LTC2378-16 - 16-Bit, 1Msps, Low Power SAR ADC with 97dB SNR

/*!
Linear Technology DC1925A Demonstration Board with SPI interface.
LTC2376-20: 20-Bit, 250Ksps ADC
LTC2377-20: 20-Bit, 500Ksps ADC
LTC2378-20: 20-Bit, 1Msps ADC
Max SCK rate is 100MHz.

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator.
   Equipment required is a precision voltage source (null box) and a precision voltmeter (to monitor voltage source).
   No external power supply is required.
   Ensure JP1 is installed in the default position from the factory.

  How to test:
   The voltage source should be connected with positive and negative leads to the positive & negative ADC inputs. Ensure the differential voltage is within the
   range of -VREF to +VREF. 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/LTC2376-20
http://www.linear.com/product/LTC2377-20
http://www.linear.com/product/LTC2378-20

http://www.linear.com/product/LTC2376-20#demoboards
http://www.linear.com/product/LTC2377-20#demoboards
http://www.linear.com/product/LTC2378-20#demoboards

REVISION HISTORY
$Revision: 1792 $
$Date: 2013-08-9 13:58:53 -0700 (Thu, 25 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.
*/

/*! @file
    @ingroup LTC2378
*/

#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 "LTC2378.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 menu_1_read_input();
void menu_2_select_gain_compression();

// Global variables
static uint8_t LTC2378_dgc = 0;         //!< Default set for no gain compression
static uint8_t LTC2378_bits = 20;                   //!< Default set for 20 bits
float LTC2378_vref = 5;


//! Initialize Linduino
void setup()
{
//  quikeval_I2C_init();           // Configure the EEPROM I2C port for 100kHz
  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())
    {
      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:
          menu_1_read_input();
          break;
        case 2:
          menu_2_select_gain_compression();
          break;
        default:
          Serial.println("  Invalid Option");
          break;
      }
      Serial.println();
      print_prompt();
    }
  }
}


// Function Definitions
//! Read channel
//! @return void
void menu_1_read_input()
{
  uint8_t user_command;
  int32_t adc_code;                           // The LTC2378 code
  int32_t display_code;
  float adc_voltage; 
    
    // Read and display a selected channel
    LTC2378_read(LTC2378_CS, &adc_code);  //discard first reading
    delay(100);
    LTC2378_read(LTC2378_CS, &adc_code);
  
    display_code = adc_code >> (32 - LTC2378_bits);  //shift to the right
    display_code = display_code & 0xFFFFF;  //mask off 20 bits        
  
    Serial.print(F("  Received Code: b"));
    Serial.println(display_code, BIN);
 
    adc_voltage = LTC2378_code_to_voltage(adc_code, LTC2378_dgc, LTC2378_vref);    // Convert the received code to voltage  
         
    Serial.print(F("  Equivalent voltage: "));
    Serial.print(adc_voltage, 4);
    Serial.println(F("V")); 
}
  
  
//! Select gain compression
//! @return void
void menu_2_select_gain_compression()
{
  uint8_t user_command;
    
  Serial.println(F("  0 = No Gain Compression"));
  Serial.println(F("  1 = Gain Compression"));
  Serial.print(F("  Enter a Command, based upon the position of jumper JP6: "));

  user_command = read_int();    // Read user input
  Serial.println(user_command);   // Prints the user command to com port
  switch (user_command)
    {
        case 0:
          Serial.println(F("  No Gain compression"));
          LTC2378_dgc = 0;
          break;
        case 1:
          Serial.println(F("  Gain compression"));
          LTC2378_dgc = 1;
          break;
        default:
        {
          Serial.println("  Invalid Option");
          return;
        }
          break;
    }
}


//! Prints the title block when program first starts.
void print_title()
{
  Serial.println();
  Serial.println(F("*****************************************************************"));
  Serial.println(F("* DC1925A Demonstration Program                                 *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* This program demonstrates how to receive data                 *"));
  Serial.println(F("* from the following ADCs:                                      *"));
  Serial.println(F("*   LTC2376-20                                                  *"));
  Serial.println(F("*   LTC2377-20                                                  *"));
  Serial.println(F("*   LTC2378-20                                                  *"));
  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("*************************"));
  Serial.println(F("1-Read ADC Input"));
  Serial.println(F("2-Select No Gain Compression / Gain Compression (default is no compression)"));
  Serial.print(F("Enter a command:"));
}

/*!
LTC2376-20: 20-Bit, 250Ksps ADC
LTC2377-20: 20-Bit, 500Ksps ADC
LTC2378-20: 20-Bit, 1Msps ADC

@verbatim

The following parts (DUT) are pin-compatible, 20-bit A/D converters with serial I/O, and an internal reference:
LTC2376-20: 20-Bit, 250Ksps ADC
LTC2377-20: 20-Bit, 500Ksps ADC
LTC2378-20: 20-Bit, 1Msps ADC

The DUTs typically draw only 8.4 mA from a single 2.5V supply. The automatic nap and sleep modes benefit power sensitive applications. 

The DUTs DC performance is outstanding with a +/-0.5 ppm INL specification and 
no missing codes over temperature. The signal-to-noise ratio (SNR) for the LTC2378 is typically 104 dB, with the internal reference.  

@endverbatim

http://www.linear.com/product/LTC2376-20
http://www.linear.com/product/LTC2377-20
http://www.linear.com/product/LTC2378-20

http://www.linear.com/product/LTC2376-20#demoboards
http://www.linear.com/product/LTC2377-20#demoboards
http://www.linear.com/product/LTC2378-20#demoboards

REVISION HISTORY
$Revision: 1785 $
$Date: 2013-07-25 08:47:24 -0700 (Thu, 25 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 LTC2378 LTC2378: 16/18/20-Bit 1Msps ADC

/*! @file
    @ingroup LTC2378
    Library for LTC2378: 16/18/20-Bit 1Msps ADC
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "LTC2378.h"
#include <SPI.h>


// Reads from a SPI LTC2378-XX device that has no configuration word and a 32 bit output word in 2's complement format.
void LTC2378_read(uint8_t cs, int32_t *ptr_adc_code)
{
  LT_union_int16_2bytes command;  	// LTC2378 data and command
  command.LT_uint16 = 0;                // Set to zero, not necessary but avoids
                                        // random data in scope shots.

//Form a four byte object to hold four bytes of data
  LT_union_int32_4bytes data;	//instantiate the union
  data.LT_byte[3] = 0; 
  data.LT_byte[2] = 0; 
  data.LT_byte[1] = 0; 
  data.LT_byte[0] = 0; 

  spi_transfer_block(cs,command.LT_byte,data.LT_byte,4);

  *ptr_adc_code = data.LT_int32;
 
  return;
}


// Calculates the voltage corresponding to an adc code in 2's complement, given the reference voltage (in volts)
float LTC2378_code_to_voltage(int32_t adc_code, uint8_t gain_compression, float vref)
{
  float voltage;

  if(gain_compression == 1)
	  vref = 0.8*vref;

  voltage = (float)adc_code;
  voltage = voltage / (pow(2,31)-1);    //! 2) This calculates the input as a fraction of the reference voltage (dimensionless)
  voltage = voltage * vref + 0.1;           //! 3) Multiply fraction by Vref to get the actual voltage at the input (in volts)

  return(voltage);
}

/*!
LTC2376-20: 20-Bit, 250Ksps ADC
LTC2377-20: 20-Bit, 500Ksps ADC
LTC2378-20: 20-Bit, 1Msps ADC

@verbatim

The following parts (DUT) are pin-compatible, 20-bit A/D converters with serial I/O, and an internal reference:
LTC2376-20: 20-Bit, 250Ksps ADC
LTC2377-20: 20-Bit, 500Ksps ADC
LTC2378-20: 20-Bit, 1Msps ADC

The DUTs typically draw only 8.4 mA from a single 2.5V supply. The automatic nap and sleep modes benefit power sensitive applications. 

The DUTs DC performance is outstanding with a +/-0.5 ppm INL specification and 
no missing codes over temperature. The signal-to-noise ratio (SNR) for the LTC2378 is typically 104 dB, with the internal reference.  

Example Code:

Read ADC input.

    LTC2378_read(LTC2378_CS, &adc_code);   // Throws out last reading
    LTC2378_read(LTC2378_CS, &adc_code);   // Obtains the current reading and stores to adc_code variable

    // Convert adc_code to voltage
    adc_voltage = LTC2378_code_to_voltage(adc_code, vref);

@endverbatim

http://www.linear.com/product/LTC2376-20
http://www.linear.com/product/LTC2377-20
http://www.linear.com/product/LTC2378-20

http://www.linear.com/product/LTC2376-20#demoboards
http://www.linear.com/product/LTC2377-20#demoboards
http://www.linear.com/product/LTC2378-20#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.
*/

/*! @file
    @ingroup LTC2378_
    Header for LTC2378: 16/18/20-bit 1Msps ADC
*/

#ifndef LTC2378_H
#define LTC2378_H

#include <SPI.h>

//! Define the SPI CS pin
#ifndef LTC2378_CS
#define LTC2378_CS QUIKEVAL_CS
#endif

//! @name LTC2378 Channel Address
//! @{
// Channel Address
#define LTC2378_ADDRESS             0x00
//!@}


//! Reads the LTC2378 and returns 32-bit data in 2's complement format
//! @return void
void LTC2378_read(uint8_t cs,           //!< Chip Select Pin 
                  int32_t *ptr_adc_code    //!< Returns code read from ADC (from previous conversion)
                 );


//! Calculates the LTC2378 input voltage given the binary data and lsb weight.
//! @return Floating point voltage
float LTC2378_code_to_voltage(int32_t adc_code,                   //!< Raw ADC code 
								uint8_t gain_compression,
								float vref							//!< Reference voltage
								);

#endif  //  LTC2378_H