#include <SPI.h>
#define CHIP_SEL_DAC 31

uint32_t sample_data = 0b00000000000000000000000000000000;
                                                                          // { PRFX , CTRL , ADDR , DDDDAAAATTTTAAAA , FTUR }
uint32_t set_a_to_2_5   = 0b00000010000001111111111111110000;             // { 0000 , 0010 , 0000 , 0111111111111111 , 0000 }
uint32_t set_a_to_1_25  = 0b00000010000000111111111111110000;             // { 0000 , 0010 , 0000 , 0011111111111111 , 0000 }
uint32_t set_b_to_1_25  = 0b00000010000100111111111111110000;             // { 0000 , 0010 , 0001 , 0011111111111111 , 0000 }
uint32_t set_c_to_0_625  = 0b00000010001000011111111111110000;            // { 0000 , 0010 , 0010 , 0001111111111111 , 0000 }
uint32_t set_d_to_0_3125 = 0b00000010001100001111111111110000;            // { 0000 , 0010 , 0011 , 0000111111111111 , 0000 }
uint32_t set_g_to_2_5   = 0b00000010010101111111111111110000;             // { 0000 , 0010 , 0101 , 0111111111111111 , 0000 }
uint32_t int_ref_on_flexible_mode = 0b00001001000010100000000000000000;   // { 0000 , 1001 , 0000 , 1010000000000000 , 0000 }

void setup() {
  delay(1000);
  // Turn off LED's
  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT);
  pinMode(18, OUTPUT);
  pinMode(19, OUTPUT);
  digitalWrite(16, LOW);
  digitalWrite(17, LOW);
  digitalWrite(18, LOW);
  digitalWrite(19, LOW);
  // set the chip select pin as an output:
  pinMode (CHIP_SEL_DAC, OUTPUT);
  // initialize SPI1:
  SPI1.setDataMode(SPI_MODE1);
  SPI1.begin();
  delay(20);


  SPI1.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1));
  digitalWrite(CHIP_SEL_DAC,LOW);
  delayMicroseconds(1);
  SPI1.transfer(int_ref_on_flexible_mode >> 24);
  SPI1.transfer(int_ref_on_flexible_mode >> 16);
  SPI1.transfer(int_ref_on_flexible_mode >> 8);
  SPI1.transfer(int_ref_on_flexible_mode);
  digitalWrite(CHIP_SEL_DAC,HIGH);
  SPI1.endTransaction();
  delay(1000);

}

void loop() {
  SPI1.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1));
  digitalWrite(CHIP_SEL_DAC, LOW);
  SPI1.transfer(set_a_to_2_5 >> 24);
  SPI1.transfer(set_a_to_2_5 >> 16);
  SPI1.transfer(set_a_to_2_5 >> 8);
  SPI1.transfer(set_a_to_2_5);
  digitalWrite(CHIP_SEL_DAC, HIGH);
  SPI1.endTransaction();
  delay(1000);
  SPI1.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1));
  digitalWrite(CHIP_SEL_DAC, LOW);
  SPI1.transfer(set_a_to_1_25 >> 24);
  SPI1.transfer(set_a_to_1_25 >> 16);
  SPI1.transfer(set_a_to_1_25 >> 8);
  SPI1.transfer(set_a_to_1_25);
  digitalWrite(CHIP_SEL_DAC, HIGH);
  SPI1.endTransaction();
  delay(1000);
}