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/* ltc2440 <------------------------> Arduino

 * 11: CS to digital pin 10 (SS pin)

 *  7: SDI to digital pin 11 (MOSI pin) 

 * 12: SDO to digital pin 12 (MISO pin) 

 * 13: SCK to digital pin 13 (SCK pin)  

 * 15: BUSY to digital pin 4  

 * 14: f0 - ground  

 * 10: EXT - ground

 *  1: GND - ground 

 *  2: VCC - 5V supply  

 */

int i=0;

int LED;

#include <SPI.h>  // include the SPI library

// set I/O pins used in addition to clock, data in, data out

const byte slaveSelectPin = 10;  // digital pin 10 for /CS

#define DATAREADY 4

void setup() {

  // put your setup code here, to run once:

    pinMode (DATAREADY, INPUT);         // Pin 4

    pinMode (slaveSelectPin, OUTPUT);   // SS Pin 10

    digitalWrite(slaveSelectPin,HIGH);  // chip select is active low

    SPI.begin(); // initialize SPI, covering MOSI,MISO,SCK signals

    SPI.setBitOrder(MSBFIRST);  // data is clocked in MSB first

    SPI.setDataMode(SPI_MODE0);  // SCLK idle low (CPOL=0), MOSI read on rising edge (CPHI=0)

    SPI.setClockDivider(SPI_CLOCK_DIV2);  // system clock = 16 MHz, chip max = 1 MHz

pinMode(5,OUTPUT);    //IR LED

pinMode(7,OUTPUT);    //Red LED

Serial.begin(250000);

}

//====================================

//Main LOOP

//====================================

void loop() {

  // put your main code here, to run repeatedly:

double volts;

unsigned long in;         // incoming serial 32-bit word

unsigned long sum = 0; 

int s=0;

  if (s==0)                                           

    {

    PORTD |= _BV(LED);

    delay(5);

    digitalWrite(slaveSelectPin,LOW);

    digitalWrite(slaveSelectPin,HIGH);

    if(digitalRead(DATAREADY)==LOW)                                           

   {

     in = SpiRead();

        in &= 0B00011111111111111111111111111111;//0x1FFFFFFF; // force high three bits to zero

        in = in>>5;   // move lowest 5 bits LSB

        sum = in;     

        volts = sum *(0.03680586815)

        Serial.println(volts);       

        PORTD &= ~_BV(LED);

    if(i==1){

      i=0;

    } else { 

      i=1;

    }

   }

    s=1;

    }

 if (s==1){          

    if(i==1){

     LED=5;    //ir

     } else {  

    LED=7;   //red

     s=0;

    }

 }

 }

// =================================================================

// SpiRead() -- read out 4 bytes from LTC2440 chip via SPI interface

// =================================================================

unsigned long SpiRead(void) {

 unsigned long result = 0;

 unsigned long b;

  digitalWrite(slaveSelectPin,LOW);   // take the SS pin low to select the chip

  b = SPI.transfer(0x28);   // B3

  result = b<<8;

  b = SPI.transfer(0);   // B2

  result |= b;

  result = result<<8;

  b = SPI.transfer(0);   // B1

  result |= b;

  result = result<<8;

  b = SPI.transfer(0);   // B0

  result |= b;

  // take the SS pin high to de-select the chip:

  digitalWrite(slaveSelectPin,HIGH);

  return(result);//}

}