嵌入式linux应用读写i2c示例

这里分享一个嵌入式linux读写24c02的i2c程序
ioctl函数的使用:
原型：struct ioctl(struct file *file,unsigned int cmd,unsigned long arg);
cmd有I2C_SLAVE,I2C_SLAVE_FORCE,I2C_TENBIT,I2C_SET_SPEED几个选项；
I2C_SLAVE：对应的arg取值为I2C从机地址，用来设定I2C从机地址；
I2C_SLAVE_FORCE：对应的arg取值为I2C从机地址，用来修改I2C从机地址；
I2C_TENBIT：对应的arg取值为0：从机地址为7 bit；对应的arg取值为1：从机地址为10bit。用来指定I2C从机地址的位数；
I2C_SET_SPEED：对应的arg取值为I2C总线控制器分频值。用来设置I2C总线控制器时钟频率；

常用设置设置I2c从机地址为0xA0，如果选用at24c08设备，那么从机是7 bit地址，所以要右移1位，指定从机地址为7 bit，

i2c.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>

int i2c_init(char *i2c_dev, unsigned char i2c_addr)
{
    
    
	int res = 0;
	
	fd = open(i2c_dev, O_RDWR);
	if(fd < 0)
	{
    
    
		printf("[%s]:[%d] open i2c file error\r\n", __FUNCTION__, __LINE__);
		return -1;
	}
	res = ioctl(fd,I2C_TENBIT,0);
	res = ioctl(fd,I2C_SLAVE, (i2c_addr >> 1));    //设置I2C从设备地址
	
	return res;
}


int i2c_readNbyte(unsigned char *buf, int len)
{
    
    
	int res = 0;
	
	res = read(fd, buf,len);
	return res;
}

int i2c_writeNbyte(unsigned char *buf, int len)
{
    
    
	int res = 0;
	
	res = write(fd, buf,len);
	return res;
}

int i2c_readReg(unsigned int reg_addr, unsigned char *buf, int len)
{
    
    
	int res = 0;
	unsigned char buff[2];
	
	buff[0] = reg_addr >> 8;
	buff[1] = reg_addr & 0xff;
	write(fd, buff, 2);
	res = read(fd, buf,len);
	
	return res;
}

int i2c_writeReg(unsigned int reg_addr, unsigned char *buf, int len)
{
    
    
	int res = 0,i;
	unsigned char *buff = 0;
	
	buff = (unsigned char *)malloc((len+2));
	buff[0] = reg_addr >> 8;
	buff[1] = reg_addr & 0xff;
	for(i = 0; i < len; i++)
		buff[(i+2)] = buf[i];
	res = write(fd, buff, (len+2));
	free(buff);
	
	return res;
}

int i2c_close()
{
    
    
	close(fd);
	return 0;
}

main.c

#include <stdio.h>
#include "i2c.h"

int main()
{
    
    
	unsigned char buff[2] = {
    
    0x12,0x34};
	
	i2c_init("/dev/i2c-1",  0xa0);
	i2c_writeNbyte(buff, 2);
	i2c_readNbyte(buff, 2);
	printf("%x\n",buff[1]);
	i2c_close();
	
	return 0;
}