原文：https://blog.csdn.net/propor/article/details/129667596
本文介绍Linux环境下，对I2C设备进行操作。
在对I2C总线进行操作时，可采用i2c-tools对I2C进行查看及操作，待通过工具可对I2C进行操作后，再编写程序进行操作。
1.i2c-tools的使用
1)安装
sudo apt install i2c-tools
2)查询
i2cdetect -l
执行结果如下，可以看到所有的i2c总线。
单独查看第1组I2C总线下挂接的设备，可采用：
i2cdetect -y 1
执行结果如下，可以看到i2c-1总线下的设备，如0x36。
3)写数据
i2ctransfer -f -y 1 w3@0x36 0x01 0x00 0x01
向0x0100写入0x01，这里总计写入了3个字节的数据(w3)。
4)读数据
i2ctransfer -f -y 1 w2@0x36 0x01 0x00 r1
读取0x0100处数据，按I2C协议，先写入寄存器地址(w2)，再进行读取(r1)。
2.用户空间下的读写操作
1)read,write方式
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
int main(int argc, char **argv)
{
unsigned int fd;
unsigned char buf[16];
fd = open("/dev/i2c-1", O_RDWR);
if (!fd) {
printf(“open device failed!\n”);
return -1;
}
ioctl(fd, I2C_SLAVE, 0x36); //slave address
ioctl(fd, I2C_TIMEOUT, 1); //timeout
ioctl(fd, I2C_RETRIES, 1); //try count
//write data to i2c-1
buf[0] = 0x01;
buf[1] = 0x00;
buf[2] = 0x01;
write(fd, &buf[0], 3);
//read data from i2c-1
buf[0] = 0x01;
buf[1] = 0x00;
write(fd, &buf[0], 2); //write register address first
buf[2] = 0x00;
read(fd, &buf[2], 1); //read data
printf("%d\n", buf[2]);
close(fd);
return 0;
}
2)ioctl方式
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <assert.h>
#include <linux/types.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
int main(int argc, char **argv)
{
struct i2c_rdwr_ioctl_data i2c_queue;
unsigned int fd;
unsigned char buf[3];
int ret;
fd = open("/dev/i2c-1", O_RDWR);
if (!fd) {
printf(“open device failed!\n”);
return -1;
}
i2c_queue.nmsgs = 2;
i2c_queue.msgs = (struct i2c_msgs *)malloc(i2c_queue.nmsgs * sizeof(struct i2c_msg));
if (!i2c_queue.msgs) {
printf(“memory alloc error!\n”);
close(fd);
return 1;
}
ioctl(fd, I2C_TIMEOUT, 2); //timeout
ioctl(fd, I2C_RETRIES, 1); //try count
//write data to i2c-1
i2c_queue.nmsgs = 1;
(i2c_queue.msgs[0]).addr = 0x36;
(work_qurue.msgs[0]).len = 3;
(i2c_queue.msgs[1]).flags = 0;
(i2c_queue.msgs[0]).buf = buf; //(unsigned char *)malloc(3)
(i2c_queue.msgs[0]).buf[0] = 0x01;
(i2c_queue.msgs[0]).buf[1] = 0x00;
(i2c_queue.msgs[0]).buf[2] = 0x01;
ret = ioctl(fd, I2C_RDWR, (unsigned long)&i2c_queue);
if (ret < 0)
printf(“i2c write failed!\n”);
//read data from i2c-1
i2c_queue.nmsgs = 2;
(i2c_queue.msgs[0]).addr = 0x36;
(work_qurue.msgs[0]).len = 2;
(i2c_queue.msgs[0]).flags = 0;
(i2c_queue.msgs[0]).buf = buf;
(i2c_queue.msgs[0]).buf[0] = 0x01;
(i2c_queue.msgs[0]).buf[1] = 0x00;
(i2c_queue.msgs[1]).addr = 0x36;
(work_qurue.msgs[1]).len = 1;
(i2c_queue.msgs[1]).flags = I2C_M_RD;
(i2c_queue.msgs[1]).buf = &buf[2]; //(unsigned char *)malloc(1)
(i2c_queue.msgs[1]).buf[0] = 0;
ret = ioctl(fd, I2C_RDWR, (unsigned long)&i2c_queue);
if (ret < 0)
printf(“i2c read failed!\n”);
else
printf(“%02x\n”, buf[2]);
close(fd);
return 0;
}
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原文链接：https://blog.csdn.net/propor/article/details/129667596