiers to be shared between all analog inputs and auto calibration continuously removes their associated offset and drift.

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing
RoHS
LTC2497CUHF#PBF 5x7 QFN-38 UHF C 05-08-1701 Yes
LTC2497CUHF#TRPBF 5x7 QFN-38 UHF C 05-08-1701 Yes
LTC2497IUHF#PBF 5x7 QFN-38 UHF I 05-08-1701 Yes
LTC2497IUHF#TRPBF 5x7 QFN-38 UHF I 05-08-1701 Yes


LTC2497 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC2497CUHF#PBF 5x7 QFN-38 C $3.88 $2.65 Yes
LTC2497CUHF#TRPBF 5x7 QFN-38 C $3.94 $2.71 Yes
LTC2497IUHF#PBF 5x7 QFN-38 I $4.66 $3.18 Yes
LTC2497IUHF#TRPBF 5x7 QFN-38 I $4.72 $3.24 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1012A-B LTC2497 Demo Board | 16-bit, 8-ch I2C Easy Drive ADC (req DC2026) $50.00
Buy Now

Companion Boards

Part Number Description Price Documentation
DC2026C Linduino One Isolated USB Demo Board: An Arduino- and QuikEval-Compatible Code Development Platform $75.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

Please contact your local sales representative for more information regarding reliability reports and AEC-Q100 data or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC2497IUHF#PBF 5x7 QFN-38 I $4.66 $3.18 Yes
LTC2497IUHF#TRPBF 5x7 QFN-38 I $4.72 $3.24 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Applications

  • Direct Sensor Digitizer
  • Direct Temperature Measurement
  • Instrumentation
  • Industrial Process Control

Product Notifications

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Design Tools

Linduino

Linduino is an Arduino compatible platform for developing and distributing firmware libraries and code for SPI and I²C-compatible integrated circuits. The Linduino One board interfaces to more than 300 QuikEval demonstration cards, supporting a variety of product types including analog-to-digital converters (ADCs)digital-to-analog converters (DACs)power monitors, and more. Firmware libraries for individual devices are written in C and designed to be portable to a wide variety of processors and microcontrollers. Each library has a demonstration program that can be uploaded to the Linduino One platform to allow the circuit and software to be quickly and easily verified.

Click here for more information on Linduino

Code

Linduino is Linear Technology's Arduino compatible system for developing and distributing firmware libraries and example code for Linear Technology’s integrated circuits. The code below can be downloaded or copied and pasted into your project. Please visit the Linduino Home Page for demo board, manual and setup information.

This part is Code Supported: There is example code available for this part. The code below may rely on other drivers available in the full library.

Download LTC2497 - DC1012AB Linduino.INO File

/*!
Linear Technology DC1012A-B Demonstration Board.
LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator. Equipment
   required is a precision voltage source and a precision voltmeter. Additionally,
   an external power supply is required to provide a negative voltage for Amp V-. 
   Set it to anywhere from -1V to -5V. Set Amp V+ to Vcc. Ensure the COM and REF-
   pins are connected to ground. The REF+ pin should be connected to +5V.

  How to test Single-Ended mode:
   The voltage source should be connected to the ADC such that the negative lead is
   connected to the COM(common) pin. The positive lead may be connected to any
   channel input. Ensure voltage is within analog input voltage range -0.3 to 2.5V.

  How to test Differential Mode:
   The voltage source should be connected with positive and negative leads to paired
   channels. The voltage source negative output must also be connected to the COM
   pin in order to provide a ground-referenced voltage. Ensure voltage is within 
   analog input voltage range -0.3V to +2.5V. Swapping input voltages results in a
   reversed polarity reading.


USER INPUT DATA FORMAT:
 decimal : 1024
 hex     : 0x400
 octal   : 02000  (leading 0 "zero")
 binary  : B10000000000
 float   : 1024.0

@endverbatim

http://www.linear.com/product/LTC2497

http://www.linear.com/product/LTC2497#demoboards

REVISION HISTORY
$Revision: 2266 $
$Date: 2014-03-17 13:39:33 -0700 (Mon, 17 Mar 2014) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.

 */

/*! @file
    @ingroup LTC2497
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include <SPI.h>
#include "UserInterface.h"
#include "LT_I2C.h"
#include "QuikEval_EEPROM.h"
#include "LTC24XX_general.h"
#include "LTC2497.h"

// Function Declaration
void print_title();                             // Print the title block
void print_prompt();                            // Prompt the user for an input command
void print_user_command(uint8_t menu);          // Display selected differential channels

int8_t menu_1_read_single_ended();
int8_t menu_2_read_differential();
void menu_3_set_address();

// Global variables
static uint8_t demo_board_connected;                //!< Set to 1 if the board is connected
static float LTC2497_vref = 5.0;                    //!< The ideal reference voltage
static uint8_t i2c_address = LTC2497_I2C_ADDRESS;   //!< I2C address in 7 bit format for part
static uint16_t timeout = 300;                      //!< 300 ms timeout      

// Constants

//! Lookup table to build the command for single-ended mode
const uint8_t BUILD_COMMAND_SINGLE_ENDED[16] = {LTC24XX_MULTI_CH_CH0, LTC24XX_MULTI_CH_CH1, LTC24XX_MULTI_CH_CH2, LTC24XX_MULTI_CH_CH3,
    LTC24XX_MULTI_CH_CH4, LTC24XX_MULTI_CH_CH5, LTC24XX_MULTI_CH_CH6, LTC24XX_MULTI_CH_CH7,
    LTC24XX_MULTI_CH_CH8, LTC24XX_MULTI_CH_CH9, LTC24XX_MULTI_CH_CH10, LTC24XX_MULTI_CH_CH11,
    LTC24XX_MULTI_CH_CH12, LTC24XX_MULTI_CH_CH13, LTC24XX_MULTI_CH_CH14, LTC24XX_MULTI_CH_CH15
                                                };    //!< Builds the command for single-ended mode

//! Lookup table to build the command for differential mode
const uint8_t BUILD_COMMAND_DIFF[16] = {LTC24XX_MULTI_CH_P0_N1, LTC24XX_MULTI_CH_P2_N3, LTC24XX_MULTI_CH_P4_N5, LTC24XX_MULTI_CH_P6_N7,
                                        LTC24XX_MULTI_CH_P8_N9, LTC24XX_MULTI_CH_P10_N11, LTC24XX_MULTI_CH_P12_N13, LTC24XX_MULTI_CH_P14_N15,
                                        LTC24XX_MULTI_CH_P1_N0, LTC24XX_MULTI_CH_P3_N2, LTC24XX_MULTI_CH_P5_N4, LTC24XX_MULTI_CH_P7_N6,
                                        LTC24XX_MULTI_CH_P9_N8, LTC24XX_MULTI_CH_P11_N10, LTC24XX_MULTI_CH_P13_N12, LTC24XX_MULTI_CH_P15_N14
                                        };      //!< Build the command for differential mode

//! Initialize Linduino
void setup()
{
  char demo_name[]="DC1012";    // Demo Board Name stored in QuikEval EEPROM
  quikeval_I2C_init();          // Configure the EEPROM I2C port for 100kHz
  quikeval_I2C_connect();       // Connect I2C to main data port
  Serial.begin(115200);         // Initialize the serial port to the PC
  print_title();
  
  demo_board_connected = discover_demo_board(demo_name);
  if (demo_board_connected)
  {
    print_prompt();
  }
  else{
    Serial.println(F("EEPROM not detected, will attempt to proceed"));
    demo_board_connected = 1;
    print_prompt();
  }
}

//! Repeats Linduino loop
void loop()
{
  int16_t user_command;                 // The user input command
  uint8_t acknowledge = 0;
  if (demo_board_connected)
  {
    if (Serial.available())             // Check for user input
    {
      user_command = read_int();        // Read the user command
      if (user_command != 'm')
        Serial.println(user_command);   // Prints the user command to com port
      Serial.flush();
      switch (user_command)
      {
        case 1:
          acknowledge |= menu_1_read_single_ended();
          break;
        case 2:
          acknowledge |= menu_2_read_differential();
          break;
        case 3:
          menu_3_set_address();
          break;
        default:
          Serial.println(F("Incorrect Option"));
      }
      if(acknowledge)
        Serial.println(F("***** I2C ERROR *****"));
      Serial.print(F("\n*************************\n"));
      print_prompt();
    }
  }
}

// Function Definitions

//! Prints the title block when program first starts.
void print_title()
{
  Serial.print(F("\n*****************************************************************\n"));
  Serial.print(F("* DC1012A-B Demonstration Program                               *\n"));
  Serial.print(F("*                                                               *\n"));
  Serial.print(F("* This program demonstrates how to send data and receive data   *\n"));
  Serial.print(F("* from the 16-bit ADC.                                          *\n"));
  Serial.print(F("*                                                               *\n"));
  Serial.print(F("*                                                               *\n"));
  Serial.print(F("* Set the baud rate to 115200 and select the newline terminator.*\n"));
  Serial.print(F("*                                                               *\n"));
  Serial.print(F("*****************************************************************\n"));
}

//! Prints main menu.
void print_prompt()
{
  Serial.print(F("\n1-Read Single-Ended\n"));
  Serial.print(F("2-Read Differential\n"));
  Serial.print(F("3-Set I2C Address\n"));
  Serial.print(F("Enter a Command: "));
}

//! Display selected differential channels. Displaying single-ended channels is
//! straightforward; not so with differential because the inputs can take either polarity.
void print_user_command(uint8_t menu)
{
  switch (menu)
  {
    case 0:
      Serial.print(F("0P-1N"));
      break;
    case 1:
      Serial.print(F("2P-3N"));
      break;
    case 2:
      Serial.print(F("4P-5N"));
      break;
    case 3:
      Serial.print(F("6P-7N"));
      break;
    case 4:
      Serial.print(F("8P-9N"));
      break;
    case 5:
      Serial.print(F("10P-11N"));
      break;
    case 6:
      Serial.print(F("12P-13N"));
      break;
    case 7:
      Serial.print(F("14P-15N"));
      break;
    case 8:
      Serial.print(F("1P-0N"));
      break;
    case 9:
      Serial.print(F("3P-2N"));
      break;
    case 10:
      Serial.print(F("5P-4N"));
      break;
    case 11:
      Serial.print(F("7P-6N"));
      break;
    case 12:
      Serial.print(F("9P-8N"));
      break;
    case 13:
      Serial.print(F("11P-10N"));
      break;
    case 14:
      Serial.print(F("13P-12N"));
      break;
    case 15:
      Serial.print(F("15P-14N"));
      break;
  }
  Serial.print(F(": "));
}

//! Read channels in single-ended mode
//! @return 0 if successful, 1 is failure
int8_t menu_1_read_single_ended()
{
  uint8_t adc_command;     // The LTC2497 command word
  int16_t user_command;    // The user input command
  int32_t adc_code = 0;    // The LTC2497 code
  float adc_voltage=0;     // The LTC2497 voltage
  
  while (1)
  {
    uint8_t ack = 0;
    
    Serial.print(F("*************************\n\n"));
    Serial.print(F("0-CH0  8-CH8\n"));
    Serial.print(F("1-CH1  9-CH9\n"));
    Serial.print(F("2-CH2  10-CH10\n"));
    Serial.print(F("3-CH3  11-CH11\n"));
    Serial.print(F("4-CH4  12-CH12\n"));
    Serial.print(F("5-CH5  13-CH13\n"));
    Serial.print(F("6-CH6  14-CH14\n"));
    Serial.print(F("7-CH7  15-CH15\n"));
    Serial.print(F("16-ALL\n"));
    Serial.print(F("m-Main Menu\n"));
    Serial.print(F("Enter a Command: "));

    user_command = read_int();                                      // Read the single command
    if (user_command == 'm')
      return(0);
    Serial.println(user_command);
    
    if (user_command == 16)
    {
      Serial.print(F("ALL\n"));
      adc_command = BUILD_COMMAND_SINGLE_ENDED[0];                  // Build ADC command for channel 0     
      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);    // Throws out last reading
      
      for (int8_t x = 0; x <= 15; x++)                              // Read all channels in single-ended mode
      {
        delay(170);

        adc_command = BUILD_COMMAND_SINGLE_ENDED[(x + 1) % 16];

        ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);
        adc_voltage = LTC2497_code_to_voltage(adc_code, LTC2497_vref);
        if(!ack)
        {
          Serial.print(F("  ****"));
          Serial.print(F("CH"));
          Serial.print(x);
          Serial.print(F(": "));
          Serial.print(adc_voltage, 4);
          Serial.print(F("V\n\n"));
        }
        else
        {
          Serial.print(F("  ****"));
          Serial.print(F("CH"));
          Serial.print(x);
          Serial.print(F(": "));
          Serial.print(F("Error in read"));
          return 1; 
        }
      }
    }
    else
    {
      adc_command = BUILD_COMMAND_SINGLE_ENDED[user_command];
      Serial.print(F("ADC Command: 0x"));
      Serial.println(adc_command, HEX);
      Serial.print(F("I2C address is: "));
      Serial.println(i2c_address,HEX);
    
      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);     // Throws out last reading
      
      
      delay(170);

      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);     // Now we're ready to read the desired data
      if(!ack){
          Serial.print(F("Received Code: 0x"));
          Serial.println(adc_code, HEX);
          adc_voltage = LTC2497_code_to_voltage(adc_code, LTC2497_vref);
          Serial.print(F("  ****"));
          Serial.print(F("CH"));
          Serial.print(user_command);
          Serial.print(F(": "));
          Serial.print(adc_voltage, 4);
          Serial.print(F("V\n\n"));
      }
      else 
      {
        Serial.println(F("Device NAK'd, please check address and try again"));
        return 1; 
      }
    }
  }
  return(0);
}

//! Read channels in differential mode
//! @return 0 if successful, 1 is failure
int8_t menu_2_read_differential()
{
  int8_t y;                 // Offset into differential channel array to select polarity
  uint8_t adc_command;      // The LTC2497 command word
  int16_t user_command;     // The user input command
  int32_t adc_code = 0;     // The LTC2497 code
  float adc_voltage;        // The LTC2497 voltage

  while (1)
  {
    uint8_t ack = 0;
    
    Serial.print(F("\n*************************\n\n")); // Display  differential menu
    Serial.print(F("0-0P-1N     8-1P-0N\n"));
    Serial.print(F("1-2P-3N     9-3P-2N\n"));
    Serial.print(F("2-4P-5N     10-5P-4N\n"));
    Serial.print(F("3-6P-7N     11-7P-6N\n"));
    Serial.print(F("4-8P-9N     12-9P-8N\n"));
    Serial.print(F("5-10P-11N   13-11P-10N\n"));
    Serial.print(F("6-12P_13N   14-13P-12N\n"));
    Serial.print(F("7-14P-15N   15-15P-14N\n"));
    Serial.print(F("16-ALL Even_P-Odd_N\n"));
    Serial.print(F("17-ALL Odd_P-Even_N\n"));
    Serial.print(F("m-Main Menu\n"));

    user_command = read_int();                        // Read the single command
    if (user_command == 'm')
      return(0);
    Serial.println(user_command);

    if ((user_command == 16) || (user_command == 17))
    {
      if (user_command == 16)
      {
        Serial.print(F("ALL Even_P-Odd_N\n"));        // Cycles through options 0-7
        y = 0;
      }
      if (user_command == 17)
      {
        Serial.print(F("ALL Odd_P-Even_N\n"));        // Cycles through options 8-15
        y = 8;
      }

      adc_command = BUILD_COMMAND_DIFF[y];            // Build the channel 0 and 1 for differential mode
      
      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);    // Throws out reading
      for (int8_t x = 0; x < 8; x++)                  // Read all channels in differential mode. All even channels are positive and odd channels are negative
      {
        delay(170);

        adc_command = BUILD_COMMAND_DIFF[((x + 1) % 8) + y];

        ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);
        if(!ack)
        {
          Serial.print(F("Received Code: 0x"));
          Serial.println(adc_code, HEX);
          adc_voltage = LTC2497_code_to_voltage(adc_code, LTC2497_vref);
          Serial.print(F("\n  ****"));
          print_user_command(x + y);
          Serial.print(F(": "));
          Serial.print(adc_voltage, 4);
          Serial.print(F("V\n"));
        }
        else 
        {
          Serial.println(F("Device NAK'd, please check I2C address"));
          return 1; 
        }
      }
    }
    else
    {
      // Reads and displays a selected channel
      adc_command = BUILD_COMMAND_DIFF[user_command];
      Serial.print(F("ADC Command: 0x"));
      Serial.println(adc_command, HEX);
      
      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);     // Throws out last reading
      delay(170);

      ack |= LTC2497_read(i2c_address, adc_command, &adc_code, timeout);
      if(!ack)
      {
        Serial.print(F("Received Code: 0x"));
        Serial.println(adc_code, HEX);
        adc_voltage = LTC2497_code_to_voltage(adc_code, LTC2497_vref);
        Serial.print(F("\n  ****"));
        print_user_command(user_command);
        Serial.print(adc_voltage, 4);
        Serial.print(F("V\n"));
      }
      else 
      {
        Serial.println(F("Device NAK'd, please check I2C address"));
        return 1;
      }
    }
  }
  return(0);
}

//! Set the I2C 7 bit address 
void menu_3_set_address()
{
    int16_t user_command;
    Serial.print(F("What is the I2C address of the part?\n"));
    Serial.print(F("Please enter in 7-bit format, decimal\n"));
    
    user_command =read_int();
    Serial.println(user_command);
    i2c_address = user_command&0x7F;
}

Download LTC2497 - Linduino Header File

/*!
LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation.

@verbatim

The LTC2497 is a 16-channel (eight differential), 16-bit, No Latency Delta
Sigma TM ADC with Easy Drive technology and a 2-wire, I2C interface. The 
patented sampling scheme eliminates dynamic input current errors and the 
shortcomings of on-chip buffering through automatic cancellation of
differential input current. This allows large external source impedances 
and rail-to-rail input signals to be directly digitized while maintaining
exceptional DC accuracy.

I2C DATA FORMAT (MSB FIRST):

Data In:
Byte #1                                     Byte #2

START  SA6 SA5 SA4 SA3 SA2 SA1 SA0 W SACK   1  0  EN SGL ODD A2 A1 A0 NACK  Stop 

Data Out:
Byte #1                                     Byte #2
                                            MSB 
Start   SA6 SA5 SA4 SA3 SA2 SA1 SA0 R SACK  SGN D15 D14 D13 D12 D11 D10 D9 MACK 

Byte #3                        Byte #4
                               LSB
D8 D7 D6 D5 D4 D3 D2 D1 MACK   D0 X X X X X X X MNACK   STOP

START       : I2C Start
Repeat Start: I2c Repeat Start
STOP        : I2C Stop 
SAx         : I2C Address
SACK        : I2C Slave Generated Acknowledge (Active Low)
MACK        : I2C Master Generated Acknowledge (Active Low)
MNACK       : I2c Master Generated Not Acknowledge
W           : I2C Write (0)
R           : I2C Read  (1)
Cx          : Command Code
Dx          : Data Bits
X           : Don't care
EN          : Enable Bit
SGL         : Single Ended Bit
ODD         : Polarity Bit
SGN         : Sign Bit


Example Code:
Read differential with CH0 as positive and CH1 as negative: 

    uint8_t ack;
    int32_t adc_code = 0;
    float adc_voltage;
    adc_command = LTC24XX_MULTI_CH_P0_N1;
    ack |= LTC2497_read(i2c_address, adc_command, &adc_code); 
    adc_voltage = LTC2497_code_to_voltage(adc_code, LTC2497_vref);
      
@endverbatim

http://www.linear.com/product/LTC2497

http://www.linear.com/product/LTC2497#demoboards

REVISION HISTORY
$Revision: 2266 $
$Date: 2014-03-17 13:39:33 -0700 (Mon, 17 Mar 2014) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

/*! @file
    @ingroup LTC2497
    Header for LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation
*/

#ifndef LTC2497_H
#define LTC2497_H

/*! @name I2C_Addresses
@{ */

//! I2C address of the LTC2497.
//! Configured by tying the ADR0, ADR1, and ADR2 pins high or low. See Table 1 of datasheet.
//! Uncomment LTC2497_I2C_ADDRESS to match demo board configuration.
//  Address assignment
// LTC2497 I2C Address                 //  AD2       AD1       AD0
// #define LTC2497_I2C_ADDRESS 0x14    //  Low       Low       Low
// #define LTC2497_I2C_ADDRESS 0x16    //  Low       Low       High
// #define LTC2497_I2C_ADDRESS 0x15    //  Low       Low       Float
// #define LTC2497_I2C_ADDRESS 0x26    //  Low       High      Low
// #define LTC2497_I2C_ADDRESS 0x34    //  Low       High      High
// #define LTC2497_I2C_ADDRESS 0x27    //  Low       High      Float
// #define LTC2497_I2C_ADDRESS 0x17    //  Low       Float     Low
// #define LTC2497_I2C_ADDRESS 0x25    //  Low       Float     High
// #define LTC2497_I2C_ADDRESS 0x24    //  Low       Float     Float
// #define LTC2497_I2C_ADDRESS 0x56    //  High      Low       Low
// #define LTC2497_I2C_ADDRESS 0x64    //  High      Low       High
// #define LTC2497_I2C_ADDRESS 0x57    //  High      Low       Float
// #define LTC2497_I2C_ADDRESS 0x74    //  High      High      Low
#define LTC2497_I2C_ADDRESS 0x76    //  High      High      High
// #define LTC2497_I2C_ADDRESS 0x75    //  High      High      Float
// #define LTC2497_I2C_ADDRESS 0x65    //  High      Float     Low
// #define LTC2497_I2C_ADDRESS 0x67    //  High      Float     High
// #define LTC2497_I2C_ADDRESS 0x66    //  High      Float     Float
// #define LTC2497_I2C_ADDRESS 0x35    //  Float     Low       Low
// #define LTC2497_I2C_ADDRESS 0x37    //  Float     Low       High
// #define LTC2497_I2C_ADDRESS 0x36    //  Float     Low       Float
// #define LTC2497_I2C_ADDRESS 0x47    //  Float     High      Low
// #define LTC2497_I2C_ADDRESS 0x55    //  Float     High      High
// #define LTC2497_I2C_ADDRESS 0x54    //  Float     High      Float
// #define LTC2497_I2C_ADDRESS 0x44    //  Float     Float     Low
// #define LTC2497_I2C_ADDRESS 0x46    //  Float     Float     High
// #define LTC2497_I2C_ADDRESS 0x45    //  Float     Float     Float

//! LTC2497 Global I2C Address.
#define LTC2497_I2C_GLOBAL_ADDRESS 0x77  //  Global Address
/*! @} */


//! Reads from LTC2497.
//! @return  1 if no acknowledge, 0 if acknowledge
uint8_t LTC2497_read(uint8_t i2c_address,   //!< I2C address (7-bit format) for part
                     uint8_t adc_command,   //!< Byte command written to LTC2497
                     int32_t *adc_code,     //!< 4 byte conversion code read from LTC2497
                     uint16_t timeout       //!< Timeout (in milliseconds)
                    );

//! Calculates the voltage corresponding to an ADC code, given the reference (in volts)
//! @return Returns voltage calculated from ADC code.
float LTC2497_code_to_voltage(int32_t adc_code,     //!< Code read from ADC
                              float vref            //!< VRef (in volts)
                             );

#endif  // LTC2497_H

Download LTC2497 - Linduino.CPP File

/*!
LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation.

@verbatim

The LTC2497 is a 16-channel (eight differential), 16-bit, No Latency Delta
Sigma TM ADC with Easy Drive technology and a 2-wire, I2C interface. The 
patented sampling scheme eliminates dynamic input current errors and the 
shortcomings of on-chip buffering through automatic cancellation of
differential input current. This allows large external source impedances 
and rail-to-rail input signals to be directly digitized while maintaining
exceptional DC accuracy.

@endverbatim

http://www.linear.com/product/LTC2497

http://www.linear.com/product/LTC2497#demoboards

REVISION HISTORY
$Revision: 2274 $
$Date: 2014-03-17 15:37:51 -0700 (Mon, 17 Mar 2014) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

//! @defgroup LTC2497 LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation

/*! @file
    @ingroup LTC2497
    Library for LTC2497: 16-Bit, 16-Channel Delta Sigma ADCs with Easy Drive Input Current Cancellation
*/

#include <stdint.h>
#include <Arduino.h>
#include "Linduino.h"
#include "LT_I2C.h"
#include "LTC2497.h"
#include "LTC24XX_general.h"

// Reads from LTC2497.
uint8_t LTC2497_read(uint8_t i2c_address, uint8_t adc_command, int32_t *adc_code, uint16_t timeout)
{
  return (LTC24XX_I2C_8bit_command_24bit_data(i2c_address, adc_command, adc_code, timeout));
}

// Calculates the voltage corresponding to an ADC code, given the reference (in volts)
float LTC2497_code_to_voltage(int32_t adc_code, float vref)
{
  return (LTC24XX_diff_code_to_voltage(adc_code, vref));
}

Download LTC24XX – Linduino Header File

/*!
LTC24XX General Library: Functions and defines for all SINC4 Delta Sigma ADCs.

@verbatim


LTC2442 / LTC2444 / LTC2445 / LTC2448 / LTC2449 (Are there don't care bits in the low channel counts?
SPI DATA FORMAT (MSB First):

            Byte #1                            Byte #2

Data Out :  !EOC DMY SIG D28 D27 D26 D25 D24   D23  D22  D21  D20  D19 D18 D17 D16
Data In  :  1    0   EN  SGL OS  S2  S1  S0    OSR3 OSR2 OSR1 OSR1 SPD X   X   X

            Byte #3                            Byte #4
            D15  D14 D13 D12 D11 D10 D9  D8    D7  D6  D5  D4 *D3  *D2 *D1 *D0
            X    X   X   X   X   X   X   X     X   X   X   X   X   X   X   X

!EOC : End of Conversion Bit (Active Low)
DMY  : Dummy Bit (Always 0)
SIG  : Sign Bit (1-data positive, 0-data negative)
Dx   : Data Bits
*Dx  : Data Bits Below lsb
EN   : Enable Bit (0-keep previous mode, 1-change mode)
SGL  : Enable Single-Ended Bit (0-differential, 1-single-ended)
OS   : ODD/Sign Bit
Sx   : Address Select Bit
0SRX : Over Sampling Rate Bits
SPD  : Double Output Rate Select Bit (0-Normal rate, auto-calibration on, 2x rate, auto_calibration off)

Command Byte #1
1    0    EN   SGL  OS   S2   S1   S0   Comments
1    0    0    X    X    X    X    X    Keep Previous Mode
1    0    1    0    X    X    X    X    Differential Mode
1    0    1    1    X    X    X    X    Single-Ended Mode

|  Coversion Rate    |  RMS  | ENOB | OSR  | Latency
Command Byte #2          |Internal | External | Noise |      |      |
|  9MHz   | 10.24MHz |       |      |      |
OSR3 OSR2 OSR1 OSR1 SPD  | Clock   |  Clock   |       |      |      |
0    0    0    0    0      Keep Previous Speed/Resolution
0    0    0    1    0      3.52kHz   4kHz       23uV    17     64     none
0    0    1    0    0      1.76kHz   2kHz       3.5uV   20.1   128    none
0    0    1    1    0      880Hz     1kHz       2uV     21.3   256    none
0    1    0    0    0      440Hz     500Hz      1.4uV   21.8   512    none
0    1    0    1    0      220Hz     250Hz      1uV     22.4   1024   none
0    1    1    0    0      110Hz     125Hz      750nV   22.9   2048   none
0    1    1    1    0      55Hz      62.5Hz     510nV   23.4   4096   none
1    0    0    0    0      27.5Hz    31.25Hz    375nV   24     8192   none
1    0    0    1    0      13.75Hz   15.625Hz   250nV   24.4   16384  none
1    1    1    1    0      6.87kHz   7.8125Hz   200nV   24.6   32768  none
0    0    0    0    1      Keep Previous Speed/Resolution
OSR3 OSR2 OSR1 OSR1 1      2X Mode  *all clock speeds double

Example Code:

Read Channel 0 in Single-Ended with OSR of 65536

    uint16_t miso_timeout = 1000;
    adc_command = LTC2449_CH0 | LTC2449_OSR_32768 | LTC2449_SPEED_2X;   // Build ADC command for channel 0
                                                                        // OSR = 32768*2 = 65536

    if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout))    // Check for EOC
        return;                                          // Exit if timeout is reached
    LTC2449_read(LTC2449_CS, adc_command, &adc_code);    // Throws out last reading
    
    if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout))    // Check for EOC
        return;                                          // Exit if timeout is reached
    LTC2449_read(LTC2449_CS, adc_command, &adc_code);    // Obtains the current reading and stores to adc_code variable

    // Convert adc_code to voltage
    adc_voltage = LTC2449_code_to_voltage(adc_code, LTC2449_lsb, LTC2449_offset_code);

@endverbatim

http://www.linear.com/product/LTC2449

http://www.linear.com/product/LTC2449#demoboards

REVISION HISTORY
$Revision: 1881 $
$Date: 2013-08-15 09:16:50 -0700 (Thu, 15 Aug 2013) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

/*! @file
    @ingroup LTC24XX_general
    Header for LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution
*/

#ifndef LTC24XX_general_H
#define LTC24XX_general_H

//! Define the SPI CS pin
#ifndef LTC24XX_CS
#define LTC24XX_CS QUIKEVAL_CS
#endif

//! In 2X Mode, A non offset binary 0 can be produced. This is corrected in the
//! differential code to voltage functions. To disable this correction, uncomment
//! The following #define. 
//#define SKIP_EZDRIVE_2X_ZERO_CHECK

/*! @name Mode Configuration for High Speed Family
 @{
*/
#define LTC24XX_HS_MULTI_KEEP_PREVIOUS_MODE              0x80
#define LTC24XX_HS_MULTI_KEEP_PREVIOUS_SPEED_RESOLUTION  0x00
#define LTC24XX_HS_MULTI_SPEED_1X                        0x00
#define LTC24XX_HS_MULTI_SPEED_2X                        0x08
/*!
 @}
*/

/*! @name Mode Configuration for EasyDrive Family
 @{
*/
// Select ADC source - differential input or PTAT circuit
#define LTC24XX_EZ_MULTI_VIN    0b10000000
#define LTC24XX_EZ_MULTI_PTAT   0b11000000

// Select rejection frequency - 50, 55, or 60Hz
#define LTC24XX_EZ_MULTI_R50    0b10010000
#define LTC24XX_EZ_MULTI_R55    0b10000000
#define LTC24XX_EZ_MULTI_R60    0b10100000

// Speed settings is bit 7 in the 2nd byte
#define LTC24XX_EZ_MULTI_SLOW   0b10000000 // slow output rate with autozero
#define LTC24XX_EZ_MULTI_FAST   0b10001000 // fast output rate with no autozero
/*!
 @}
*/


/*! @name Single-Ended Channel Configuration
@verbatim
Channel selection for all multi-channel, differential input ADCs, even those that only require
8 bits of configuration (no further options.) Most devices in this category require a second
byte of configuration for speed mode, temperature sensor selection, etc., but for the sake
of simplicity a single function will be used to read all devices, sending zeros in the second
configuration byte if only the channel is specified.

Applicable devices:
Easy Drive:
LTC2486, LTC2487, LTC2488, LTC2489, LTC2492, LTC2493,
LTC2494, LTC2495, LTC2496, LTC2497, LTC2498, LTC2499
First Generation Differential:
LTC2414, LTC2418, LTC2439
High Speed:
LTC2442, LTC2444, LTC2445, LTC2448, LTC2449
@endverbatim
@{ */
#define LTC24XX_MULTI_CH_CH0            0xB0
#define LTC24XX_MULTI_CH_CH1            0xB8
#define LTC24XX_MULTI_CH_CH2            0xB1
#define LTC24XX_MULTI_CH_CH3            0xB9
#define LTC24XX_MULTI_CH_CH4            0xB2
#define LTC24XX_MULTI_CH_CH5            0xBA
#define LTC24XX_MULTI_CH_CH6            0xB3
#define LTC24XX_MULTI_CH_CH7            0xBB
#define LTC24XX_MULTI_CH_CH8            0xB4
#define LTC24XX_MULTI_CH_CH9            0xBC
#define LTC24XX_MULTI_CH_CH10           0xB5
#define LTC24XX_MULTI_CH_CH11           0xBD
#define LTC24XX_MULTI_CH_CH12           0xB6
#define LTC24XX_MULTI_CH_CH13           0xBE
#define LTC24XX_MULTI_CH_CH14           0xB7
#define LTC24XX_MULTI_CH_CH15           0xBF
/*! @} */

/*! @name Differential Channel Configuration
@verbatim
See note for single-ended configuration above.

@endverbatim
@{ */
#define LTC24XX_MULTI_CH_P0_N1          0xA0
#define LTC24XX_MULTI_CH_P1_N0          0xA8

#define LTC24XX_MULTI_CH_P2_N3          0xA1
#define LTC24XX_MULTI_CH_P3_N2          0xA9

#define LTC24XX_MULTI_CH_P4_N5          0xA2
#define LTC24XX_MULTI_CH_P5_N4          0xAA

#define LTC24XX_MULTI_CH_P6_N7          0xA3
#define LTC24XX_MULTI_CH_P7_N6          0xAB

#define LTC24XX_MULTI_CH_P8_N9          0xA4
#define LTC24XX_MULTI_CH_P9_N8          0xAC

#define LTC24XX_MULTI_CH_P10_N11        0xA5
#define LTC24XX_MULTI_CH_P11_N10        0xAD

#define LTC24XX_MULTI_CH_P12_N13        0xA6
#define LTC24XX_MULTI_CH_P13_N12        0xAE

#define LTC24XX_MULTI_CH_P14_N15        0xA7
#define LTC24XX_MULTI_CH_P15_N14        0xAF
/*! @} */

/*Commands
Construct a channel / resolution control word by bitwise ORing one choice from the channel configuration
and one choice from the Oversample ratio configuration. You can also enable 2Xmode, which will increase
sample rate by a factor of 2 but introduce one cycle of latency.

Example - read channel 3 single-ended at OSR2048, with 2X mode enabled.
adc_command = (LTC2449_CH3 | LTC2449_OSR_2048) | LTC2449_SPEED_2X;
*/

/*! @name Oversample Ratio (OSR) Commands
@{ */
#define LTC24XX_MULTI_CH_OSR_64         0x10
#define LTC24XX_MULTI_CH_OSR_128        0x20
#define LTC24XX_MULTI_CH_OSR_256        0x30
#define LTC24XX_MULTI_CH_OSR_512        0x40
#define LTC24XX_MULTI_CH_OSR_1024       0x50
#define LTC24XX_MULTI_CH_OSR_2048       0x60
#define LTC24XX_MULTI_CH_OSR_4096       0x70
#define LTC24XX_MULTI_CH_OSR_8192       0x80
#define LTC24XX_MULTI_CH_OSR_16384      0x90
#define LTC24XX_MULTI_CH_OSR_32768      0xF0
/*! @}*/

//! Checks for EOC with a specified timeout. Applies to all SPI interface delta sigma
//! ADCs that have SINC4 rejection, does NOT apply to LTC2450/60/70 family.
//! @return Returns 0=successful, 1=unsuccessful (exceeded timeout)
int8_t LTC24XX_EOC_timeout(uint8_t cs,           //!< Chip Select pin 
                          uint16_t miso_timeout  //!< Timeout (in milliseconds)
                          );


// Read functions for SPI interface ADCs with a 32 bit output word. These functions are used with both
// Single-ended and differential parts, as there is no interpretation of the data done in
// the function. Also note that these functions can be used for devices that have shorter output lengths,
// the lower bits will read out as "1", as the conversion will be triggered by the last data bit being
// read, which causes SDO to go high.


//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_32bit_data(uint8_t cs,         //!< Chip Select pin 
                            int32_t *adc_code   //!< 4 byte conversion code read from LTC24XX
                           );

//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_8bit_command_32bit_data(uint8_t cs,               //!< Chip Select pin 
                                         uint8_t adc_command,      //!< 1 byte command written to LTC24XX
                                         int32_t *adc_code         //!< 4 byte conversion code read from LTC24XX
                                        );

//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_16bit_command_32bit_data(uint8_t cs,                  //!< Chip Select pin 
                                          uint8_t adc_command_high,    //!< First command byte written to LTC24XX
                                          uint8_t adc_command_low,     //!< Second command written to LTC24XX
                                          int32_t *adc_code            //!< 4 byte conversion code read from LTC24XX
                                         );

//! Reads from LTC24XX two channel "Ping-Pong" ADC, placing the channel information in the adc_channel parameter
//! and returning the 32 bit result with the channel bit cleared so the data format matches the rest of the family
//! @return void
void LTC24XX_SPI_2ch_ping_pong_32bit_data(uint8_t cs,           //!< Chip Select pin 
                                          uint8_t *adc_channel, //!< Returns channel number read.
                                          int32_t *code         //!< 4 byte conversion code read from LTC24XX
                                         );


// Read functions for SPI interface ADCs with a 24 bit or 19 bit output word. These functions
// are used with both Single-ended and differential parts, as there is no interpretation of
// the data done in the function. 24 bits will be read out of 19 bit devices
// (LTC2433, LTC2436, LTC2439), with the additional 5 bits being set to 1.

//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_24bit_data(uint8_t cs,         //!< Chip Select pin 
                            int32_t *adc_code   //!< 4 byte conversion code read from LTC24XX
                           );

//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_8bit_command_24bit_data(uint8_t cs,            //!< Chip Select pin 
                                         uint8_t adc_command,   //!< 1 byte command written to LTC24XX
                                         int32_t *adc_code      //!< 4 byte conversion code read from LTC24XX
                                        );

//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_16bit_command_24bit_data(uint8_t cs,                  //!< Chip Select pin 
                                          uint8_t adc_command_high,    //!< First command byte written to LTC24XX
                                          uint8_t adc_command_low,     //!< Second command written to LTC24XX
                                          int32_t *adc_code            //!< 4 byte conversion code read from LTC24XX
                                         );

//! Reads from LTC24XX ADC that accepts a 8 bit configuration and returns a 16 bit result.
//! @return  void
void LTC24XX_SPI_8bit_command_16bit_data(uint8_t cs,                //!< Chip Select pin 
                                          uint8_t adc_command,      //!< First command byte written to LTC24XX
                                          int32_t *adc_code         //!< 4 byte conversion code read from LTC24XX
                                         );                                         
                                         
                                         
//! Reads from LTC24XX two channel "Ping-Pong" ADC, placing the channel information in the adc_channel parameter
//! and returning the 32 bit result with the channel bit cleared so the data format matches the rest of the family
//! @return void
void LTC24XX_SPI_2ch_ping_pong_24bit_data(uint8_t cs,           //!< Chip Select pin 
                                          uint8_t *adc_channel, //!< Returns channel number read.
                                          int32_t *code         //!< 4 byte conversion code read from LTC24XX
                                         );

// Read functions for I2C interface ADCs with a 32 bit output word. These functions are used with both
// Single-ended and differential parts, as there is no interpretation of the data done in
// the function. Also note that these functions can be used for devices that have shorter output lengths,
// the lower bits will read out as "1", as the conversion will be triggered by the last data bit being
// read, which causes SDO to go high.
// Data is formatted to match the SPI devices, with the MSB in the bit 28 position.
// Unlike the SPI members of this family, checking for EOC MUST immediately be followed by reading the data. This
// is because a stop condition will trigger a new conversion.


//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_32bit_data(uint8_t i2c_address,  //!< I2C address of device
                            int32_t *adc_code,      //!< 4 byte conversion code read from LTC24XX
                            uint16_t eoc_timeout    //!< Timeout (in milliseconds)
                           );


//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_8bit_command_32bit_data(uint8_t i2c_address,     //!< I2C address of device
                                           uint8_t adc_command,     //!< 1 byte command written to LTC24XX
                                           int32_t *adc_code,       //!< 4 byte conversion code read from LTC24XX
                                           uint16_t eoc_timeout     //!< Timeout (in milliseconds)
                                           );


//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_16bit_command_32bit_data(uint8_t i2c_address,        //!< I2C address of device
                                            uint8_t adc_command_high,   //!< First command byte written to LTC24XX
                                            uint8_t adc_command_low,    //!< Second command written to LTC24XX
                                            int32_t *adc_code,          //!< 4 byte conversion code read from LTC24XX
                                            uint16_t eoc_timeout        //!< Timeout (in milliseconds)
                                         );


// Read functions for I2C interface ADCs with a 24 bit or 19 bit output word. These functions
// are used with both Single-ended and differential parts, as there is no interpretation of
// the data done in the function. 24 bits will be read out of 19 bit devices
// (LTC2433, LTC2436, LTC2439), with the additional 5 bits being set to 1.


//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! Applies to: LTC2483 (only this lonely one!)
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_24bit_data(uint8_t i2c_address,      //!< I2C address of device
                              int32_t *adc_code,        //!< 4 byte conversion code read from LTC24XX
                              uint16_t eoc_timeout      //!< Timeout (in milliseconds)
                             );


//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_8bit_command_24bit_data(uint8_t i2c_address,      //!< I2C address of device
                                           uint8_t adc_command,      //!< 1 byte command written to LTC24XX
                                           int32_t *adc_code,        //!< 4 byte conversion code read from LTC24XX
                                           uint16_t eoc_timeout      //!< Timeout (in milliseconds)
                                          );

//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_16bit_command_24bit_data(uint8_t i2c_address,         //!< I2C address of device
                                            uint8_t adc_command_high,    //!< First command byte written to LTC24XX
                                            uint8_t adc_command_low,     //!< Second command written to LTC24XX
                                            int32_t *adc_code,           //!< 4 byte conversion code read from LTC24XX
                                            uint16_t eoc_timeout         //!< Timeout (in milliseconds)
                                           );

//! Calculates the voltage corresponding to an ADC code, given the reference voltage.
//! Applies to Single-Ended input parts (LTC2400-type input)
//! @return Returns voltage calculated from ADC code.
float LTC24XX_SE_code_to_voltage(int32_t adc_code,  //!< Code read from ADC
                                 float vref         //!< Reference voltage
                                );
//! Calculates the voltage corresponding to an ADC code, given the reference voltage.
//! Applies to differential input parts (LTC2410 type input)
//! @return Returns voltage calculated from ADC code.
float LTC24XX_diff_code_to_voltage(int32_t adc_code,             //!< Code read from ADC
                                   float vref                    //!< Reference voltage
                                  );

//! Calculates the voltage corresponding to an ADC code, given lsb weight (in volts) and the calibrated
//! ADC offset code (zero code that is subtracted from adc_code).
//! Applies to differential input, SPI interface parts.
//! @return Returns voltage calculated from ADC code.
float LTC24XX_diff_code_to_calibrated_voltage(int32_t adc_code,               //!< Code read from ADC
                                              float LTC24XX_lsb,              //!< LSB weight (in volts)
                                              int32_t LTC24XX_offset_code     //!< The calibrated offset code (This is the ADC code zero code that will be subtracted from adc_code)
                                             );

//! Calculate the lsb weight and offset code given a full-scale code and a measured zero-code.
//! @return Void
void LTC24XX_calibrate_voltage(int32_t zero_code,             //!< Measured code with the inputs shorted to ground
                               int32_t fs_code,               //!< Measured code at nearly full-scale
                               float zero_voltage,            //!< Measured zero voltage
                               float fs_voltage,              //!< Voltage measured at input (with voltmeter) when fs_code was read from ADC
                               float *LTC24XX_lsb,            //!< Overwritten with lsb weight (in volts)
                               int32_t *LTC24XX_offset_code   //!< Overwritten with offset code (zero code)
                              );



// I2C Addresses for 8/16 channel parts (LTC2495/7/9)
//                                   ADDRESS     CA2   CA1    CA0
// #define LTC24XX_16CH_I2C_ADDRESS 0b0010100 // LOW   LOW    LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b0010110 // LOW   LOW    HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b0010101 // LOW   LOW    FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b0100110 // LOW   HIGH   LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b0110100 // LOW   HIGH   HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b0100111 // LOW   HIGH   FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b0010111 // LOW   FLOAT  LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b0100101 // LOW   FLOAT  HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b0100100 // LOW   FLOAT  FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b1010110 // HIGH  LOW    LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b1100100 // HIGH  LOW    HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b1010111 // HIGH  LOW    FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b1110100 // HIGH  HIGH   LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b1110110 // HIGH  HIGH   HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b1110101 // HIGH  HIGH   FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b1100101 // HIGH  FLOAT  LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b1100111 // HIGH  FLOAT  HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b1100110 // HIGH  FLOAT  FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b0110101 // FLOAT LOW   LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b0110111 // FLOAT LOW   HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b0110110 // FLOAT LOW   FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b1000111 // FLOAT HIGH  LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b1010101 // FLOAT HIGH  HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b1010100 // FLOAT HIGH  FLOAT
// #define LTC24XX_16CH_I2C_ADDRESS 0b1000100 // FLOAT FLOAT LOW
// #define LTC24XX_16CH_I2C_ADDRESS 0b1000110 // FLOAT FLOAT HIGH
// #define LTC24XX_16CH_I2C_ADDRESS 0b1000101 // FLOAT FLOAT FLOAT

// I2C Addresses for 2/4 channel parts
//                                  ADDRESS      CA1   CA0
// #define LTC24XX_4CH_I2C_ADDRESS 0b0010100  // LOW   LOW  
// #define LTC24XX_4CH_I2C_ADDRESS 0b0010110  // LOW   HIGH 
// #define LTC24XX_4CH_I2C_ADDRESS 0b0010101  // LOW   FLOAT
// #define LTC24XX_4CH_I2C_ADDRESS 0b0100110  // HIGH  LOW  
// #define LTC24XX_4CH_I2C_ADDRESS 0b0110100  // HIGH  HIGH 
// #define LTC24XX_4CH_I2C_ADDRESS 0b0100111  // HIGH  FLOAT
// #define LTC24XX_4CH_I2C_ADDRESS 0b0010111  // FLOAT LOW  
// #define LTC24XX_4CH_I2C_ADDRESS 0b0100101  // FLOAT HIGH 
// #define LTC24XX_4CH_I2C_ADDRESS 0b0100100  // FLOAT FLOAT
        
        
// I2C Addresses for Single channel parts (LTC2481/83/85)
//                                  ADDRESS      CA1   CA0/f0*
// #define LTC24XX_1CH_I2C_ADDRESS 0b0010100  // LOW   HIGH          
// #define LTC24XX_1CH_I2C_ADDRESS 0b0010101  // LOW   FLOAT      
// #define LTC24XX_1CH_I2C_ADDRESS 0b0010111  // FLOAT HIGH     
// #define LTC24XX_1CH_I2C_ADDRESS 0b0100100  // FLOAT FLOAT 
// #define LTC24XX_1CH_I2C_ADDRESS 0b0100110  // HIGH  HIGH         
// #define LTC24XX_1CH_I2C_ADDRESS 0b0100111  // HIGH  FLOAT     


#endif  // LTC24XX_general_H

Download LTC24XX – Linduino.CPP File

/*!
LTC24XX General Library: Functions and defines for all SINC4 Delta Sigma ADCs.

@verbatim

These functions and defines apply to all No Latency Delta Sigmas in the
LTC2480 EasyDrive family, LTC2410 differential family, LTC2400 single-ended family,
and the LTC2440 High Speed family with selectable speed / resolution.

It does not cover the LTC2450 tiny, low cost delta sigma ADC famliy.

Please refer to the No Latency Delta Sigma ADC selector guide available at:

http://www.linear.com/docs/41341


@endverbatim

http://www.linear.com/product/LTC2449

http://www.linear.com/product/LTC2449#demoboards

REVISION HISTORY
$Revision: 1807 $
$Date: 2013-07-29 13:06:06 -0700 (Mon, 29 Jul 2013) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

//! @defgroup LTC24XX LTC24XX: All no-latency delta sigma ADCs with SINC4 rejection

/*! @file
    @ingroup LTC24XX
    Library for LTC24XX no-latency delta sigma ADCs with SINC4 rejection
*/

#include <stdint.h>
#include <Arduino.h>
#include "Linduino.h"
#include <SPI.h>
#include "LT_SPI.h"
#include <Wire.h>
#include "LT_I2C.h"
#include "LTC24XX_general.h"


int8_t LTC24XX_EOC_timeout(uint8_t cs, uint16_t miso_timeout)
// Checks for EOC with a specified timeout (ms)
{
  uint16_t timer_count = 0;             // Timer count for MISO
  output_low(cs);                       //! 1) Pull CS low
  while (1)                             //! 2) Wait for SDO (MISO) to go low
  {
    if (input(MISO) == 0) break;        //! 3) If SDO is low, break loop
    if (timer_count++>miso_timeout)     // If timeout, return 1 (failure)
    {
      output_high(cs);                  // Pull CS high
      return(1);
    }
    else
      delay(1);
  }
  output_high(cs);                  // Pull CS high
  return(0);
}

// Reads from LTC24XX ADC that has no configuration word and a 32 bit output word.
void LTC24XX_SPI_32bit_data(uint8_t cs, int32_t *adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC2449 data and command
  command.LT_uint32 = 0;                // Set to zero, not necessary but avoids
                                        // random data in scope shots.
  output_low(cs);                                                       //! 1) Pull CS low
  
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)4);    //! 2) Transfer arrays

  output_high(cs);                                                      //! 3) Pull CS high
  *adc_code = data.LT_int32;
}


// Reads from a SPI LTC24XX device that has an 8 bit command and a 32 bit output word.
void LTC24XX_SPI_8bit_command_32bit_data(uint8_t cs, uint8_t adc_command, int32_t *adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC2449 data and command
  command.LT_byte[3] = adc_command;
  command.LT_byte[2] = 0;
  command.LT_byte[1] = 0;
  command.LT_byte[0] = 0;

  output_low(cs);                                                       //! 1) Pull CS low
  
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)4);    //! 2) Transfer arrays 

  output_high(cs);                                                      //! 3) Pull CS high
  *adc_code = data.LT_int32;
}


// Reads from a SPI LTC24XX device that has a 16 bit command and a 32 bit output word.
void LTC24XX_SPI_16bit_command_32bit_data(uint8_t cs, uint8_t adc_command_high, uint8_t adc_command_low, int32_t *adc_code)
{

    
  LT_union_int32_4bytes data, command;  // LTC24XX data and command
  command.LT_byte[3] = adc_command_high;
  command.LT_byte[2] = adc_command_low;
  command.LT_byte[1] = 0;
  command.LT_byte[0] = 0;
 
  output_low(cs);                                                       //! 1) Pull CS low
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)4);    //! 2) Transfer arrays 
  output_high(cs);                                                      //! 3) Pull CS high
  *adc_code = data.LT_int32;
}

//! Reads from LTC24XX two channel "Ping-Pong" ADC, placing the channel information in the adc_channel parameter
//! and returning the 32 bit result with the channel bit cleared so the data format matches the rest of the family
//! @return void
void LTC24XX_SPI_2ch_ping_pong_32bit_data(uint8_t cs, uint8_t *adc_channel, int32_t *code)
{
  LT_union_int32_4bytes data, command;      // ADC data

  command.LT_int32 = 0x00000000;  // This is a "don't care"

  spi_transfer_block(cs, command.LT_byte , data.LT_byte, (uint8_t)4);
  if(data.LT_byte[3] & 0x40) // Obtains Channel Number
  {
    *adc_channel = 1;
  }
  else
  {
    *adc_channel = 0;
  }
  data.LT_byte[3] &= 0x3F;                  // Clear channel bit here so code to voltage function doesn't have to.
  *code = data.LT_int32;                    // Return data
}

//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! @return  void
void LTC24XX_SPI_24bit_data(uint8_t cs, int32_t *adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC24XX data and command
  command.LT_int32 = 0;

  output_low(cs);                                                       //! 1) Pull CS low
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)3);    //! 2) Transfer arrays 
  output_high(cs);                                                      //! 3) Pull CS high

  data.LT_byte[3] = data.LT_byte[2]; // Shift bytes up by one. We read out 24 bits,
  data.LT_byte[2] = data.LT_byte[1]; // which are loaded into bytes 2,1,0. Need to left-
  data.LT_byte[1] = data.LT_byte[0]; // justify.
  data.LT_byte[0] = 0x00;

  *adc_code = data.LT_int32;
}

//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 24 bit output word.
//! @return  void
void LTC24XX_SPI_8bit_command_24bit_data(uint8_t cs, uint8_t adc_command, int32_t *adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC24XX data and command
  command.LT_byte[2] = adc_command;
  command.LT_byte[1] = 0;
  command.LT_byte[0] = 0;

  output_low(cs);                                                       //! 1) Pull CS low
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)3);    //! 2) Transfer arrays 
  output_high(cs);                                                      //! 3) Pull CS high

  data.LT_byte[3] = data.LT_byte[2]; // Shift bytes up by one. We read out 24 bits,
  data.LT_byte[2] = data.LT_byte[1]; // which are loaded into bytes 2,1,0. Need to left-
  data.LT_byte[1] = data.LT_byte[0]; // justify.
  data.LT_byte[0] = 0x00;

  *adc_code = data.LT_int32;
}

//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 24 bit output word.
//! @return  void
void LTC24XX_SPI_16bit_command_24bit_data(uint8_t cs, uint8_t adc_command_high, uint8_t adc_command_low, int32_t *adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC24XX data and command
  command.LT_byte[2] = adc_command_high;
  command.LT_byte[1] = adc_command_low;
  command.LT_byte[0] = 0;
  
  
  output_low(cs);                                                       //! 1) Pull CS low
  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)3);    //! 2) Transfer arrays 
  output_high(cs);                                                      //! 3) Pull CS high

  data.LT_byte[3] = data.LT_byte[2]; // Shift bytes up by one. We read out 24 bits,
  data.LT_byte[2] = data.LT_byte[1]; // which are loaded into bytes 2,1,0. Need to left-
  data.LT_byte[1] = data.LT_byte[0]; // justify.
  data.LT_byte[0] = 0x00;

  *adc_code = data.LT_int32;
}

//! Reads from LTC24XX two channel "Ping-Pong" ADC, placing the channel information in the adc_channel parameter
//! and returning the 24 bit result with the channel bit cleared so the data format matches the rest of the family
//! @return void
void LTC24XX_SPI_2ch_ping_pong_24bit_data(uint8_t cs, uint8_t *adc_channel, int32_t *code)
{
  LT_union_int32_4bytes data, command;      // ADC data

  command.LT_int32 = 0x00000000;  // This is a "don't care"

  spi_transfer_block(cs, command.LT_byte , data.LT_byte, (uint8_t)3);
  data.LT_byte[3] = data.LT_byte[2]; // Shift bytes up by one. We read out 24 bits,
  data.LT_byte[2] = data.LT_byte[1]; // which are loaded into bytes 2,1,0. Need to left-
  data.LT_byte[1] = data.LT_byte[0]; // justify.
  data.LT_byte[0] = 0x00;

  if(data.LT_byte[3] & 0x40) // Obtains Channel Number
  {
    *adc_channel = 1;
  }
  else
  {
    *adc_channel = 0;
  }
  data.LT_byte[3] &= 0x3F;                  // Clear channel bit here so code to voltage function doesn't have to.
  *code = data.LT_int32;                    // Return data
}


//I2C functions

//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 24 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_8bit_command_24bit_data(uint8_t i2c_address, uint8_t adc_command, int32_t *adc_code, uint16_t eoc_timeout)
{
  int8_t ack;
  uint16_t timer_count = 0;        // Timer count to wait for ACK
  int8_t buf[4];
  LT_union_int32_4bytes data;      // LTC24XX data
  while(1)
  {
    ack = i2c_read_block_data(i2c_address, adc_command, 3, data.LT_byte);
    if(!ack) break; // !ack indicates success
    if (timer_count++>eoc_timeout)     // If timeout, return 1 (failure)
      return(1);
    else
      delay(1);
  }
  data.LT_byte[3] = data.LT_byte[2]; // Shift bytes up by one. We read out 24 bits,
  data.LT_byte[2] = data.LT_byte[1]; // which are loaded into bytes 2,1,0. Need to left-
  data.LT_byte[1] = data.LT_byte[0]; // justify.
  data.LT_byte[0] = 0x00;
  data.LT_uint32 >>= 2;  // Shifts data 2 bits to the right; operating on unsigned member shifts in zeros.
  data.LT_byte[3] = data.LT_byte[3] & 0x3F; // Clear upper 2 bits JUST IN CASE. Now the data format matches the SPI parts.
  *adc_code = data.LT_int32;
  return(ack); // Success
}



//! Reads from LTC24XX ADC that has no configuration word and returns a 32 bit result.
//! Data is formatted to match the SPI devices, with the MSB in the bit 28 position.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_32bit_data(uint8_t i2c_address,                   //!< I2C address of device
                            int32_t *adc_code,                      //!< 4 byte conversion code read from LTC24XX
                            uint16_t eoc_timeout                     //!< Timeout (in milliseconds)
                           )
{
  int8_t ack;
  uint16_t timer_count = 0;        // Timer count to wait for ACK
  int8_t buf[4];
  LT_union_int32_4bytes data;      // LTC24XX data
  while(1)
  {
    ack = i2c_read_block_data(i2c_address, 4, data.LT_byte);
    if(!ack) break; // !ack indicates success
    if (timer_count++>eoc_timeout)     // If timeout, return 1 (failure)
      return(1);
    else
      delay(1);
  }

  data.LT_uint32 >>= 2;  // Shifts data 2 bits to the right; operating on unsigned member shifts in zeros.
  data.LT_byte[3] = data.LT_byte[3] & 0x3F; // Clear upper 2 bits JUST IN CASE. Now the data format matches the SPI parts.
  *adc_code = data.LT_int32;
  return(ack); // Success
  }


//! Reads from LTC24XX ADC that accepts an 8 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_8bit_command_32bit_data(uint8_t i2c_address, uint8_t adc_command, int32_t *adc_code, uint16_t eoc_timeout)
{
  int8_t ack;
  uint16_t timer_count = 0;        // Timer count to wait for ACK
  int8_t buf[4];
  LT_union_int32_4bytes data;      // LTC24XX data
  while(1)
  {
    ack = i2c_read_block_data(i2c_address, adc_command, 4, data.LT_byte);
    if(!ack) break; // !ack indicates success
    if (timer_count++>eoc_timeout)     // If timeout, return 1 (failure)
      return(1);
    else
      delay(1);
  }

  data.LT_uint32 >>= 2;  // Shifts data 2 bits to the right; operating on unsigned member shifts in zeros.
  data.LT_byte[3] = data.LT_byte[3] & 0x3F; // Clear upper 2 bits JUST IN CASE. Now the data format matches the SPI parts.
  *adc_code = data.LT_int32;
  return(ack); // Success
}

//! Reads from LTC24XX ADC that accepts a 16 bit configuration and returns a 32 bit result.
//! @return  Returns the state of the acknowledge bit after the I2C address write. 0=acknowledge, 1=no acknowledge.
int8_t LTC24XX_I2C_16bit_command_32bit_data(uint8_t i2c_address,uint8_t adc_command_high,
                                            uint8_t adc_command_low,int32_t *adc_code,uint16_t eoc_timeout)
{
  int8_t ack;
  uint16_t adc_command, timer_count = 0;        // Timer count to wait for ACK
  int8_t buf[4];
  LT_union_int32_4bytes data;      // LTC24XX data
  adc_command = (adc_command_high << 8) | adc_command_low;
  while(1)
  {
    ack = i2c_two_byte_command_read_block(i2c_address, adc_command, 4, data.LT_byte);
    if(!ack) break; // !ack indicates success
    if (timer_count++>eoc_timeout)     // If timeout, return 1 (failure)
      return(1);
    else
      delay(1);
  }

  data.LT_uint32 >>= 2;  // Shifts data 2 bits to the right; operating on unsigned member shifts in zeros.
  data.LT_byte[3] = data.LT_byte[3] & 0x3F; // Clear upper 2 bits JUST IN CASE. Now the data format matches the SPI parts.
  *adc_code = data.LT_int32;
  return(ack); // Success
}

// Calculates the voltage corresponding to an adc code, given the reference voltage (in volts)
float LTC24XX_SE_code_to_voltage(int32_t adc_code, float vref)
{
  float voltage;
  adc_code -= 0x20000000;             //! 1) Subtract offset
  voltage=(float) adc_code;
  voltage = voltage / 268435456.0;    //! 2) This calculates the input as a fraction of the reference voltage (dimensionless)
  voltage = voltage * vref;           //! 3) Multiply fraction by Vref to get the actual voltage at the input (in volts)
  return(voltage);
}

// Calculates the voltage corresponding to an adc code, given the reference voltage (in volts)
// This function handles all differential input parts, including the "single-ended" mode on multichannel
// differential parts. Data from I2C parts must be right-shifted by two bit positions such that the MSB
// is in bit 28 (the same as the SPI parts.)
float LTC24XX_diff_code_to_voltage(int32_t adc_code, float vref)
{
  float voltage;
  
  #ifndef SKIP_EZDRIVE_2X_ZERO_CHECK
  if(adc_code == 0x00000000)
  {
    adc_code = 0x20000000;
  }
  #endif

  adc_code -= 0x20000000;             //! 1) Converts offset binary to binary
  voltage=(float) adc_code;
  voltage = voltage / 536870912.0;    //! 2) This calculates the input as a fraction of the reference voltage (dimensionless)
  voltage = voltage * vref;           //! 3) Multiply fraction by Vref to get the actual voltage at the input (in volts)
  return(voltage);
}

// Calculates the voltage corresponding to an adc code, given lsb weight (in volts) and the calibrated
// adc offset code (zero code that is subtracted from adc_code). For use with the LTC24XX_cal_voltage() function.
float LTC24XX_diff_code_to_calibrated_voltage(int32_t adc_code, float LTC2449_lsb, int32_t LTC2449_offset_code)
{
  float adc_voltage;
  
  #ifndef SKIP_EZDRIVE_2X_ZERO_CHECK
  if(adc_code == 0x00000000)
  {
    adc_code = 0x20000000;
  }
  #endif  
  
  adc_code -= 536870912;                                            //! 1) Converts offset binary to binary
  adc_voltage=(float)(adc_code+LTC2449_offset_code)*LTC2449_lsb;    //! 2) Calculate voltage from ADC code, lsb, offset.
  return(adc_voltage);
}


// Calculate the lsb weight and offset code given a full-scale code and a measured zero-code.
void LTC24XX_calibrate_voltage(int32_t zero_code, int32_t fs_code, float zero_voltage, float fs_voltage, float *LTC24XX_lsb, int32_t *LTC24XX_offset_code)
{
  zero_code -= 536870912;   //! 1) Converts zero code from offset binary to binary
  fs_code -= 536870912;     //! 2) Converts full scale code from offset binary to binary
  
  float temp_offset;
  *LTC24XX_lsb = (fs_voltage-zero_voltage)/((float)(fs_code - zero_code));                              //! 3) Calculate the LSB
  
  temp_offset = (zero_voltage/ *LTC24XX_lsb) - zero_code;                                               //! 4) Calculate Unipolar offset
  temp_offset = (temp_offset > (floor(temp_offset) + 0.5)) ? ceil(temp_offset) : floor(temp_offset);    //! 5) Round
  *LTC24XX_offset_code = (int32_t)temp_offset;                                                          //! 6) Cast as int32_t
}

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