#include <SPI.h>

#define CS 10

void setup() {
  // put your setup code here, to run once:
  
  Serial.begin(115200);
  pinMode(CS, OUTPUT);

  uint16_t data;
  SPI.begin();
  data = readADC(0, 1);
  Serial.println("Data read from channel CH0");
  Serial.println(data);

}

void loop() {
  // put your main code here, to run repeatedly:
  uint16_t data;
  data = readADC(0, 1);
  Serial.println("Data read from channel CH0");
  Serial.println(data);
  delay(100);
}

// channel CH0 - 0, CH1 - 1, CH2 - 2, CH3 - 3
// mode differential - 0, single - 1
uint16_t readADC(uint8_t channel, uint8_t mode)
{
  uint16_t output;
  uint8_t channelBits = channel<<6;
  uint8_t modeBit = mode<<1;
  uint8_t startBits;
 
  //Select ADC
  digitalWrite(CS, LOW); //Select the Connected MCP3208 by pulling _CS_PIN_ LOW.
  if(channel>3) {
    startBits = B00000101 | modeBit;
    SPI.transfer(startBits); //Defines Single mode of Operation for the ADC. D2=1 Start Bit. D1=1 Sinfgle Ended Mode D0=0 For Channel 0-3. 1 For Channel 4-7
  }
  else
    startBits = B00000100 | modeBit;
    SPI.transfer(startBits);

  // Note: simulation purpose. With real chip it will convert wrongly
  SPI.transfer(channelBits);

  uint8_t msb = SPI.transfer(channelBits); //Transfers 2nd Byte from MCU to MCP3208 which returns  MSB of the read data. 
  uint8_t lsb = SPI.transfer(0x00);//Transfers 3rd Byte from MCU to MCP3208 which returns  LSB of the read data. 

  digitalWrite(CS,HIGH); //Deselect the Connected MCP3208 by pulling _CS_PIN_ HIGH.
 
  msb = msb & B00001111; // Make all 4 Higher bits of the MSB 0 as 12 Bit Resolution is provided by MCP3208
  
  output = msb<<8 | lsb; //Combine MSB with LSB to form the 12 Bit Analog read  Value.

  return output; //Output Value
}