CPiE3Programs

Page 15 of 21

Chapter 18

#include <bcm2835.h>

#include <stdio.h>

#include <stdlib.h>

int main(int argc, char **argv)

{

if (!bcm2835_init())

{

return 1;

}

if (!bcm2835_spi_begin())

{

return 1;

}

bcm2835_spi_setDataMode(BCM2835_SPI_MODE0);

bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_8192);

bcm2835_spi_chipSelect(BCM2835_SPI_CS0);

bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW);

bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST);

char buf[] = {0x01, 0x80, 0x00};

char readBuf[3];

bcm2835_spi_transfernb(buf, readBuf, 3);

int data = ((int)readBuf[1] & 0x03) << 8 | (int)readBuf[2];

float volts = (float)data * 3.3f / 1023.0f;

printf("%f", volts);

bcm2835_spi_end();

bcm2835_close();

return (EXIT_SUCCESS);

}