LTC2636 - Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference

/*!
Linear Technology DC1466 Demonstration Board.
LTC2636: Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.

Linear Technology DC1488 Demonstration Board.
LTC2634: Quad 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.

@verbatim
NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator.
   The program displays calculated voltages which are based on the voltage
   of the reference used, be it internal or external. A precision voltmeter
   is needed to verify the actual measured voltages against the calculated
   voltage displayed. If an external reference is used, a precision voltage
   source is required to apply the external reference voltage. A
   precision voltmeter is also required to measure the external reference
   voltage. No external power supply is required. Any assembly option
   may be used: DC1466A-A, DC1466A-B, DC1466A-C, DC1466A-D.


  Explanation of Commands:
   1- Select DAC: Select one of four DACs to test : A, B, C, D.

   2- Write to DAC input register: Value is stored in the DAC for updating
      later, allowing multiple channels to be updated at once, either
      through a software "Update All" command or by asserting the LDAC# pin.
      User will be prompted to enter either a code in hex or decimal, or a
      voltage. If a voltage is entered, a code will be calculated based on
      the active scaling and reference parameters - ideal values if no
      calibration was ever stored.

   3- Write and Update: Similar to item 1, but DAC is updated immediately.

   4- Update DAC: Copies the value from the input register into the DAC
      Register. Note that a "write and update" command writes the code to
      BOTH the input register and DAC register, so subsequent "update"
      commands will simply re-copy the same data (no change in output.)

   5- Power Down DAC: Disable DAC output. Power supply current is reduced.
      DAC code present in DAC registers at time of shutdown are preserved.

   6- Set reference mode, either internal or external: Selecting external
      mode prompts for the external reference voltage, which is used directly
      if no individual DAC calibration is stored. The selection and entered
      voltage are stored to EEPROM so it is persistent across reset / power cycles.

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

@endverbatim

http://www.linear.com/product/LTC2636
http://www.linear.com/product/LTC2634

http://www.linear.com/product/LTC2636#demoboards
http://www.linear.com/product/LTC2634#demoboards

REVISION HISTORY
$Revision: 5074 $
$Date: 2016-05-09 16:57:13 -0700 (Mon, 09 May 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 LTC2636
*/

#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 "LTC2636.h"
#include <SPI.h>
#include <Wire.h>

// DAC Reference State
// Could have been zero or 1, this allows you to use the
// variable "reference_mode" as the command argument to a write
#define REF_INTERNAL LTC2636_CMD_INTERNAL_REFERENCE   //!< Stored reference state is Internal
#define REF_EXTERNAL LTC2636_CMD_EXTERNAL_REFERENCE   //!< Stored reference state is External

// Function Declaration
void restore_calibration();               // Read the DAC calibration from EEPROM, Return 1 if successful, 0 if not
void print_title();                         // Print the title block
void print_prompt(int16_t selected_dac);    // Prompt the user for an input command
int16_t prompt_voltage_or_code();
uint16_t get_voltage(float LTC2636_lsb, int16_t LTC2636_offset);
uint16_t get_code();

void menu_1_select_dac(int16_t *selected_dac);
void menu_2_write_to_input_register(int16_t selected_dac);
void menu_3_write_and_update_dac(int16_t selected_dac);
void menu_4_update_power_up_dac(int16_t selected_dac);
void menu_5_power_down_dac(int16_t selected_dac);
void menu_6_set_reference_mode();         // Int, ext, if ext, prompt for voltage
int8_t menu_7_calibrate_dacs();

// Global variables
static uint8_t demo_board_connected;   //!< Set to 1 if the board is connected
static uint8_t shift_count;        //!< The data align shift count. For 12-bits=4, 10-bits=6, 8-bits=8
static uint8_t reference_mode;         //!< Tells whether to set internal or external reference
static float reference_voltage;    //!< Reference voltage, either internal or external
static int16_t LTC2636_offset[9];      //!< DAC offset - index 8 for "all DACs"
static float LTC2636_lsb[9];           //!< The LTC2636 lsb - index 8 for "all DACs"
static uint8_t num_of_channels = 8;     // Change to 4 for LTC2634.

// Constants
//! Lookup table for DAC address. Allows the "All DACs" address to be indexed right after DAC D in loops.
//! This technique is very useful for devices with non-monotonic channel addresses.
const uint8_t address_map[9] = {LTC2636_DAC_A, LTC2636_DAC_B, LTC2636_DAC_C, LTC2636_DAC_D, LTC2636_DAC_E, LTC2636_DAC_F, LTC2636_DAC_G, LTC2636_DAC_H, LTC2636_DAC_ALL};  //!< Map entered option 0..2 to DAC address

//! Used to keep track to print voltage or print code
enum
{
  PROMPT_VOLTAGE = 0, /**< 0 */
  PROMPT_CODE = 1     /**< 1 */
};

//! Initialize Linduino
void setup()
// Setup the program
{
  char demo_name[] = "DC1466";  // 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)
  {
    restore_calibration();
    print_prompt(0);
  }
}

//! Repeats Linduino loop
void loop()
{
  int16_t user_command;
  static  int16_t selected_dac = 0;     // The selected DAC to be updated (0=A, 1=B ... 8=All).  Initialized to "A".
  // The main control loop
  if (demo_board_connected)             // Do nothing if the demo board is not connected
  {
    if (Serial.available())             // Check for user input
    {
      user_command = read_int();        // Read the user command
      Serial.println(user_command);
      Serial.flush();
      switch (user_command)
      {
        case 1:
          menu_1_select_dac(&selected_dac);
          break;
        case 2:
          menu_2_write_to_input_register(selected_dac);
          break;
        case 3:
          menu_3_write_and_update_dac(selected_dac);
          break;
        case 4:
          menu_4_update_power_up_dac(selected_dac);
          break;
        case 5:
          menu_5_power_down_dac(selected_dac);
          break;
        case 6:
          menu_6_set_reference_mode();
          break;
        case 7:
          menu_7_calibrate_dacs();
          restore_calibration();
          break;
        default:
          Serial.println("Incorrect Option");
          break;
      }
      Serial.println("\n*****************************************************************");
      print_prompt(selected_dac);
    }
  }
}

// Function Definitions

//! Select which DAC to operate on
void menu_1_select_dac(int16_t *selected_dac)
{
  // Select a DAC to operate on
  Serial.print(F("Select DAC to operate on (0=A, 1=B, 2=C, 3=D, 4=E, 5=F, 6=G, 7=H, 8=All): "));
  *selected_dac = read_int();
  if (*selected_dac != num_of_channels)
    Serial.println((char) (*selected_dac + 0x41));
  else
    Serial.println(F("All"));
}

//! Write data to input register, but do not update DAC output
void menu_2_write_to_input_register(int16_t selected_dac)
{
  uint16_t dac_code;

  if (prompt_voltage_or_code() == PROMPT_VOLTAGE)
    dac_code = get_voltage(LTC2636_lsb[selected_dac], LTC2636_offset[selected_dac]);
  else
    dac_code = get_code();
  LTC2636_write(LTC2636_CS, LTC2636_CMD_WRITE, address_map[selected_dac], dac_code << shift_count);
}

//!Write data to DAC register (which updates output immediately)
void menu_3_write_and_update_dac(int16_t selected_dac)
{
  uint16_t dac_code;

  if (prompt_voltage_or_code() == PROMPT_VOLTAGE)
    dac_code = get_voltage(LTC2636_lsb[selected_dac], LTC2636_offset[selected_dac]);
  else
    dac_code = get_code();
  Serial.print("Code: ");
  Serial.println(dac_code, HEX);
  LTC2636_write(LTC2636_CS,LTC2636_CMD_WRITE_UPDATE, address_map[selected_dac], dac_code << shift_count);
}

//! Update DAC with data that is stored in input register, power up if sleeping
void menu_4_update_power_up_dac(int16_t selected_dac)
{
  // Update DAC
  LTC2636_write(LTC2636_CS,LTC2636_CMD_UPDATE, address_map[selected_dac], 0x0000);
  Serial.print("DAC ");
  if (selected_dac != num_of_channels)
    Serial.print((char) (selected_dac + 0x41));
  else
    Serial.print("All");
  Serial.println(" powered up!");
}

//! Power down DAC
void menu_5_power_down_dac(int16_t selected_dac)
{
  // Power down DAC
  LTC2636_write(LTC2636_CS,LTC2636_CMD_POWER_DOWN, address_map[selected_dac], 0x0000);
  Serial.print("DAC ");
  if (selected_dac != num_of_channels)
    Serial.print((char) (selected_dac + 0x41));
  else
    Serial.print("All");
  Serial.println(" powered down!");
}

//! Set reference mode and store to EEPROM
void menu_6_set_reference_mode(void) // int, ext, if ext, prompt for voltage
{
  int16_t user_input;
  Serial.println("Select reference mode - 0 for Internal, 1 for External");
  user_input = read_int();
  if (user_input == 1)
  {
    reference_mode = REF_EXTERNAL;
    Serial.println(F("External reference mode selected"));
  }
  else
  {
    reference_mode = REF_INTERNAL;
    Serial.println(F("Internal reference mode selected"));
  }
  restore_calibration();
}

//! Calibrate all DACs by measuring two known outputs
//! @return 0
int8_t menu_7_calibrate_dacs()
{
  // Calibrate the DACs using a multi-meter
  uint8_t i;
  for (i = 0; i < num_of_channels; i++)
  {
    calibrate_dac(i);   // Run calibration routine
  }
  return (0);
}

//! Read stored calibration parameters from nonvolatile EEPROM on demo board
//! @return void
void restore_calibration()
{
  uint8_t i;
  float dac_count;                                  // The number of codes, 4096 for 12 bits, 65536 for 16 bits

  if (reference_mode == REF_EXTERNAL)
  {
    Serial.println(F("External reference mode set"));
    Serial.print("Enter external reference voltage: ");
    reference_voltage = read_float();
    Serial.print(reference_voltage, 3);
    Serial.println("V");
  }
  else  // EITHER reference is set to internal, OR not programmed in which case default to internal
  {
    reference_mode = REF_INTERNAL; // Redundant if already set
    Serial.println("Internal reference mode set");
  }
  LTC2636_write(LTC2636_CS, reference_mode, LTC2636_DAC_ALL, 0x0000);
  // The following two IF statements are used to allow the program to run with
  // a QuikEval string that does not contain the demo board option.
  // If the demo board option is found then these values are overwritten.
  if (strcmp(demo_board.product_name, "LTC2636-LM") == 0)
  {
    // LTC2636-LM, 12-bits, 2.5V full scale
    shift_count = 4;
    if (reference_mode == REF_INTERNAL)
    {
      reference_voltage = 2.5;
      Serial.println("Internal reference voltage = 2.5 V");
    }
    dac_count = 4096;
  }
  if (strcmp(demo_board.product_name, "LTC2636-HZ") == 0)
  {
    // LTC2636-HZ, 12-bits, 4.096V full scale
    shift_count = 4;
    if (reference_mode == REF_INTERNAL)
    {
      reference_voltage = 4.096;
      Serial.println("Internal reference voltage = 4.096 V");
    }
    dac_count = 4096;
  }
  if (strcmp(demo_board.product_name, "LTC2636-HM") == 0)
  {
    // LTC2636-HM, 12-bits, 4.096V full scale
    shift_count = 4;
    if (reference_mode == REF_INTERNAL)
    {
      reference_voltage = 4.096;
      Serial.println("Internal reference voltage = 4.096 V");
    }
    dac_count = 4096;
  }
  if (strcmp(demo_board.product_name, "LTC2636-LZ") == 0)
  {
    // LTC2636-LZ, 12-bits, 4.096V full scale
    shift_count = 4;
    if (reference_mode == REF_INTERNAL)
    {
      reference_voltage = 4.096;
      Serial.println("Internal reference voltage = 4.096 V");
    }
    dac_count = 4096;
  }

  for (i = 0; i <= num_of_channels; i++)
  {
    LTC2636_offset[i] = 0;
    LTC2636_lsb[i] = reference_voltage / dac_count;
  }
}

//! Prints the title block when program first starts.
void print_title()
{
  Serial.println("");
  Serial.println(F("*****************************************************************"));
  Serial.println(F("* DC1678 Demonstration Program                                  *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* This program demonstrates how to send data to the LTC2636     *"));
  Serial.println(F("* quad 16/12-bit DAC found on the DC1678 demo board.            *"));
  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(int16_t selected_dac)
{
  Serial.println(F("\nCommand Summary:"));
  Serial.println(F("  1-Select DAC"));
  Serial.println(F("  2-Write to input register (no update)"));
  Serial.println(F("  3-Write and update DAC"));
  Serial.println(F("  4-Update / power up DAC"));
  Serial.println(F("  5-Power down DAC"));
  Serial.println(F("  6-Set reference mode"));
  Serial.println(F("  7-Calibrate DAC"));

  Serial.println("\nPresent Values:");
  Serial.print("  Selected DAC: ");
  if (selected_dac != num_of_channels)
    Serial.println((char) (selected_dac + 0x41));
  else
    Serial.println("All");
  Serial.print("  DAC Reference: ");
  if (reference_mode == REF_INTERNAL)
    Serial.println("Internal");
  else
  {
    Serial.print(F("External "));
    Serial.print(reference_voltage, 3);
    Serial.println(F("V reference, please verify"));
  }
  Serial.print(F("Enter a command: "));
  Serial.flush();
}

//! Prompt user to enter a voltage or digital code to send to DAC
//! @returns user input
int16_t prompt_voltage_or_code()
{
  int16_t user_input;
  Serial.print(F("Type 1 to enter voltage, 2 to enter code:"));
  Serial.flush();
  user_input = read_int();
  Serial.println(user_input);

  if (user_input != 2)
    return(PROMPT_VOLTAGE);
  else
    return(PROMPT_CODE);
}

//! Get voltage from user input, calculate DAC code based on lsb, offset
//! @returns the DAC code
uint16_t get_voltage(float LTC2636_lsb, int16_t LTC2636_offset)
{
  float dac_voltage;

  Serial.print(F("Enter Desired DAC output voltage: "));
  dac_voltage = read_float();
  Serial.print(dac_voltage, 3);
  Serial.println(" V");
  Serial.flush();
  return(LTC2636_voltage_to_code(dac_voltage, LTC2636_lsb, LTC2636_offset));
}

//! Get code to send to DAC directly, in decimal, hex, or binary
//! @return code from user
uint16_t get_code()
{
  uint16_t returncode;
  Serial.println("Enter Desired DAC Code");
  Serial.print("(Format 32768, 0x8000, 0100000, or B1000000000000000): ");
  returncode = (uint16_t) read_int();
  Serial.print("0x");
  Serial.println(returncode, HEX);
  Serial.flush();
  return(returncode);
}

//! Calibrate the selected DAC using a voltmeter. The routine
//! does a linear curve fit given two data points.
//! @return ACK bit (0=acknowledge, 1=no acknowledge)
int8_t calibrate_dac(uint8_t index)
{
  int8_t ack=0;
  uint16_t code1 = 0x0200;                            //! Calibration code 1
  uint16_t code2 = 0x0FFF;                            //! Calibration code 2
  float voltage1;                                     //! Calibration voltage 1
  float voltage2;                                     //! Calibration voltage 2
  Serial.println("");
  Serial.print("Calibrating DAC ");
  Serial.println((char) (0x41 + index));
  // Left align 12-bit code1 to 16 bits & write to DAC
  LTC2636_write(LTC2636_CS, LTC2636_CMD_WRITE_UPDATE, index, code1 << shift_count);
  Serial.print("DAC code set to 0x");
  Serial.println(code1, HEX);
  Serial.print("Enter measured DAC voltage:");
  voltage1 = read_float();
  Serial.print(voltage1, 6);
  Serial.println(" V");
  // Left align 12-bit code2 to 16 bits & write to DAC
  LTC2636_write(LTC2636_CS, LTC2636_CMD_WRITE_UPDATE, index, code2 << shift_count);
  Serial.print("DAC code set to 0x");
  Serial.println(code2, HEX);
  Serial.print("Enter measured DAC voltage:");
  voltage2 = read_float();
  Serial.print(voltage2, 6);
  Serial.println(" V");
  LTC2636_calibrate(code1, code2, voltage1, voltage2, &LTC2636_lsb[index], &LTC2636_offset[index]);
  return(ack);
}

/*!
LTC2636: Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.
LTC2634: Quad 12-/10-/8-Bit Rail-to-Rail DACs with 10ppm/°C Reference.

@verbatim

The LTC2636 is a family of quad 16-/12-bit rail-to-rail DACs with integrated
10ppm/C maximum reference. The DACs have built-in high performance, rail-to-
rail, output buffers and are guaranteed monotonic. The LTC2636-L has a full-
scale output of 2.5V with the integrated reference and operates from a single
2.7V to 5.5V supply. The LTC2636-H has a full-scale output of 4.096V with the
integrated reference and operates from a 4.5V to 5.5V supply. Each DAC can also
operate with an external reference, which sets the full-scale output to 2 times
the external reference voltage. These DACs communicate via a SPI/MICROWIRE
compatible 4-wire serial interface which operates at clock rates up to 50MHz.
The LTC2636 incorporates a power-on reset circuit that is controlled by the
PORSEL pin. If PORSEL is tied to GND, the DACs reset to zero-scale. If PORSEL is
tied to VCC, the DACs reset to mid-scale.

SPI DATA FORMAT (MSB First):

24-Bit Load Sequence:

             Byte #1                   Byte #2                         Byte #3
             Command                   MSB                             LSB
LTC2636-12 : C3 C2 C1 C0 A3 A2 A1 A0   D11 D10 D9  D8  D7  D6  D5 D4   D3 D2 D1 D0 X  X  X  X
LTC2636-10 : C3 C2 C1 C0 A3 A2 A1 A0   D9  D8  D7  D6  D5  D4  D3 D2   D1 D0 X  X  X  X  X  X
LTC2636-8  : C3 C2 C1 C0 A3 A2 A1 A0   D7  D6  D5  D4  D3  D2  D1 D0   X  X  X  X  X  X  X  X


32-Bit Load Sequence:

             Byte #1                   Byte #2                   Byte #3                         Byte #4
             Command                   MSB                                                       LSB
LTC2636-12 : X  X  X  X  X  X  X  X    C3 C2 C1 C0 A3 A2 A1 A0   D11 D10 D9  D8  D7  D6  D5 D4   D3 D2 D1 D0 X  X  X  X
LTC2636-10 : X  X  X  X  X  X  X  X    C3 C2 C1 C0 A3 A2 A1 A0   D9  D8  D7  D6  D5  D4  D3 D2   D1 D0 X  X  X  X  X  X
LTC2636-8  : X  X  X  X  X  X  X  X    C3 C2 C1 C0 A3 A2 A1 A0   D7  D6  D5  D4  D3  D2  D1 D0   X  X  X  X  X  X  X  X

Cx   : DAC Command Code
Ax   : DAC Address (0=DACA, 1=DACB, 2=DACC, 3=DACD, 4=DACE, 5=DACF, 6=DACG, 7=DACH, 0xFF=All DACs)
Dx   : DAC Data Bits
X    : Don't care


Example Code:

Set DAC A to 2V for 16-bit DAC.

    shift_count = 0;    // 16-bit DAC does not have to be shifted
    dac_voltage = 2.0;  // Sets dac voltage variable to 2v

    dac_code = LTC2636_voltage_to_code(dac_voltage, LTC2636_lsb, LTC2636_offset);       // Calculate DAC code from voltage, lsb, and offset
    LTC2636_write(LTC2636_CS, LTC2636_CMD_WRITE_UPDATE, LTC2636_DAC_A, dac_code << shift_count);    // Set DAC A with DAC code

@endverbatim

http://www.linear.com/product/LTC2636

http://www.linear.com/product/LTC2634

http://www.linear.com/product/LTC2636#demoboards

http://www.linear.com/product/LTC2634#demoboards

REVISION HISTORY
$Revision: 5080 $
$Date: 2016-05-10 09:31:27 -0700 (Tue, 10 May 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 LTC2636
    Header for LTC2636 Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.
*/

#ifndef LTC2636_H
#define LTC2636_H

#include <SPI.h>

//! Define the SPI CS pin
#ifndef LTC2636_CS
#define LTC2636_CS QUIKEVAL_CS
#endif

//! @name LTC2636 Command Codes
//!@{
//! OR'd together with the DAC address to form the command byte
#define  LTC2636_CMD_WRITE               0x00  //!< Write to input register n
#define  LTC2636_CMD_UPDATE              0x10  //!< Update (power up) DAC register n
#define  LTC2636_CMD_WRITE_UPDATE_ALL    0x20  //!< Write to input register n, update (power up) all
#define  LTC2636_CMD_WRITE_UPDATE        0x30  //!< Write to input register n, update (power up) all
#define  LTC2636_CMD_POWER_DOWN          0x40  //!< Power down n
#define  LTC2636_CMD_POWER_DOWN_ALL      0x50  //!< Power down chip (all DACs and reference)
#define  LTC2636_CMD_INTERNAL_REFERENCE  0x60  //!< Select internal reference (power up reference)
#define  LTC2636_CMD_EXTERNAL_REFERENCE  0x70  //!< Select external reference (power down internal reference)
#define  LTC2636_CMD_NO_OPERATION        0xF0  //!< No operation
//!@}

//! @name LTC2636 DAC addresses
//! @{
//! Which DAC to operate on
#define  LTC2636_DAC_A     0x00
#define  LTC2636_DAC_B     0x01
#define  LTC2636_DAC_C     0x02
#define  LTC2636_DAC_D     0x03
#define  LTC2636_DAC_E     0x04
#define  LTC2636_DAC_F     0x05
#define  LTC2636_DAC_G     0x06
#define  LTC2636_DAC_H     0x07
#define  LTC2636_DAC_ALL   0x0F
//! @}

//! Write the 16-bit dac_code to the LTC2636
//! @return Void
void LTC2636_write(uint8_t cs,                            //!< Chip Select Pin
                   uint8_t dac_command,                   //!< Command Nibble, left-justified, lower nibble set to zero
                   uint8_t dac_address,                   //!< DAC Address Nibble, right justified, upper nibble set to zero
                   uint16_t dac_code                      //!< 16-bit DAC code
                  );

//! Calculate a LTC2636 DAC code given the desired output voltage, offset, and LSB value
//! @return The 16-bit code to send to the DAC
uint16_t LTC2636_voltage_to_code(float dac_voltage,       //!< Voltage to send to DAC
                                 float LTC2636_lsb,       //!< LSB value (volts)
                                 int16_t LTC2636_offset   //!< Offset (volts)
                                );

//! Calculate the LTC2636 DAC output voltage given the DAC code, offset, and LSB value
//! @return Calculated voltage
float LTC2636_code_to_voltage(uint16_t dac_code,          //!< DAC code
                              float LTC2636_lsb,          //!< LSB value (volts)
                              int16_t LTC2636_offset      //!< Offset (volts)
                             );

//! Calculate the LTC2636 offset and LSB voltages given two measured voltages and their corresponding codes
//! @return Void
void LTC2636_calibrate(uint16_t dac_code1,                //!< First DAC code
                       uint16_t dac_code2,                //!< Second DAC code
                       float voltage1,                    //!< First voltage
                       float voltage2,                    //!< Second voltage
                       float *LTC2636_lsb,                //!< Returns resulting LSB (volts)
                       int16_t *LTC2636_offset            //!< Returns resulting Offset (volts)
                      );
#endif  // LTC2636_H

/*!
LTC2636: Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.
LTC2634: Quad 12-/10-/8-Bit Rail-to-Rail DACs with 10ppm/°C Reference.

@verbatim

The LTC2636 is a family of quad 16-/12-bit rail-to-rail DACs with integrated
10ppm/C maximum reference. The DACs have built-in high performance, rail-to-
rail, output buffers and are guaranteed monotonic. The LTC2636-L has a full-
scale output of 2.5V with the integrated reference and operates from a single
2.7V to 5.5V supply. The LTC2636-H has a full-scale output of 4.096V with the
integrated reference and operates from a 4.5V to 5.5V supply. Each DAC can also
operate with an external reference, which sets the full-scale output to 2 times
the external reference voltage. These DACs communicate via a SPI/MICROWIRE
compatible 4-wire serial interface which operates at clock rates up to 50MHz.
The LTC2636 incorporates a power-on reset circuit that is controlled by the
PORSEL pin. If PORSEL is tied to GND, the DACs reset to zero-scale. If PORSEL is
tied to VCC, the DACs reset to mid-scale.

@endverbatim

http://www.linear.com/product/LTC2636

http://www.linear.com/product/LTC2634

http://www.linear.com/product/LTC2636#demoboards

http://www.linear.com/product/LTC2634#demoboards

REVISION HISTORY
$Revision: 5080 $
$Date: 2016-05-10 09:31:27 -0700 (Tue, 10 May 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 LTC2636 LTC2636: Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.

/*! @file
    @ingroup LTC2636
    Library for LTC2636 Octal 12-/10-/8-Bit SPI VOUT DACs with 10ppm/°C Reference.
*/

#include <stdint.h>
#include <math.h>
#include <Arduino.h>
#include "Linduino.h"
#include "LT_SPI.h"
#include "LTC2636.h"
#include <SPI.h>

// Write the 12-bit dac_code to the LTC2636
void LTC2636_write(uint8_t cs, uint8_t dac_command, uint8_t dac_address, uint16_t dac_code)
{
  uint8_t data_array[3], rx_array[3];
  LT_union_int16_2bytes data;

  data.LT_uint16 = dac_code;

  data_array[2] = dac_command | dac_address;
  data_array[1] = data.LT_byte[1];
  data_array[0] = data.LT_byte[0];

  spi_transfer_block(cs, data_array, rx_array, (uint8_t) 3);
}

// Calculate a LTC2636 DAC code given the desired output voltage and DAC address (0-3)
uint16_t LTC2636_voltage_to_code(float dac_voltage, float LTC2636_lsb, int16_t LTC2636_offset)
{
  int32_t dac_code;
  float float_code;
  float_code = dac_voltage / LTC2636_lsb;                                                             //! 1) Calculate the DAC code
  float_code = (float_code > (floor(float_code) + 0.5)) ? ceil(float_code) : floor(float_code);       //! 2) Round
  dac_code = (int32_t)float_code - LTC2636_offset;                                                    //! 3) Subtract offset
  if (dac_code < 0)                                                                                   //! 4) If DAC code < 0, Then DAC code = 0
    dac_code = 0;
  return ((uint16_t)dac_code);                                                                        //! 5) Cast DAC code as uint16_t
}

// Calculate the LTC2636 DAC output voltage given the DAC code and DAC address (0-3)
float LTC2636_code_to_voltage(uint16_t dac_code, float LTC2636_lsb, int16_t LTC2636_offset)
{
  float dac_voltage;
  dac_voltage = ((float)(dac_code + LTC2636_offset)* LTC2636_lsb);                                    //! 1) Calculates the dac_voltage
  return (dac_voltage);
}

// Calculate the LTC2636 offset and LSB voltage given two measured voltages and their corresponding codes
void LTC2636_calibrate(uint16_t dac_code1, uint16_t dac_code2, float voltage1, float voltage2, float *LTC2636_lsb, int16_t *LTC2636_offset)
{
  float temp_offset;
  *LTC2636_lsb = (voltage2 - voltage1) / ((float) (dac_code2 - dac_code1));                           //! 1) Calculate the LSB
  temp_offset = voltage1/(*LTC2636_lsb) - (float)dac_code1;                                           //! 2) Calculate the offset
  temp_offset = (temp_offset > (floor(temp_offset) + 0.5)) ? ceil(temp_offset) : floor(temp_offset);  //! 3) Round offset
  *LTC2636_offset = (int16_t)temp_offset;                                                             //! 4) Cast as int16_t
}