LTC2411 - 24-Bit No Latency Delta Sigma ADC with Differential Input and Reference in MSOP

/*!
Linear Technology DC571A Demonstration Board.
LTC2418: 24-bit No Latency Delta Sigma 16-channel ADC

@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. No external power supply is required. Ensure all jumpers on 
    the demo board are installed in their default positions from the 
    factory.

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

  How to calibrate:
    Apply 100mV to CH0 with respect to COM pin. Next, Measure this voltage with a 
    precise voltmeter and enter this value. (This takes the reading.) Apply a higher 
    voltage than the first voltage or approximately 2.40 volts to CH0. Anything
    above 2.40 is not reccomened. It is very likely to reach the ADC's full-scale
    and poduce invalide lsb and offset. Measure this voltage with a precise
    voltmeter and enter this value. Calibration is now stored in EEPROM. Upon
    startup the calibration values will be restored.

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

@endverbatim

http://www.linear.com/product/LTC2418

http://www.linear.com/product/LTC2418#demoboards

REVISION HISTORY
$Revision: 1886 $
$Date: 2013-08-15 16:29:46 -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 LTC2418
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "LT_I2C.h"
#include "UserInterface.h"
#include "QuikEval_EEPROM.h"
#include "LTC2418.h"
#include <SPI.h>
#include <Wire.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
void store_calibration();                           // store the ADC calibration to the EEPROM
int8_t restore_calibration();                       // read the calibration from EEPROM return 1 if successful, 0 if not

int8_t menu_1_read_single_ended();
int8_t menu_2_read_differential();
int8_t menu_3_calibrate();

// Global variables
static uint8_t demo_board_connected;                //!< Set to 1 if the board is connected
static float LTC2418_lsb = 5.9604652E-7;            //!< Ideal LSB voltage for a perfect part
static int32_t LTC2418_offset_code = 0;             //!< Ideal offset for a perfect part


//Constants
//! Lookup table to build the command for single-ended mode channels
const uint8_t BUILD_COMMAND_SINGLE_ENDED[16] = {LTC2418_CH0, LTC2418_CH1, LTC2418_CH2, LTC2418_CH3,
    LTC2418_CH4, LTC2418_CH5, LTC2418_CH6, LTC2418_CH7,
    LTC2418_CH8, LTC2418_CH9, LTC2418_CH10, LTC2418_CH11,
    LTC2418_CH12, LTC2418_CH13, LTC2418_CH14, LTC2418_CH15
                                               };   //!< Builds the command for single-ended mode

//! Lookup table to build the command for differential mode channels
const uint8_t BUILD_COMMAND_DIFF[16] = {LTC2418_P0_N1, LTC2418_P2_N3, LTC2418_P4_N5, LTC2418_P6_N7,
                                        LTC2418_P8_N9, LTC2418_P10_N11, LTC2418_P12_N13, LTC2418_P14_N15,
                                        LTC2418_P1_N0, LTC2418_P3_N2, LTC2418_P5_N4, LTC2418_P7_N6,
                                        LTC2418_P9_N8, LTC2418_P11_N10, LTC2418_P13_N12, LTC2418_P15_N14
                                       };           //!< Build the command for differential

const uint16_t MISO_TIMEOUT = 1000;                 //!< The MISO timeout (ms)

//! Initialize Linduino
void setup()
{
  char demo_name[6]="DC571";        // Demo Board Name stored in QuikEval EEPROM
  quikeval_SPI_init();              // Configure the spi port for 4MHz SCK
  quikeval_SPI_connect();           // Connect SPI to main data port
  quikeval_I2C_init();              // Configure the EEPROM I2C port for 100kHz
  Serial.begin(115200);             // Initialize the serial port to the PC
  print_title();
  demo_board_connected = discover_demo_board(demo_name);
  if (!(demo_board_connected))      // Resolves EEPROM string variation
  {
    Serial.print(F("Checking for string variation\n"));
    demo_name[0]='D';
    demo_name[1]='C';
    demo_name[2]='5';
    demo_name[3]='7';
    demo_name[4]='1';
    demo_name[5]='-';
    demo_board_connected = discover_demo_board(demo_name);
  }
  if (demo_board_connected)
  {
    restore_calibration();
    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
      switch (user_command)
      {
        case 1:
          acknowledge |= menu_1_read_single_ended();
          break;
        case 2:
          acknowledge |= menu_2_read_differential();
          break;
        case 3:
          acknowledge |= menu_3_calibrate();
          break;
        default:
          Serial.println("Incorrect Option");
          break;
      }
      if(acknowledge)
        Serial.println(F("***** SPI ERROR ******"));
      Serial.print(F("\n*************************\n"));
      print_prompt();
    }
  }
}

// Function Definitions

//! Read channels in single-ended mode
//! @return 0 when m is entered into menu, 1 if timeout for EOC
int8_t menu_1_read_single_ended()
{
  uint8_t  adc_command; // The LTC2418 command byte
  int16_t user_command; // The user input command
  uint32_t adc_code;    // The LTC2418 code
  float adc_voltage;    // The LTC2418 voltage

  while (1)
  {
    Serial.print(F("*************************\n\n"));      // Display single-ended menu
    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("\nEnter a Command: "));
    user_command = read_int();                              // Read the single command
    if (user_command == 'm')
      return(0);
    else
      Serial.println(user_command);
    Serial.println();

    if (user_command == 16)
    {
      Serial.print(F("ALL\n"));
      adc_command = BUILD_COMMAND_SINGLE_ENDED[0];          // Build ADC command for channel 0
      
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throws out last reading

      for (int8_t x = 0; x < 15; x++)
      {
        adc_command = BUILD_COMMAND_SINGLE_ENDED[(x + 1) % 16]; // Read all channels in single-ended mode
        if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))        // Check for EOC
          return(1);
        LTC2418_read(LTC2418_CS, adc_command, &adc_code);
        adc_voltage = LTC2418_code_to_voltage(adc_code, LTC2418_lsb , LTC2418_offset_code);
        Serial.print(F("  ****"));
        Serial.print(F("CH"));
        Serial.print(x);
        Serial.print(F(": "));
        Serial.print(adc_voltage, 4);
        Serial.print(F("V\n"));
      }
    }
    else if (user_command != 'm')                           // Read selected channel
    {
      adc_command = BUILD_COMMAND_SINGLE_ENDED[user_command];
      Serial.print(F("\nADC Command: B"));
      Serial.println(adc_command, BIN);
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throws out last reading
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);
      Serial.print(F("Received Code: 0x"));
      Serial.println(adc_code, HEX);
      adc_voltage = LTC2418_code_to_voltage(adc_code, LTC2418_lsb , LTC2418_offset_code);
      Serial.print(F("  ****"));
      Serial.print(F("CH"));
      Serial.print(user_command);
      Serial.print(F(": "));
      Serial.print(adc_voltage, 4);
      Serial.print(F("V\n"));
    }
  }
}

//! Read channels in differential mode
//! @return 0 when m is entered into menu, 1 if timeout for EOC
int8_t menu_2_read_differential()
{
  int8_t y;             // Offset into differential channel array to select polarity
  uint8_t  adc_command; // The LTC2418 command byte
  int16_t user_command; // The user input command
  uint32_t adc_code;    // The LTC2418 code
  float adc_voltage;    // The LTC2418 voltage

  while (1)
  {
    // Display differential menu
    Serial.print(F("\n*************************\n\n"));
    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"));
    Serial.print(F("\nEnter a Command: "));
    user_command = read_int();
    if (user_command == 'm')
      return(0);
    Serial.println(user_command);
    Serial.println();

    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];                  // Set up first channel
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throws out last reading
      for (int8_t x = 0; x <= 7; x++)                       // Read all channels. All even channels are positive and odd channels are negative
      {
        adc_command = BUILD_COMMAND_DIFF[((x+1) % 8) + y];
        if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))    // Check for EOC
          return(1);
        LTC2418_read(LTC2418_CS, adc_command, &adc_code);
        adc_voltage = LTC2418_code_to_voltage(adc_code, LTC2418_lsb , LTC2418_offset_code);
        Serial.println();
        Serial.print(F("  ****"));
        print_user_command(x + y);
        Serial.print(F(": "));
        Serial.print(adc_voltage, 4);
        Serial.print(F("V\n"));
      }
    }
    else                                                    // Read selected channels
    {
      // Reads and displays a selected channel
      adc_command = BUILD_COMMAND_DIFF[user_command];
      Serial.print(F("ADC Command: B"));
      Serial.println(adc_command, BIN);
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throws out last reading
      if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
        return(1);
      LTC2418_read(LTC2418_CS, adc_command, &adc_code);
      Serial.print(F("Received Code: 0x"));
      Serial.println(adc_code, HEX);
      adc_voltage = LTC2418_code_to_voltage(adc_code, LTC2418_lsb , LTC2418_offset_code);
      Serial.println();
      Serial.print(F("  ****"));
      Serial.print(F("CH"));
      Serial.print(user_command);
      Serial.print(F(": "));
      Serial.print(adc_voltage, 4);
      Serial.print(F("V"));
      Serial.println();
    }
  }
}

//! Calibrate ADC given two known inputs
//! @return 0 if successful, 1 if timeout for EOC
int8_t menu_3_calibrate()
{
  // Calibration
  float fs_voltage;     // Measured full-scale voltage
  float zero_voltage;   // Measured zero voltage
  uint32_t zero_code;   // Cal zero code
  uint32_t fs_code;     // Cal full scale code
  uint8_t  adc_command; // The LTC2418 command byte
  uint32_t adc_code;    // The LTC2418 code

  Serial.println("Apply  100mV to CH0 with respect to COM");
  Serial.println("or apply a voltage greater than GND for the");
  Serial.println("lower point in two point calibration");
  Serial.print("Enter the measured input voltage:");
  zero_voltage = read_float();
  Serial.println(zero_voltage,4);
  adc_command = BUILD_COMMAND_SINGLE_ENDED[0];          // Build ADC command byte for voltage input
  if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
    return(1);
  LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throw away previous reading
  delay(100);
  if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
    return(1);
  LTC2418_read(LTC2418_CS, adc_command, &zero_code);    // Measure zero

  Serial.println("Apply ~2.40V input voltage to CH0");
  Serial.println("or apply a voltage greater that first");
  Serial.println("voltage and less than 2.40V.");
  Serial.print("Enter the measured input voltage: ");

  fs_voltage = read_float();
  Serial.println(fs_voltage, 4);
  adc_command = BUILD_COMMAND_SINGLE_ENDED[0];          // Build ADC command byte for voltage input
  if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
    return(1);
  LTC2418_read(LTC2418_CS, adc_command, &adc_code);     // Throw away previous reading
  delay(100);
  if(LTC2418_EOC_timeout(LTC2418_CS, MISO_TIMEOUT))      // Check for EOC
    return(1);
  LTC2418_read(LTC2418_CS, adc_command, &fs_code);      // Measure full scale
  LTC2418_cal_voltage(zero_code, fs_code, zero_voltage, fs_voltage, &LTC2418_lsb , &LTC2418_offset_code);

  Serial.print("ADC offset : ");
  Serial.println(LTC2418_offset_code);
  Serial.print("ADC lsb : ");
  Serial.print(LTC2418_lsb*1.0e9, 4);
  Serial.println("nV (32-bits)");
  store_calibration();
  return(0);
}

//! Prints the title block when program first starts.
void print_title()
{
  Serial.print(F("\n*****************************************************************\n"));
  Serial.print(F("* DC571A 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 24-bit ADC.                                          *\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-Calibration\n"));
  Serial.println();
  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("0P-1N");
      break;
    case 1:
      Serial.print("2P-3N");
      break;
    case 2:
      Serial.print("4P-5N");
      break;
    case 3:
      Serial.print("6P-7N");
      break;
    case 4:
      Serial.print("8P-9N");
      break;
    case 5:
      Serial.print("10P-11N");
      break;
    case 6:
      Serial.print("12P-13N");
      break;
    case 7:
      Serial.print("14P-15N");
      break;
    case 8:
      Serial.print("1P-0N");
      break;
    case 9:
      Serial.print("3P-2N");
      break;
    case 10:
      Serial.print("5P-4N");
      break;
    case 11:
      Serial.print("7P-6N");
      break;
    case 12:
      Serial.print("9P-8N");
      break;
    case 13:
      Serial.print("11P-10N");
      break;
    case 14:
      Serial.print("13P-12N");
      break;
    case 15:
      Serial.print("15P-14N");
      break;
  }
  Serial.print(": ");
}

//! Store measured calibration parameters to nonvolatile EEPROM on demo board
void store_calibration()
// store the ADC calibration to the EEPROM
{
  eeprom_write_int16(EEPROM_I2C_ADDRESS, EEPROM_CAL_KEY, EEPROM_CAL_STATUS_ADDRESS);          // Cal key
  eeprom_write_int32(EEPROM_I2C_ADDRESS, LTC2418_offset_code, EEPROM_CAL_STATUS_ADDRESS+2);   // Offset
  eeprom_write_float(EEPROM_I2C_ADDRESS, LTC2418_lsb, EEPROM_CAL_STATUS_ADDRESS+6);           // LSB
  Serial.println("Calibration Stored to EEPROM");
}

//! Read stored calibration parameters from nonvolatile EEPROM on demo board
//! @return return 1 if successful, 0 if not
int8_t restore_calibration()
{
  int16_t cal_key;
  // read the cal key from the EEPROM
  eeprom_read_int16(EEPROM_I2C_ADDRESS, &cal_key, EEPROM_CAL_STATUS_ADDRESS);
  if (cal_key == EEPROM_CAL_KEY)
  {
    // calibration has been stored, read offset and lsb
    eeprom_read_int32(EEPROM_I2C_ADDRESS, &LTC2418_offset_code, EEPROM_CAL_STATUS_ADDRESS+2);  // Offset
    eeprom_read_float(EEPROM_I2C_ADDRESS, &LTC2418_lsb, EEPROM_CAL_STATUS_ADDRESS+6);          // LSB
    Serial.println("Calibration Restored");
    return(1);
  }
  else
  {
    Serial.println("Calibration not found");
    return(0);
  }
}

/*!
LTC2418: LTC2418 - 16-Channel 24-Bit No Latency Delta-Sigma ADC

@verbatim

The LTC2414/LTC2418 are 8-/16-channel (4-/8-differential) micropower 24-bit 
delta-sigma analog-to-digital converters. They operate from 2.7V to 5.5V and 
include an integrated oscillator, 2ppm INL and 0.2ppm RMS noise. They use 
delta-sigma technology and provide single cycle settling time for multiplexed 
applications. Through a single pin, the LTC2414/LTC2418 can be configured for 
better than 110dB differential mode rejection at 50Hz or 60Hz +/-2%, or they can 
be driven by an external oscillator for a user-defined rejection frequency. The 
internal oscillator requires no external frequency setting components. 

@endverbatim

http://www.linear.com/product/LTC2418

http://www.linear.com/product/LTC2418#demoboards

REVISION HISTORY
$Revision: 1861 $
$Date: 2013-08-13 09:48:57 -0700 (Tue, 13 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.
*/

//! @defgroup LTC2418 LTC2418: 16-Channel 24-Bit No Latency Delta-Sigma ADC

/*! @file
    @ingroup LTC2418
    Library for LTC2418: 16-Channel 24-Bit No Latency Delta-Sigma ADC
*/

#include <stdint.h>
#include <Arduino.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "LTC2418.h"
#include <SPI.h>

int8_t LTC2418_EOC_timeout(uint8_t cs, uint16_t miso_timeout)
// Checks for EOC with a specified timeout
{
  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);
  }
  return(0);
}
  
void LTC2418_read(uint8_t cs, uint8_t adc_command, uint32_t *adc_code)
// Reads the LTC2418
{
  LT_union_int32_4bytes data, 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 4 bytes
  output_high(cs);                                                      //! 3) Pull CS high
  *adc_code = data.LT_int32;
}

float LTC2418_code_to_voltage(int32_t adc_code, float LTC2418_lsb , int32_t LTC2418_offset_code)
// Calculates the LTC2418 input bipolar voltage
{
  float adc_voltage;
  adc_code = adc_code>>6;                                           //! 1) Bit-shift ADC code to the right 6 bits
  adc_code -= 8388608;                                              //! 2) Convert ADC code from offset binary to binary
  adc_voltage=((float)adc_code+LTC2418_offset_code)*(LTC2418_lsb);  //! 3) Calculate voltage from ADC code, lsb, offset.
  return(adc_voltage);
}

void LTC2418_cal_voltage(int32_t zero_code, int32_t fs_code, float zero_voltage, float fs_voltage, float *LTC2418_lsb , int32_t *LTC2418_offset_code)
// Calibrate the lsb
{
  zero_code = zero_code >> 6;   //! 1) Bit-shift zero code to the right 6 bits
  zero_code -= 8388608;         //! 2) Convert zero code from offset binary to binary
  fs_code = fs_code >> 6;       //! 3) Bit-shift full scale code to the right 6 bits
  fs_code -= 8388608;           //! 4) Convert full scale code from offset binary to binary
  
  float temp_offset;
  *LTC2418_lsb = (fs_voltage-zero_voltage)/((float)(fs_code - zero_code));                              //! 5) Calculate the LSB
  
  temp_offset = (zero_voltage/ *LTC2418_lsb) - zero_code;                                               //! 6) Calculate Unipolar offset
  temp_offset = (temp_offset > (floor(temp_offset) + 0.5)) ? ceil(temp_offset) : floor(temp_offset);    //! 7) Round
  *LTC2418_offset_code = (int32_t)temp_offset;                                                          //! 8) Cast as int32_t
}

/*!
LTC2418: 16-Channel 24-Bit No Latency Delta-Sigma ADC

@verbatim

The LTC2414/LTC2418 are 8-/16-channel (4-/8-differential) micropower 24-bit 
delta-sigma analog-to-digital converters. They operate from 2.7V to 5.5V and 
include an integrated oscillator, 2ppm INL and 0.2ppm RMS noise. They use 
delta-sigma technology and provide single cycle settling time for multiplexed 
applications. Through a single pin, the LTC2414/LTC2418 can be configured for 
better than 110dB differential mode rejection at 50Hz or 60Hz +/-2%, or they can 
be driven by an external oscillator for a user-defined rejection frequency. The 
internal oscillator requires no external frequency setting components. 

SPI DATA FORMAT (MSB First):

            Byte #1                            Byte #2                           Byte #3                    Byte #4

Data Out :  !EOC DMY SIG D22 D21 D20 D19 D18   D17 D16 D15 D14 D13 D12 D11 D10   D9 D8 D7 D6 D5 D4 D3  D2   D1 D0 SGL OS S2 S1 S0 PAR
Data In  :  1    0   EN  SGL OS  S2  S1  S0    X   X   X   X   X   X   X   X     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
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
PAR  : Parity Bit

Command Byte
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


Example Code:

Read Channel 0 in Single-Ended mode
    
    uint16_t miso_timeout = 1000;
    adc_command = LTC2418_CH0;                          // Build ADC command for channel 0
    
    if(LTC2418_EOC_timeout(LTC2418_CS, miso_timeout))    // Check for EOC
        return(1);
    LTC2418_read(LTC2418_CS, adc_command, &adc_code);   // Throws out last reading
    
    if(LTC2418_EOC_timeout(LTC2418_CS, miso_timeout))    // Check for EOC
        return(1);
    LTC2418_read(LTC2418_CS, adc_command, &adc_code);   // Obtains the current reading and stores to adc_code variable

    // Convert adc_code to voltage
    adc_voltage = LTC2418_code_to_voltage(adc_code, LTC2418_lsb , LTC2418_offset_code);

@endverbatim

http://www.linear.com/product/LTC2418

http://www.linear.com/product/LTC2418#demoboards

REVISION HISTORY
$Revision: 1853 $
$Date: 2013-08-08 17:01:29 -0700 (Thu, 08 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 LTC2418
    Header for LTC2418: 16-Channel 24-Bit No Latency Delta-Sigma ADC
*/

#ifndef LTC2418_H
#define LTC2418_H

#include <SPI.h>

//! Define the SPI CS pin
#ifndef LTC2418_CS
#define LTC2418_CS QUIKEVAL_CS
#endif

//! @name LTC2418 Single-Ended configuration bytes
//! @{
//! Address bytes with enable sequence prepended
#define LTC2418_CH0            0xB0
#define LTC2418_CH1            0xB8
#define LTC2418_CH2            0xB1
#define LTC2418_CH3            0xB9
#define LTC2418_CH4            0xB2
#define LTC2418_CH5            0xBA
#define LTC2418_CH6            0xB3
#define LTC2418_CH7            0xBB
#define LTC2418_CH8            0xB4
#define LTC2418_CH9            0xBC
#define LTC2418_CH10           0xB5
#define LTC2418_CH11           0xBD
#define LTC2418_CH12           0xB6
#define LTC2418_CH13           0xBE
#define LTC2418_CH14           0xB7
#define LTC2418_CH15           0xBF
//! @}

//! @name LTC2418 Differential configuration bytes
//! @{
//! Address bytes with enable sequence prepended
#define LTC2418_P0_N1          0xA0
#define LTC2418_P1_N0          0xA8

#define LTC2418_P2_N3          0xA1
#define LTC2418_P3_N2          0xA9

#define LTC2418_P4_N5          0xA2
#define LTC2418_P5_N4          0xAA

#define LTC2418_P6_N7          0xA3
#define LTC2418_P7_N6          0xAB

#define LTC2418_P8_N9          0xA4
#define LTC2418_P9_N8          0xAC

#define LTC2418_P10_N11        0xA5
#define LTC2418_P11_N10        0xAD

#define LTC2418_P12_N13        0xA6
#define LTC2418_P13_N12        0xAE

#define LTC2418_P14_N15        0xA7
#define LTC2418_P15_N14        0xAF
//! @}

//! Checks for EOC with a specified timeout
//! @return 0=successful, 1=unsuccessful (exceeded timeout)
int8_t LTC2418_EOC_timeout(uint8_t cs,           //!< Chip Select pin 
                           uint16_t miso_timeout //!< Timeout (ms)
                          );

//! Reads the LTC2418 result and programs the configuration for the next conversion.
//! @return void
void LTC2418_read(uint8_t cs,           //!< Chip Select pin
                  uint8_t adc_command,  //!< Command byte
                  uint32_t *adc_code    //!< Returns raw 32-bit code read from ADC
                 );

//! Calculates the LTC2418 input bipolar voltage
//! @return Calculated voltage
float LTC2418_code_to_voltage(int32_t adc_code,           //!< Raw ADC code
                              float LTC2418_lsb,          //!< LSB value (volts)
                              int32_t LTC2418_offset_code //!< Offset (Code)
                             );

//! Calibrate the lsb
//! @return Void
void LTC2418_cal_voltage(int32_t zero_code,               //!< Offset (Code)
                         int32_t fs_code,                 //!< Code measured with full-scale input applied
                         float zero_voltage,              //!< Measured zero voltage
                         float fs_voltage,                //!< Measured full-scale voltage
                         float *LTC2418_lsb,              //!< Returns LSB value (volts)
                         int32_t *LTC2418_offset_code     //!< Returns Offset (Code)
                        );

#endif  // LTC2418_H