LTC2302 - Low Noise, 500ksps, 1-/2-Channel, 12-Bit ADC

/*!
Linear Technology DC1186A Demonstration Board.
LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator. No
   external power supply is required and it has an on-board reference voltage
   of 4.096V. The analog input is given at IN+ and IN-.

   There are options to chose between unipolar and bipolar modes.

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

@endverbatim

http://www.linear.com/product/LTC2302

http://www.linear.com/product/LTC2302#demoboards

REVISION HISTORY
$Revision: 3237 $
$Date: 2015-03-05 17:45:18 -0800 (Thu, 05 Mar 2015) $

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 LTC2302
*/

// Headerfiles
#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 <SPI.h>
#include "LTC2302.h"

// Global variables
static uint16_t uni_bipolar = LTC2302_UNIPOLAR;    //!< Default set for unipolar mode
static float LTC2302_vref = 4.096;

//! 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())               // 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_uni_bipolar();
        break;
      default:
        Serial.println(F("Invalid Option"));
        break;
    }
    Serial.println();
    Serial.println(F("*************************\n"));
    print_prompt();
  }
}

//! Read ADC code and display the measured voltage
void menu_1_read_input()
{
  uint16_t adc_command;
  uint16_t adc_code;
  float voltage;

  adc_command = uni_bipolar;
  LTC2302_read(QUIKEVAL_CS, adc_command, &adc_code);
  adc_code = (adc_code >> 4) & 0x0FFF;
  voltage = LTC2302_code_to_voltage(adc_code, LTC2302_vref, uni_bipolar);
  Serial.print("\nMeasured Voltage = ");
  Serial.println(voltage);
}

//! Select unipolar (0-VREF) or bipolar (+/- 0.5 x VREF) mode
void menu_2_select_uni_bipolar()
{
  uint8_t user_command;

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

  user_command = read_int();    // Read user input for uni_bipolar
  Serial.println(user_command);
  switch (user_command)
  {
    case 0:
      Serial.println(F("\n  Bipolar mode selected"));
      uni_bipolar = LTC2302_BIPOLAR;
      break;
    case 1:
      Serial.println(F("\n  Unipolar mode selected"));
      uni_bipolar = LTC2302_UNIPOLAR;
      break;
    default:
      Serial.println("\n  Invalid Option");
      return;
      break;
  }
}

//! Prints the title block when program first starts.
void print_title()
{
  Serial.println();
  Serial.println(F("*****************************************************************"));
  Serial.println(F("* DC1339A Demonstration Program                                 *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* This program demonstrates how to send data and receive data   *"));
  Serial.println(F("* from the LTC2302 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("  OPTIONS\n"));
  Serial.println(F("1-Read ADC Input "));
  Serial.println(F("2-Select Unipolar / Bipolar measurement (default is Unipolar)"));
  Serial.println();
  Serial.print(F("Enter a command:  "));
}

/*!
LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.

@verbatim

The LTC2302 is a single-channel 12-bit A/D converter with with serial I/O.
The part can be configured to operate on unipolar or bipolar modes. The
automatic sleep mode benefits power sensitive applications.

SPI DATA FORMAT (MSB First):

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

OS   : ODD/Sign Bit
UNI  : Unipolar/Bipolar Bit
Dx   : Data Bits
X    : Don't care

@endverbatim

http://www.linear.com/product/LTC2302

http://www.linear.com/product/LTC2302#demoboards

REVISION HISTORY
$Revision: 3237 $
$Date: 2015-03-05 17:45:18 -0800 (Thu, 05 Mar 2015) $

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 LTC2302
    Header for LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.
*/

#ifndef LTC2302_H
#define LTC2302_H

//! Define the SPI CS pin
#ifndef LTC2302_CS
#define LTC2302_CS QUIKEVAL_CS
#endif

//! @name LTC2302 Uni/Bipolar Config bits
//! @{
// Unipolar Mode Command
#define LTC2302_UNIPOLAR   0xBFFF
// Bipolar Mode Command
#define LTC2302_BIPOLAR    0x0000
//!@}

//! Reads the ADC and returns 16-bit data
//! @return void
void LTC2302_read(uint8_t cs,                 //!< Chip Select Pin
                  uint16_t adc_command,       //!< Channel address, config bits ORed together
                  uint16_t *adc_code          //!< Returns code read from ADC (from previous conversion)
                 );

//! Calculates the LTC2302 input voltage given the data, range, and unipolar/bipolar status.
//! @return Floating point voltage
float LTC2302_code_to_voltage(uint16_t adc_code,  //!< Raw ADc code
                              float vref,       //!< Reference voltage
                              uint8_t uni_bipolar //!< Choice of unipolar/bipolar
                             );
#endif  //  LTC2302_H

/*!
LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.

@verbatim

The LTC2302 is a single-channel 12-bit A/D converter with with serial I/O.
The part can be configured to operate on unipolar or bipolar modes. The
automatic sleep mode benefits power sensitive applications.

SPI DATA FORMAT (MSB First):

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

OS   : ODD/Sign Bit
UNI  : Unipolar/Bipolar Bit
Dx   : Data Bits
X    : Don't care

@endverbatim

http://www.linear.com/product/LTC2302

http://www.linear.com/product/LTC2302#demoboards

REVISION HISTORY
$Revision: 3237 $
$Date: 2015-03-05 17:45:18 -0800 (Thu, 05 Mar 2015) $

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 LTC2302 LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.

/*! @file
    @ingroup LTC2302
    Library for LTC2302: 12-Bit, 1-Channel 500ksps SAR ADC with SPI Interface.
*/

#include "LT_SPI.h"
#include <SPI.h>
#include "LTC2302.h"

// Reads the ADC  and returns 16-bit data
void LTC2302_read(uint8_t cs, uint16_t adc_command, uint16_t *adc_code)
{
  spi_transfer_word(cs, (uint16_t)(adc_command), adc_code);
  spi_transfer_word(cs, (uint16_t)(adc_command), adc_code); // Throws out last reading and starts a new connection
}

// Calculates the LTC2302 input voltage given the data, range, and unipolar/bipolar status.
float LTC2302_code_to_voltage(uint16_t adc_code, float vref, uint8_t uni_bipolar)
{
  float voltage;
  float sign = 1;

  if (uni_bipolar == LTC2302_UNIPOLAR)
  {
    voltage = (float)adc_code;
    voltage = vref * voltage / (4095);          //! This calculates the actual voltage at the input (in volts)
  }
  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 = vref * voltage / 2047;           //! This calculates the actual voltage at the input (in volts)
  }

  return(voltage);
}