LTC2482 - 16-Bit ΔΣ ADC with Easy Drive Input Current Cancellation

/*!
Linear Technology DC941A Demonstration Board.
LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.

@verbatim

The LTC2480 is a 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.
The LTC2482 allows a wide common mode input range (0V to VCC) independent of the
reference voltage. The reference can be as low as 100mV or can be tied directly to
VCC. The noise level is 600nV RMS independent of VREF . This allows direct
digitization of low level signals with 16-bit accuracy. The LTC2482 includes an on-chip
trimmed oscillator, eliminating the need for external crystals or oscillators and
provides 87dB rejection of 50Hz and 60Hz line frequency noise. Absolute accuracy and low
drift are automatically maintained through continuous, transparent, offset and
full-scale calibration.

The voltage on the differential input pins can have any value between GND – 0.3V
and VCC + 0.3V. Within these limits the converter bipolar input range (VIN = IN+ – IN–)
extends from –0.5 • VREF to 0.5 • VREF. Outside this input range the converter
produces unique overrange and underrange output codes.

@endverbatim

http://www.linear.com/product/LTC2482

http://www.linear.com/product/LTC2482#demoboards

REVISION HISTORY
$Revision: 5670 $
$Date: 2016-09-02 10:55:41 -0700 (Fri, 02 Sep 2016) $

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 LTC2482
*/

#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 "LTC24XX_general.h"
#include "LTC2482.h"
#include <SPI.h>

// Function Declaration
void print_title();                             // Print the title block
void print_prompt();                            // Prompt the user for an input command

void menu_1_read_input();
void menu_2_reference_voltage();

static uint8_t demo_board_connected;            //!< Set to 1 if the board is connected

// Global variables
float LTC2482_vref = 5;
float LTC2482_range = LTC2482_vref/2;

//! Initialize Linduino
void setup()
{
  char demo_name[]="DC941";     // Demo Board Name stored in QuikEval EEPROM

  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();
  demo_board_connected = discover_demo_board(demo_name);
  if (demo_board_connected)
  {
    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_reference_voltage();
          break;
        default:
          Serial.println(F("Invalid Option"));
          break;
      }
      Serial.println();
      print_prompt();
    }
  }
}

// Function Definitions
//! Read channel
//! @return void
void menu_1_read_input()
{
  uint8_t user_command;
  uint32_t adc_code;                           // The LTC2482 code
  int32_t display_code = 0;
  float adc_voltage;                               // The LTC2482 voltage

  // Read and display
  LTC2482_read(LTC2482_CS, &adc_code);
  delay(200);
  LTC2482_read(LTC2482_CS, &adc_code);

  display_code = adc_code >> 4;
  display_code = display_code & 0xFFFF;

  Serial.print(F("  Received Code: 0x"));
  Serial.println(display_code, HEX);

  // Convert the received code to voltage
  adc_voltage = LTC2482_code_to_voltage(display_code, LTC2482_range);

  if (adc_code & 0x100000)    // Checking sign bit
  {
    adc_voltage = LTC2482_range - adc_voltage;
    adc_voltage = adc_voltage * (-1);
  }

  Serial.print(F("  Equivalent voltage: "));
  Serial.print(adc_voltage, 4);
  Serial.println(F(" V"));
}

void menu_2_reference_voltage()
{
  Serial.print(F("\n  Enter the reference voltage: "));
  LTC2482_vref = read_float();
  Serial.print(LTC2482_vref);
  Serial.println(F(" V"));

  LTC2482_range = LTC2482_vref/2;
}

//! Prints the title block when program first starts.
void print_title()
{
  Serial.print(F("\n*****************************************************************\n"));
  Serial.print(F("* DC941A 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 Input\n"));
  Serial.print(F("2-Change reference voltage\n"));
  Serial.print(F("\nEnter a Command: "));
}

/*!
LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.

@verbatim

The LTC2480 is a 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.
The LTC2482 allows a wide common mode input range (0V to VCC) independent of the
reference voltage. The reference can be as low as 100mV or can be tied directly to
VCC. The noise level is 600nV RMS independent of VREF . This allows direct
digitization of low level signals with 16-bit accuracy. The LTC2482 includes an on-chip
trimmed oscillator, eliminating the need for external crystals or oscillators and
provides 87dB rejection of 50Hz and 60Hz line frequency noise. Absolute accuracy and low
drift are automatically maintained through continuous, transparent, offset and
full-scale calibration.

@endverbatim

http://www.linear.com/product/LTC2482

http://www.linear.com/product/LTC2482#demoboards

REVISION HISTORY
$Revision: 5670 $
$Date: 2016-09-02 10:55:41 -0700 (Fri, 02 Sep 2016) $

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 LTC2482 LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.

/*! @file
    @ingroup LTC2482
    Library for LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.
*/

#include <stdint.h>
#include "Linduino.h"
#include "LT_SPI.h"

// Reads the LTC2482 and returns 24-bit data
void LTC2482_read(uint8_t cs, uint32_t *ptr_adc_code)
{
  LT_union_int32_4bytes data, command;  // LTC24XX data and command
  command.LT_uint32 = 0;
  data.LT_uint32 = 0;

  spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)3);

  *ptr_adc_code = data.LT_uint32;
}

// Calculates the LTC2482 input voltage given the binary data, reference voltage and input gain.
float LTC2482_code_to_voltage(uint32_t adc_code, float vref)
{
  float voltage;

  voltage = (float)adc_code;
  voltage = voltage / (pow(2,16)-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);
}

/*!
LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.

@verbatim

The LTC2480 is a 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.
The LTC2482 allows a wide common mode input range (0V to VCC) independent of the
reference voltage. The reference can be as low as 100mV or can be tied directly to
VCC. The noise level is 600nV RMS independent of VREF . This allows direct
digitization of low level signals with 16-bit accuracy. The LTC2482 includes an on-chip
trimmed oscillator, eliminating the need for external crystals or oscillators and
provides 87dB rejection of 50Hz and 60Hz line frequency noise. Absolute accuracy and low
drift are automatically maintained through continuous, transparent, offset and
full-scale calibration.

Example Code:

Read ADC input.

    LTC2482_read(LTC2482_CS, &adc_code);   // Throws out last reading
    LTC2482_read(LTC2482_CS, &adc_code);   // Obtains the current reading and stores to adc_code variable

  display_code = adc_code >> 4;
    display_code = display_code & 0xFFFF;

    // Convert adc_code to voltage
    adc_voltage = LTC2482_code_to_voltage(display_code, vref);

@endverbatim

http://www.linear.com/product/LTC2482

http://www.linear.com/product/LTC2482#demoboards

REVISION HISTORY
$Revision: 5670 $
$Date: 2016-09-02 10:55:41 -0700 (Fri, 02 Sep 2016) $

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 LTC2482
    Header for LTC2482: 16-Bit Delta-Sigma ADC with Easy Drive Input Current Cancellation.
*/

#ifndef LTC2482_H
#define LTC2482_H

//! Define the SPI CS pin
#ifndef LTC2482_CS
#define LTC2482_CS QUIKEVAL_CS
#endif

//! Reads the LTC2482 and returns 24-bit data
//! @return void
void LTC2482_read(uint8_t cs,         //!< Chip Select Pin
                  uint32_t *ptr_adc_code  //!< Returns code read from ADC (from previous conversion)
                 );

//! Calculates the LTC2482 input voltage given the binary data, reference voltage and input gain.
//! @return Floating point voltage
float LTC2482_code_to_voltage(uint32_t adc_code,      //!< Raw ADC code
                              float vref          //!< Reference voltage
                             );


#endif  //  LTC2482_H