Linux I2C应用程序

#include <stdio.h>
#include <linux/types.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <assert.h>
#include <string.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>

int main(int argc, char **argv)
{
	struct i2c_rdwr_ioctl_data e2prom_data;
	unsigned int fd;
	unsigned int slave_address, reg_address,value; 
	//slave_address为eeprom的地址，reg_address为eeprom中存储单元的地址，范围0x0--0xFFFFFFFF,value为你要写进eeprom的值
	int ret;
	
	if (argc < 5){
		printf("Usage:\n%s /dev/i2c/x start_addr reg_addr value\n",argv[0]);
		return 0;
	}
	
	fd = open(argv[1], O_RDWR);
	
	if (!fd){
		printf("Error on opening the device file\n");
		return 0;
	}

	sscanf(argv[2], "%x", &slave_address);
	sscanf(argv[3], "%x", &reg_address);
	sscanf(argv[4], "%x", &value);
	
	e2prom_data.nmsgs = 2;//因为都时序要两次，所以设为2
	e2prom_data.msgs = (struct i2c_msg *)malloc(e2prom_data.nmsgs * sizeof(struct i2c_msg));
	if (!e2prom_data.msgs){
		printf("Memory alloc error\n");
		close(fd);
		return 0;
	}
	
	ioctl(fd, I2C_TIMEOUT, 2);//设置超时时间
	ioctl(fd, I2C_RETRIES, 1);//设置重发次数

	/* write data to e2prom*/
	e2prom_data.nmsgs = 1;
	e2prom_data.msgs[0].len = 2;//信息长度为2，看写时序，eeprom的地址不算的，因为付给了addr，而len是指buf中的值的个数
	e2prom_data.msgs[0].addr = slave_address;
	e2prom_data.msgs[0].flags = 0;//写命令
	e2prom_data.msgs[0].buf = (unsigned char*)malloc(2);
	e2prom_data.msgs[0].buf[0] = reg_address;//信息值1 eeprom中存储单元的地址，即你要往哪写
	e2prom_data.msgs[0].buf[1] = value;//信息值2,即你要写什么
	
	ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了 ，写进去吧
	if (ret < 0){
		printf ("ioctl write error\n");
	}

	printf("you have write %02x into e2prom at %02x address\n",value,reg_address);
	
	sleep(1);
	/*read data from e2prom*/
	e2prom_data.nmsgs = 2;//读时序要两次过程，要发两次I2C消息
	e2prom_data.msgs[0].len = 1;//信息长度为1，第一次只写要读的eeprom中存储单元的地址
	e2prom_data.msgs[0].addr = slave_address;
	e2prom_data.msgs[0].flags = 0;//写命令，看读时序理解
	e2prom_data.msgs[0].buf[0] = reg_address;//信息值
		
	e2prom_data.msgs[1].len = 1;
	e2prom_data.msgs[1].addr = slave_address;
	e2prom_data.msgs[1].flags = I2C_M_RD;//读命令
	e2prom_data.msgs[1].buf = (unsigned char*)malloc(1);
	e2prom_data.msgs[1].buf[0] = 0;//先清空要读的缓冲区
	ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了，读吧
	if (ret < 0){
		printf ("ioctl read error\n");
	}
	
	printf("read %02x from e2prom address %02x\n",e2prom_data.msgs[1].buf[0], reg_address);
	
	close(fd);
	return 0;	
}