通过ioctl I2C_RDWR 实现I2C 用户态测试程序

本测试程序通过 ioctl(fd, I2C_RDWR, &ioctl_data)访问I2C


#include
#include
#include
#include
#include
#include
#include

#define I2C_DEV    "/dev/i2c-0"
#define I2C_PCA9554_ADDR 0x54
#define WRITE_VALUE         0x49

int
main()
{
#if 1
 struct i2c_rdwr_ioctl_data ioctl_data = {0};
 struct i2c_msg msg[4] = {{0}};
 unsigned char data[4] = {0};
 unsigned char out[2] = {0};
 int fd;
 int rc;

 fd = open(I2C_DEV, O_RDWR);
 if (fd < 0) {
  printf("failed to open %s\n", I2C_DEV);
  return (-1);
 }

 /* test reading and writing registers in PCA9554 */

 /* read from Configuration Register (0x03) */
 data[0] = 0x03;
 msg[0].addr = I2C_PCA9554_ADDR;
 msg[0].flags = 0; /* write */
 msg[0].len = 1;
 msg[0].buf = &data[0];
 msg[1].addr = I2C_PCA9554_ADDR;
 msg[1].flags = I2C_M_RD;
 msg[1].len = 1;
 msg[1].buf = &out[0];

 ioctl_data.nmsgs = 2;
 ioctl_data.msgs = &msg[0];
 rc = ioctl(fd, I2C_RDWR, &ioctl_data);
 if (rc < 0) {
  printf("read, I2C_RDWR failed: %d.\n", errno);
  close(fd);
  return (-1);
 }

 printf("Config reg: 0x%02x\n", out[0] );

 /* write 0x5a into Configuration Register (0x03) */
 printf("write 0x%02x at 0x03\n", WRITE_VALUE);
 data[0] = 0x03; /* address */
 data[1] = WRITE_VALUE; /* data */
 msg[0].addr = I2C_PCA9554_ADDR;
 msg[0].flags = 0; /* write */
 msg[0].len = 2;
 msg[0].buf = &data[0];

 ioctl_data.nmsgs = 1;
 ioctl_data.msgs = &msg[0];
 rc = ioctl(fd, I2C_RDWR, &ioctl_data);
 if (rc < 0) {
  printf("write, I2C_RDWR failed: %d.\n", errno);
  close(fd);
  return (-1);
 }

 

 sleep(1);
 /* read out again to check */
 printf("read out at 0x03\n");
 data[0] = 0x03;
 msg[0].addr = I2C_PCA9554_ADDR;
 msg[0].flags = 0; /* write */
 msg[0].len = 1;
 msg[0].buf = &data[0];
 msg[1].addr = I2C_PCA9554_ADDR;
 msg[1].flags = I2C_M_RD;
 msg[1].len = 1;
 msg[1].buf = &out[0];

 ioctl_data.nmsgs = 2;
 ioctl_data.msgs = &msg[0];
 rc = ioctl(fd, I2C_RDWR, &ioctl_data);
 if (rc < 0) {
  printf("read, I2C_RDWR failed: %d.\n", errno);
  close(fd);
  return (-1);
 }

 if (out[0] != WRITE_VALUE)
  printf("write failed. ");
 else
  printf("write success. ");

 printf("Config_reg: 0x%02x\n", out[0] );

 sleep(1);

 close(fd);
#endif

 return (0);
}