AD conversion using MCP3208 on Raspberry Pi convers

read_mcp3208.c

/*
* Before running this program, execute the following initialization command:
* > gpio load spi
*
* Expected result:
* > pi@raspberrypi:~$ ./read_mcp3208
* 
* wiringPiSPISetup status = 3
* wiringPiSPIDataRW status = 3
* data[0]=00
* data[1]=03
* data[2]=f8
* Voltage = 0.620V
* Temperature = 31.38degC
* 
*/

#include <wiringPiSPI.h>
#include <stdio.h>

int main(int argc, char* argv[]){
	//initialize SPI
	int status; status=wiringPiSPISetup(0, 500000);
	printf("wiringPiSPISetup status = %d\n",status);

	//send AD conversion command to MCP3208
	unsigned char data[3]={0x06,0x00,0x00};
	status=wiringPiSPIDataRW(0,data,3);
	printf("wiringPiSPIDataRW status = %d\n",status);
	for(size_t i=0;i<3;i++){
		printf("data[%d]=%02x\n",i,data[i]);
	}

	//convert obtained ADC value to voltage
	short adcValue=(data[1]&0x07)*0x100+data[2];
	const double ADCMax=4096.0;
	const double Vref=2.5;//V
	double voltage=adcValue/ADCMax*Vref;
	printf("Voltage = %.3fV\n",voltage);
		
	//then to temperature
	const double lm60Coefficient=0.00625; //V/deg
	const double lm60Offset=0.424; //V
	double temp=(voltage-lm60Offset)/lm60Coefficient;
	printf("Temperature = %.2fdegC\n",temp);
}