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dev-interface
- read write
/*************************************************************************
> File Name: i2c-user.c
> Author: Sues
> Mail: [email protected]
> Created Time: Tue 30 Apr 2019 02:15:25 PM CST
************************************************************************/
//Documentation/i2c/dev-interface
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "linux/i2c-dev.h"
/**
* def_config 中的 CONFIG_I2C_CHARDEV 要定义
* 定义之后会出现 /dev/i2c-0 /dev/i2c-1 表示i2c控制器0 1
*/
/*
* /dev/i2c-0是在注册i2c-dev.c后产生的，代表一个可操作的适配器。如果不使用i2c-dev.c
* 的方式，就没有，也不需要这个节点。
* i2c-%d adap->nr ,i2c adpter 的编号 ,不用probe
*/
int main(int argc, char *argv[]){
int file;
int adapter_nr = 2; /* probably dynamically determined */
char filename[20];
int addr = 0x40; /* The I2C address */
__u8 reg = 0x10; /* Device register to access */
__s32 res;
char buf[10];
// 1. open file
snprintf(filename, 19, "/dev/i2c-%d", adapter_nr);
file = open(filename, O_RDWR);
if (file < 0) {
/* ERROR HANDLING; you can check errno to see what went wrong */
exit(1);
}
// 2. do ioctl
if (ioctl(file, I2C_SLAVE, addr) < 0) {
/* ERROR HANDLING; you can check errno to see what went wrong */
exit(1);
}
// 3. write
/* Using I2C Write, equivalent of
i2c_smbus_write_word_data(file, reg, 0x6543) */
buf[0] = reg;
buf[1] = 0x43;
buf[2] = 0x65;
if (write(file, buf, 3) != 3) {
/* ERROR HANDLING: i2c transaction failed */
}
// 4. read
/* Using I2C Read, equivalent of i2c_smbus_read_byte(file) */
if (read(file, buf, 1) != 1) {
/* ERROR HANDLING: i2c transaction failed */
} else {
printf("recv data:%d\n",buf[0]);
/* buf[0] contains the read byte */
}
#if 0
/* Using SMBus commands */
res = i2c_smbus_read_word_data(file, reg);
if (res < 0) {
/* ERROR HANDLING: i2c transaction failed */
} else {
/* res contains the read word */
}
#endif
return 0;
}
- so-called combined transactions
#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 <string.h>
/**
* def_config 中的 CONFIG_I2C_CHARDEV 要定义
* 定义之后会出现 /dev/i2c-0 /dev/i2c-1 表示i2c控制器0 1
*/
/*
* /dev/i2c-0是在注册i2c-dev.c后产生的，代表一个可操作的适配器。如果不使用i2c-dev.c
* 的方式，就没有，也不需要这个节点。
*/
#define I2C_RETRIES 0x0701
#define I2C_TIMEOUT 0x0702
#define I2C_RDWR 0x0707
/*********参数定义与内核一致，路径include/linux/i2c-dev.h*******/
struct i2c_msg
{
unsigned short addr;
unsigned short flags;
#define I2C_M_TEN 0x0010
#define I2C_M_RD 0x0001
unsigned short len;
unsigned char *buf;
};
struct i2c_rdwr_ioctl_data
{
struct i2c_msg *msgs;
int nmsgs;
/* nmsgs这个数量决定了有多少开始信号，对于“单开始时序”，取1*/
};
#define SLAVE_ADDRESS 0x50
#define ADAPTER_NR 1
int main(int argc, char *argv[])
{
struct i2c_rdwr_ioctl_data e2prom_data;
int fd,ret = 0;
char filename[16] = {0};
//1. 打开设备
snprintf(filename, 15, "/dev/i2c-%d", ADAPTER_NR);
fd=open(filename,O_RDWR);
if(fd < 0)
{
perror("open error");
}
//2. 设置
ioctl(fd,I2C_TIMEOUT,1);/*超时时间*/
ioctl(fd,I2C_RETRIES,2);/*重复次数*/
//3. 写
/***write data to e2prom**/
e2prom_data.nmsgs=1;
e2prom_data.msgs=(struct i2c_msg*)malloc(e2prom_data.nmsgs*sizeof(struct i2c_msg));
if(!e2prom_data.msgs)
{
perror("malloc error");
exit(1);
}
(e2prom_data.msgs[0]).len=2; //1个 e2prom 写入目标的地址和1个数据
(e2prom_data.msgs[0]).addr=SLAVE_ADDRESS;//e2prom 设备地址
(e2prom_data.msgs[0]).flags=0; //write
(e2prom_data.msgs[0]).buf=(unsigned char*)malloc(2);
(e2prom_data.msgs[0]).buf[0]=0x10;// e2prom 写入目标的地址
(e2prom_data.msgs[0]).buf[1]=0x58;//the data to write
ret=ioctl(fd,I2C_RDWR,(unsigned long)&e2prom_data);
if(ret<0)
{
perror("ioctl error1");
}
free((e2prom_data.msgs[0]).buf);
(e2prom_data.msgs[0]).buf = NULL;
free(e2prom_data.msgs);
e2prom_data.msgs = NULL;
sleep(1);
// 4. 读
/******read data from e2prom*******/
e2prom_data.nmsgs=2;
e2prom_data.msgs=(struct i2c_msg*)malloc(e2prom_data.nmsgs*sizeof(struct i2c_msg));
if(!e2prom_data.msgs)
{
perror("malloc error");
exit(1);
}
(e2prom_data.msgs[0]).len=1; //e2prom 目标数据的地址
(e2prom_data.msgs[0]).addr=SLAVE_ADDRESS; // e2prom 设备地址
(e2prom_data.msgs[0]).flags=0;//write
(e2prom_data.msgs[0]).buf[0]=0x10;//e2prom数据地址
(e2prom_data.msgs[1]).len=1;//读出的数据
(e2prom_data.msgs[1]).addr=0x50;// e2prom 设备地址
(e2prom_data.msgs[1]).flags=I2C_M_RD;//read
(e2prom_data.msgs[1]).buf=(unsigned char*)malloc(32);//存放返回值的地址。
memset((e2prom_data.msgs[1]).buf,0,32);
ret=ioctl(fd,I2C_RDWR,(unsigned long)&e2prom_data);
if(ret<0)
{
perror("ioctl error2");
}
printf("buff[0]=%x/n",(e2prom_data.msgs[1]).buf[0]);
/***打印读出的值，没错的话，就应该是前面写的0x58了***/
free((e2prom_data.msgs[1]).buf);
free(e2prom_data.msgs);
e2prom_data.msgs = NULL;
// 5. 关闭文件
close(fd);
return 0;
}