Linux下iic(i2c)读写AT24C02
linux内核上已有iic的驱动,因此只需要对该iic设备文件进行读写则能够控制外围的iic器件。这里以AT24C02为对象,编写一个简单的读写应用程序。iic设备文件在我的开发板上 /dev/i2c/0 ,打开文件为可读写。AT24C02的器件地址为0x50 ,既是iic总线上从器件的地址,每次只读写一字节数据。
/************************************************************/
//文件名:app_at24c02.c
//功能:测试linux下iic读写at24c02程序
//使用说明: (1)
// (2)
// (3)
// (4)
//作者:jammy-lee
//日期:2010-02-08
/************************************************************/
//包含头文件
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>
#include <errno.h>
//宏定义
#define Address 0x50 //at24c02地址
#define I2C_RETRIES 0x0701
#define I2C_TIMEOUT 0x0702
#define I2C_SLAVE 0x0703 //IIC从器件的地址设置
#define I2C_BUS_MODE 0x0780
typedef unsigned char uint8;
uint8 rbuf[8] = {0x00}; //读出缓存
uint8 wbuf[8] = {0x01,0x05,0x06,0x04,0x01,0x01,0x03,0x0d}; //写入缓存
int fd = -1;
//函数声明
static uint8 AT24C02_Init(void);
static uint8 i2c_write(int fd, uint8 reg, uint8 val);
static uint8 i2c_read(int fd, uint8 reg, uint8 *val);
static uint8 printarray(uint8 Array[], uint8 Num);
//at24c02初始化
static uint8 AT24C02_Init(void)
{
fd = open("/dev/i2c/0", O_RDWR); //允许读写
if(fd < 0)
{
perror("Can't open /dev/nrf24l01 \n"); //打开iic设备文件失败
exit(1);
}
printf("open /dev/i2c/0 success !\n"); //打开iic设备文件成功
if(ioctl(fd, I2C_SLAVE, Address)<0) { //设置iic从器件地址
printf("fail to set i2c device slave address!\n");
close(fd);
return -1;
}
printf("set slave address to 0x%x success!\n", Address);
if(ioctl(fd, I2C_BUS_MODE, 1)<0) //设置iic总线模式
printf("set bus mode fail!\n");
else
printf("set bus mode ok!\n");
return(1);
}
/*
uint8 AT24C02_Write(uint8 *nData, uint8 Reg, uint8 Num)
{
write(fd, &Reg, 1); //
usleep(100); //延时100us
write(fd, nData, Num);
usleep(1000*4); //延时 4ms
return(1);
}
uint8 AT24C02_Read(uint8 nData[], uint8 Reg, uint8 Num)
{
write(fd, &Reg, 1);
usleep(100); //延时100us
read(fd, nData, Num);
usleep(1000*4); //延时 4ms
return(1);
}
*/
//at24c02写入一字节
static uint8 i2c_write(int fd, uint8 reg, uint8 val)
{
int retries;
uint8 data[2];
data[0] = reg;
data[1] = val;
for(retries=5; retries; retries--) {
if(write(fd, data, 2)==2)
return 0;
usleep(1000*10);
}
return -1;
}
//at24c02读取一字节
static uint8 i2c_read(int fd, uint8 reg, uint8 *val)
{
int retries;
for(retries=5; retries; retries--)
if(write(fd, ®, 1)==1)
if(read(fd, val, 1)==1)
return 0;
return -1;
}
//输出数组
static uint8 printarray(uint8 Array[], uint8 Num)
{
uint8 i;
for(i=0;i<Num;i++)
{
printf("Data [%d] is %d \n", i ,Array[i]);
}
return(1);
}
//主函数
int main(int argc, char *argv[])
{
int i;
AT24C02_Init();
usleep(1000*100);
for(i=0; i<sizeof(rbuf); i++)
if(i2c_read(fd, i, &rbuf[i]))
break;
printarray(rbuf ,8);
printf("Before Write Data \n");
sleep(1);
for(i=0; i<sizeof(rbuf); i++)
if(i2c_write(fd, i, wbuf[i]))
break;
printarray(wbuf ,8);
printf("Writing Data \n");
sleep(1);
for(i=0; i<sizeof(rbuf); i++)
if(i2c_read(fd, i, &rbuf[i]))
break;
printarray(rbuf ,8);
printf("After Write Data \n");
close(fd);
}