LTC2308 - Low Noise, 500ksps, 8-Channel, 12-Bit ADC

/*!
Linear Technology DC1186A Demonstration Board.
LTC2308: 12-Bit, 8-Channel 500ksps SAR ADC with SPI Interface.

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator. Equipment
   required is a voltage source (preferably low-noise) 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. Refer to Demo Manual 
   DC1186A.

  How to test Single-Ended mode:
   Bipolar Mode:
    The voltage source should be connected to one of the inputs CH0,...CH7. Ensure the input is
    within its specified absolute input voltage range. (It is easiest
    to tie the voltage source negative terminal to COM.) Ensure the voltage
    source is set within the range of 0V to +4.096V.
    (Swapping input voltages results in a reversed polarity reading.)

   Unipolar Mode:
    The voltage source should be connected to one of the inputs CH0,...CH7. Ensure the input is
    within its specified absolute input voltage range. (It is easiest
    to tie the voltage source negative terminal to COM.) Ensure the voltage
    source is set within the range of 0V to +4.096V.
   
  How to test Differential Mode:
   Bipolar Mode:
     The voltage source should be connected between paired channels. Ensure both
     inputs are within their specified absolute input voltage range. (It is easiest
     to tie the voltage source negative terminal to COM or GND.) Ensure the voltage
     source is set within the range of 0 to +4.096V (differential voltage range).
     (Swapping input voltages results in a reversed polarity reading.)

   Unipolar Mode:
     The voltage source should be connected between paired channels. (It is easiest
     to tie the voltage source negative terminal to COM or GND.) Ensure both inputs
     are within their specified absolute input voltage range.  (It is easiest to tie
     the voltage source negative terminal to COM or GND.) Ensure the voltage source
     is set within the range of 0 to +4.096V (differential voltage range).

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

@endverbatim

http://www.linear.com/product/LTC2308

http://www.linear.com/product/LTC2308#demoboards

REVISION HISTORY
$Revision: 3018 $
$Date: 2014-12-01 15:53:20 -0800 (Mon, 01 Dec 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 LTC2308
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "UserInterface.h"
#include "LT_I2C.h"
#include "QuikEval_EEPROM.h"
#include "LTC2308.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
uint8_t print_user_command_differential();             // Display selected differential channels
uint8_t print_user_command_single_ended();             // Display selected single ended channels
void print_channel_selection(uint8_t menu);

void menu_1_read_input();                             // Read channels
void menu_2_select_single_ended_differential();       // Sets LTC2308 to Single-Ended or Differential
void menu_3_select_uni_bipolar();                       // Sets LTC2308 to Bipolar or Unipolar
void menu_4_sleep();                                  

// Global variables
static uint8_t uni_bipolar = LTC2308_UNIPOLAR_MODE;    //!< Default set for unipolar mode
static uint8_t single_ended_differential = LTC2308_SINGLE_ENDED_MODE;    //!< LTC2308 Unipolar or Bipolar mode selection
static uint8_t LTC2308_bits = 12;                      //!< Resolution (12 bits)
static float LTC2308_vref = 4.096; 

// Constants
//! Lookup table to build the command for single-ended mode, input with respect to GND
const uint8_t BUILD_COMMAND_SINGLE_ENDED[8] = {LTC2308_CH0, LTC2308_CH1, LTC2308_CH2, LTC2308_CH3,
    LTC2308_CH4, LTC2308_CH5, LTC2308_CH6, LTC2308_CH7
                                              }; //!< Builds the command for single-ended mode, input with respect to GND

//! Lookup table to build the command for differential mode with the selected uni/bipolar mode
const uint8_t BUILD_COMMAND_DIFF[8] = {LTC2308_P0_N1, LTC2308_P2_N3, LTC2308_P4_N5, LTC2308_P6_N7,
                                       LTC2308_P1_N0, LTC2308_P3_N2, LTC2308_P5_N4, LTC2308_P7_N6
                                      }; //!< Build the command for differential mode


//! Initialize Linduino
void setup()
{
  uint16_t adc_code; 
  
  quikeval_SPI_init();           // Configure the spi port for 4MHz SCK
  quikeval_SPI_connect();        // Connect SPI to main data port
  Serial.begin(115200);          // Initialize the serial port to the PC
  print_title();
  print_prompt();
}


//! Repeats Linduino loop
void loop()
{
  uint16_t user_command;

  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:
          menu_1_read_input();
          break;
        case 2:
          menu_2_select_single_ended_differential();
          break;
        case 3:
          menu_3_select_uni_bipolar();
          break;
        case 4:
          menu_4_sleep();
          break;
        default:
          Serial.println(F("Invalid Option"));
          break;
      }
      Serial.println();
      Serial.println(F("*************************"));
      print_prompt();
  }
}


// Function Definitions
//! Read channels
void menu_1_read_input()
{
  uint8_t user_command;
  uint16_t adc_command;         // The LTC2308 command byte    
  uint16_t adc_code = 0;    // The LTC2308 code
  uint16_t display_code;
  uint8_t x, y, startcount, endcount;
  float adc_voltage;
  
  if (uni_bipolar == LTC2308_UNIPOLAR_MODE)
  {
    if (single_ended_differential == LTC2308_SINGLE_ENDED_MODE)
    {
    Serial.println(F("  Read Input in Single-Ended, Unipolar mode:"));
    Serial.println(F("  Note that in Unipolar mode, input voltages less than zero are reported as 0.0V"));
    user_command = print_user_command_single_ended();
    }
    else
    {
    Serial.println(F("  Read Input in Differential, Unipolar mode:"));
    Serial.println(F("  Note that in Unipolar mode, input voltages less than zero are reported as 0.0V"));
    user_command = print_user_command_differential();
    }    
  }
  else
  {
    if (single_ended_differential == LTC2308_SINGLE_ENDED_MODE)
    {
    Serial.println(F("  Read Input in Single-Ended, Bipolar mode:"));
    user_command = print_user_command_single_ended();
    }
    else
    {
    Serial.println(F("  Read Input in Differential, Bipolar mode:"));
    user_command = print_user_command_differential();
    }    
  }

  if (user_command == 8)  //read all channels
  {
    startcount = 0;
    endcount = 7;
  }
  else 
  {
    startcount = user_command;
    endcount = user_command;
  }
        
  if(single_ended_differential == LTC2308_SINGLE_ENDED_MODE)  //read single-ended
  {
    adc_command = BUILD_COMMAND_SINGLE_ENDED[0] | uni_bipolar;
    LTC2308_read(LTC2308_CS, adc_command, &adc_code);     // Throws out last reading and starts CH0 conversion
    for (x = startcount; x <= endcount; x++)
    {
            adc_command = BUILD_COMMAND_SINGLE_ENDED[x % 8] | uni_bipolar; // Send channel config for the NEXT conversion to take place
            LTC2308_read(LTC2308_CS, adc_command, &adc_code);     // Throws out last reading and starts CH0 conversion
            LTC2308_read(LTC2308_CS, adc_command, &adc_code);     // Throws out last reading and starts CH0 conversion

            display_code = adc_code >> (16 - LTC2308_bits);
            display_code = display_code & 0xFFF;

            Serial.print(F("  Received Code: b"));
            Serial.println(display_code, BIN);
            
            adc_voltage = LTC2308_code_to_voltage(adc_code, LTC2308_vref, uni_bipolar);
            Serial.print(F("  Voltage read on "));
            Serial.print(F("Ch"));
            Serial.print(x);
            Serial.print(F(": "));
            Serial.print(adc_voltage, 4);
            Serial.println(F("V"));
            Serial.println();
    }
  }

  else  //read differential
  {
    adc_command = BUILD_COMMAND_SINGLE_ENDED[0] | uni_bipolar;
    LTC2308_read(LTC2308_CS, adc_command, &adc_code);     // Throws out last reading and starts CH0 conversion
    for (x = startcount; x <= endcount; x++)
    {
          adc_command = BUILD_COMMAND_DIFF[x % 8] | uni_bipolar; // Send channel config for the NEXT conversion to take place
          LTC2308_read(LTC2308_CS, adc_command, &adc_code);     // Throws out last reading and starts CH0 conversion
          LTC2308_read(LTC2308_CS, adc_command, &adc_code);   // Read previous channel conversion (x-1) and start next one (x)
    
          display_code = adc_code >> (16 - LTC2308_bits);
          display_code = display_code & 0xFFF;

          Serial.print(F("  Received Code: b"));
          Serial.println(display_code, BIN);

          adc_voltage = LTC2308_code_to_voltage(adc_code, LTC2308_vref, uni_bipolar);
          Serial.print(F("  Voltage read between Chs "));
          print_channel_selection(x + y);
          Serial.print(adc_voltage, 4);
          Serial.println(F("V"));
          Serial.println();
    }
  }
}


//! Sets LTC2308 to Single-Ended or Differential
void menu_2_select_single_ended_differential()
{
  uint8_t user_command;

  Serial.println(F("\n  0 = Single-Ended"));
  Serial.println(F("  1 = Differential"));
  Serial.print(F("  Enter a Command: "));

  user_command = read_int();    // Read user input for uni_bipolar 
  Serial.println(user_command);
  switch (user_command)
      {
        case 0:
          Serial.println(F("  Single-Ended mode selected"));
          single_ended_differential = LTC2308_SINGLE_ENDED_MODE;
        break;
        case 1:
          Serial.println(F("  Differential mode selected"));
          single_ended_differential = LTC2308_DIFFERENTIAL_MODE;
          break; 
        default:
        {
          Serial.println("  Invalid Option");
          return;
        }
          break;
      }    
}


//! Select unipolar (0-REFCOMP) or bipolar (+/- 0.5 x REFCOMP) mode
//! @return void
void menu_3_select_uni_bipolar()
{
  uint8_t user_command;

  Serial.println(F("\n  0 = Bipolar"));
  Serial.println(F("  1 = Unipolar"));
  Serial.print(F("  Enter a Command: "));

  user_command = read_int();    // Read user input for uni_bipolar 
  Serial.println(user_command);
  switch (user_command)
      {
        case 0:
          Serial.println(F("  Bipolar mode selected"));
          uni_bipolar = LTC2308_BIPOLAR_MODE;
        break;
        case 1:
          Serial.println(F("  Unipolar mode selected"));
          uni_bipolar = LTC2308_UNIPOLAR_MODE;
          break; 
        default:
          Serial.println("  Invalid Option");
          return;
          break;
      }    
}


//! Put LTC2308 to sleep (low power)
//! @return void
void menu_4_sleep()
{
  // Sleep Mode
  uint16_t user_command;
  uint16_t adc_code = 0;                                        // The LTC2308 code
  LTC2308_read(LTC2308_CS, LTC2308_SLEEP_MODE, &adc_code);      // Build ADC command for sleep mode
  Serial.println();
  Serial.print(F("  ADC Command: B"));
  Serial.println(LTC2308_SLEEP_MODE, BIN);
  Serial.println(F("  LTC2308 Is Now In Sleep Mode"));
  Serial.println(F("  Enter RETURN to exit Sleep Mode"));
  user_command = read_int();
  LTC2308_read(LTC2308_CS, LTC2308_NORMAL_MODE, &adc_code); // Exit Sleep Mode
}//! Prints the title block when program first starts.
void print_title()
{
  Serial.println();
  Serial.println(F("*****************************************************************"));
  Serial.println(F("* DC1186A Demonstration Program                                 *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* This program demonstrates how to send data and receive data   *"));
  Serial.println(F("* from the LTC2308 12-bit ADC.                                  *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* Set the baud rate to 115200 and select the newline terminator.*"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("*****************************************************************"));
}


//! Prints main menu.
void print_prompt()
{
  Serial.println(F("1-Read ADC Input "));
  Serial.println(F("2-Select Single-Ended / Differential measurement (default is Single_Ended)"));
  Serial.println(F("3-Select Unipolar / Bipolar measurement (default is Unipolar)"));
  Serial.println(F("4-Select Sleep Mode"));
  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.
uint8_t print_user_command_differential()
{
  uint8_t user_command;

  Serial.println(F("  *************************"));
  Serial.println(F("  0 = 0P-1N"));
  Serial.println(F("  1 = 2P-3N"));
  Serial.println(F("  2 = 4P-5N"));
  Serial.println(F("  3 = 6P-7N"));
  Serial.println(F("  4 = 1P-0N"));
  Serial.println(F("  5 = 3P-2N"));
  Serial.println(F("  6 = 5P_4N"));
  Serial.println(F("  7 = 7P = 6N"));
  Serial.println(F("  8 = ALL Even_P-Odd_N"));
  Serial.println(F("  m = Main Menu"));
  Serial.println();
  Serial.print(F("  Enter a Command: "));
    
  user_command = read_int();  // Read the menu command    
  Serial.println(user_command);
  if (user_command == 'm')
    return(0);
    
  switch (user_command)  //check for invalid selection
  {
    case 0:
      Serial.println(F("  0P-1N selected"));
      break;
    case 1:
      Serial.println(F("  2P-3N selected"));
      break;
    case 2:
      Serial.println(F("  4P-5N selected"));
      break;
    case 3:
      Serial.println(F("  6P-7N selected"));
      break;
    case 4:
      Serial.println(F("  1P-0N selected"));
      break;
    case 5:
      Serial.println(F("  3P-2N selected"));
      break;
    case 6:
      Serial.println(F("  5P-4N selected"));
      break;
    case 7:
      Serial.println(F("  7P-6N selected"));
      break;
    case 8:
      Serial.println(F("  ALL Even_P-Odd_N selected"));
      break;
    default:
      Serial.println(F("  Invalid Option"));
      break;
   }
  return(user_command);
}


//! Display selected differential channels. Displaying single-ended channels is
//! straightforward; not so with differential because the inputs can take either polarity.
void print_channel_selection(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(" 1P-0N:"));
      break;
    case 5:
      Serial.print(F(" 3P-2N:"));
      break;
    case 6:
      Serial.print(F(" 5P-4N:"));
      break;
    case 7:
      Serial.print(F(" 7P-6N:"));
      break;
  }
}


//! Display selected single-ended channel.
uint8_t print_user_command_single_ended()
{
  uint8_t user_command;
  Serial.println(F("  *************************"));                         
    Serial.println(F("  0 = CH0"));
    Serial.println(F("  1 = CH1"));
    Serial.println(F("  2 = CH2"));
    Serial.println(F("  3 = CH3"));
    Serial.println(F("  4 = CH4"));
    Serial.println(F("  5 = CH5"));
    Serial.println(F("  6 = CH6"));
    Serial.println(F("  7 = CH7"));
    Serial.println(F("  8 = ALL"));
    Serial.println(F("  m = Main Menu"));
    Serial.println();
    Serial.print(F("  Enter a Command: "));

    user_command = read_int();  // Read the single-ended menu command
    Serial.println(user_command);
    if (user_command == 'm')
      return(0);
      
  switch (user_command)  //check for invalid selection
  {
    case 0:
      Serial.println(F("  CH0 selected"));
      break;
    case 1:
      Serial.println(F("  CH1 selected"));
      break;
    case 2:
      Serial.println(F("  CH2 selected"));
      break;
    case 3:
      Serial.println(F("  CH3 selected"));
      break;
    case 4:
      Serial.println(F("  CH4 selected"));
      break;
    case 5:
      Serial.println(F("  CH5 selected"));
      break;
    case 6:
      Serial.println(F("  CH6 selected"));
      break;
    case 7:
      Serial.println(F("  CH7 selected"));
      break;
    case 8:
      Serial.println(F("  All selected"));
      break;
    default:
      Serial.println(F("  Invalid Option"));
      break;
   }

  return(user_command);
}

/*!
LTC2308: 16-bit 8-channel 100ksps ADC

@verbatim

The LTC2308 is an 8-channel 12-bit A/D converter with 
with serial I/O, and an internal reference. The ADCs typically draw only 1.3mA 
from a single 5V supply. The 8-channel input multiplexer can be configured for 
either single-ended or differential inputs and unipolar or bipolar conversions 
(or combinations thereof). The automatic nap and sleep modes benefit power 
sensitive applications. 

The LTC2308's DC performance is outstanding with a +/-2LSB INL specification and 
no missing codes over temperature. The signal-to-noise ratio (SNR) for the 
LTC2308 is typically 89dB, with the internal reference. 

SPI DATA FORMAT (MSB First):

            Byte #1                           Byte #2
Data Out :  D15 D14 D13 D12 D11 D10  D9  D8    D7  D6  D5  D4  D3  D2  D1  D0
Data In  :  SD  OS  S1  S0  UNI GAIN NAP SLP   X   X   X   X   X   X   X   X

SD   : Single/Differential Bit
OS   : ODD/Sign Bit
Sx   : Address Select Bit
UNI  : Unipolar/Bipolar Bit
GAIN : Input Span Bit
NAP  : Nap Mode Bit
SLP  : Sleep Mode Bit
Dx   : Data Bits
X    : Don't care


Example Code:

Read Channel 0 in Single-Ended Unipolar mode when input is with respect to GND

    adc_command = LTC2308_CH0 | LTC2308_UNIPOLAR_MODE | LTC2308_LOW_GAIN_MODE | LTC2308_NORMAL_MODE;     // Single-ended, CH0, unipolar, low gain, normal mode.
    LTC2308_read(LTC2308_CS, adc_command, &adc_code);   // Throws out last reading
    LTC2308_read(LTC2308_CS, adc_command, &adc_code);   // Obtains the current reading and stores to adc_code variable

    // Convert adc_code to voltage
    adc_voltage = LTC2308_unipolar_code_to_voltage(adc_code, LTC2308_lsb, LTC2308_offset_unipolar_code);

@endverbatim

http://www.linear.com/product/LTC2308

http://www.linear.com/product/LTC2308#demoboards

REVISION HISTORY
$Revision: 3018 $
$Date: 2014-12-01 15:53:20 -0800 (Mon, 01 Dec 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 LTC2308
    Header for LTC2308: 16-bit 8-channel 100ksps ADC
*/

#ifndef LTC2308_H
#define LTC2308_H

#include <SPI.h>

//! Define the SPI CS pin
#ifndef LTC2308_CS
#define LTC2308_CS QUIKEVAL_CS
#endif

//! @name LTC2308 Single-Ended Channel Addresses
//! @{
// Single-Ended Channel Address
#define LTC2308_CH0             0x80
#define LTC2308_CH1             0xC0
#define LTC2308_CH2             0x90
#define LTC2308_CH3             0xD0
#define LTC2308_CH4             0xA0
#define LTC2308_CH5             0xE0
#define LTC2308_CH6             0xB0
#define LTC2308_CH7             0xF0
//!@}

//! @name LTC2308 Differential Channel Addresses
//! @{
// Differential Channel Address
#define LTC2308_P0_N1           0x00
#define LTC2308_P1_N0           0x40

#define LTC2308_P2_N3           0x10
#define LTC2308_P3_N2           0x50

#define LTC2308_P4_N5           0x20
#define LTC2308_P5_N4           0x60

#define LTC2308_P6_N7           0x30
#define LTC2308_P7_N6           0x70
//!@}

//! @name LTC2308 Uni/GAIN config bits
//! @{
// Unipolar Mode Command
#define LTC2308_UNIPOLAR_MODE   0x08
#define LTC2308_BIPOLAR_MODE    0x00
// Single-Ended Mode Command
#define LTC2308_SINGLE_ENDED_MODE   0x80
#define LTC2308_DIFFERENTIAL_MODE  0x00
//!@}

//! @name LTC2308 Sleep/Nap config bits
//! @{
// Sleep Mode Command
#define LTC2308_SLEEP_MODE      0x01
#define LTC2308_NORMAL_MODE     0x00
// Nap Mode Command
#define LTC2308_NAP_MODE   	  0x02
//!@}

/*
  Example command
  adc_command = LTC2308_CH0 | LTC2308_UNIPOLAR_MODE | LTC2308_LOW_GAIN_MODE | LTC2308_NORMAL_MODE;     // Single-ended, CH0, unipolar, low gain, normal mode.
 */


//! Reads the ADC and returns 16-bit data
//! @return void
void LTC2308_read(uint8_t cs,           //!< Chip Select Pin 
                  uint8_t adc_command,  //!< Channel address, config bits ORed together
                  uint16_t *adc_code    //!< Returns code read from ADC (from previous conversion)
                 );


//! Calculates the LTC2308 input's unipolar voltage given the binary data and lsb weight.
//! @return Floating point voltage
float LTC2308_code_to_voltage(uint16_t adc_code,                  //!< Raw ADC code
                              float vref,			//!<
							  uint8_t uni_bipolar        //!<
                              );

#endif  //  LTC2308_H

/*!
LTC2308: 12-Bit 8-Channel 200ksps ADC

@verbatim

The LTC2308 is an 8-channel 12-bit A/D converter with 
serial I/O, and an internal reference. The ADCs typically draw only 1.3mA from a 
single 5V supply. The 8-channel input multiplexer can be configured for either 
single-ended or differential inputs and unipolar or bipolar conversions (or 
combinations thereof). The automatic nap and sleep modes benefit power sensitive 
applications. 

The LTC2308's DC performance is outstanding with a +/-2LSB INL specification and 
no missing codes over temperature. The signal-to-noise ratio (SNR) for the 
LTC2308 is typically 89dB, with the internal reference. 

@endverbatim

http://www.linear.com/product/LTC2308

http://www.linear.com/product/LTC2308#demoboards

REVISION HISTORY
$Revision: 3018 $
$Date: 2014-12-01 15:53:20 -0800 (Mon, 01 Dec 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 LTC2308 LTC2308: 12-Bit 8-Channel 200ksps ADC

/*! @file
    @ingroup LTC2308
    Library for LTC2308: 12-Bit 8-Channel 200ksps ADC
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "LTC2308.h"
#include <SPI.h>


// Reads the ADC  and returns 16-bit data
void LTC2308_read(uint8_t cs, uint8_t adc_command, uint16_t *adc_code)
{
  spi_transfer_word(cs, (uint16_t)(adc_command<<8), adc_code);
}


// Calculates the LTC2308 input voltage given the data, range, and unipolar/bipolar status.
float LTC2308_code_to_voltage(uint16_t adc_code, float vref, uint8_t uni_bipolar)
{
  float voltage;
  float sign = 1;

  if(uni_bipolar == LTC2308_UNIPOLAR_MODE)
  {
  	voltage = (float)adc_code;
 	voltage = voltage / (pow(2,16)-1);    //! 2) This calculates the input as a fraction of the reference voltage (dimensionless)
  }
  else
  {
	vref = vref/2;
	if ((adc_code & 0x8000) == 0x8000)	//adc code is < 0
  	{
    	  adc_code = (adc_code ^ 0xFFFF)+1;                                    //! Convert ADC code from two's complement to binary
    	  sign = -1;
	}
  	voltage = sign*(float)adc_code;
	voltage = voltage / (pow(2,15)-1);    //! 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);
}