Page 9 of 14
Page 167
#define _DEFAULT_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <stdint.h>
FILE *doCommand(char *cmd)
{
FILE *fp = popen(cmd, "r");
if (fp == NULL)
{
printf("Failed to run command %s \n\r", cmd);
exit(1);
}
return fp;
}
void checkSPI0()
{
FILE *fd = doCommand("sudo dtparam -l");
char output[1024];
int txfound = 0;
char indicator[] = "spi=on";
char command[] = "sudo dtparam spi=on";
while (fgets(output, sizeof(output), fd) != NULL)
{
printf("%s\n\r", output);
fflush(stdout);
if (strstr(output, indicator) != NULL)
{
txfound = 1;
}
}
if (txfound == 0)
{
fd = doCommand(command);
sleep(2);
}
pclose(fd);
}
int main(int argc, char **argv)
{
checkSPI0();
uint8_t tx[] = {0xAA};
uint8_t rx[] = {0};
struct spi_ioc_transfer tr =
{
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = 1,
.delay_usecs = 0,
.speed_hz = 500000,
.bits_per_word = 8,
};
int fd = open("/dev/spidev0.0", O_RDWR);
int status = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
if (status < 0)
printf("can't send data");
printf("%X,%X\n", tx[0],rx[0]);
close(fd);
}
Page 177
#define _DEFAULT_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <stdint.h>
FILE *doCommand(char *cmd)
{
FILE *fp = popen(cmd, "r");
if (fp == NULL)
{
printf("Failed to run command %s \n\r", cmd);
exit(1);
}
return fp;
}
void checkSPI0()
{
FILE *fd = doCommand("sudo dtparam -l");
char output[1024];
int txfound = 0;
char indicator[] = "spi=on";
char command[] = "sudo dtparam spi=on";
while (fgets(output, sizeof(output), fd) != NULL)
{
printf("%s\n\r", output);
fflush(stdout);
if (strstr(output, indicator) != NULL)
{
txfound = 1;
}
}
if (txfound == 0)
{
fd = doCommand(command);
sleep(2);
}
pclose(fd);
}
int main(int argc, char **argv)
{
checkSPI0();
uint8_t tx[] = {0x01, 0x80, 0x00};
uint8_t rx[3];
struct spi_ioc_transfer tr =
{
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = 3,
.delay_usecs = 0,
.speed_hz = 0,
.bits_per_word = 0,
};
int fd = open("/dev/spidev0.0", O_RDWR);
static uint8_t mode = 0;
int status = ioctl(fd, SPI_IOC_WR_MODE, &mode);
if (status == -1)
printf("can't set spi mode");
static uint8_t bits = 8;
status = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
if (status == -1)
printf("can't set bits per word");
static uint32_t speed = 100000;
status = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
if (status == -1)
printf("can't set max speed hz");
status = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
if (status < 0)
printf("can't send data");
int data = ((int)rx[1] & 0x03) << 8 | (int)rx[2];
float volts = (((float)data) * 3.3f) / 1023.0f;
printf("%f V\n\r", volts);
close(fd);
}
