linux系统之字符设备驱动——IIC驱动mma8451q

linux系统之字符设备驱动——IIC子系统驱动mma8451q

1. 原理图

2. 驱动程序

mma8451q.c

/*
 * @Author: your name
 * @Date: 2021-02-23 22:16:37
 * @LastEditTime: 2021-02-24 13:57:31
 * @LastEditors: Please set LastEditors
 * @Description: In User Settings Edit
 * @FilePath: \6_I2Cmma8451q\mma8451q.c
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/cdev.h>
#include <linux/slab.h>

#include "mma8451q.h"
#define WHO_AM_I 	0x0d
#define NAME 		"mma8451q"	// 设备节点名字

struct mma8451q_dev{
	unsigned int major;
    struct class *class;	// 设备节点目录
    struct device *dev; 	// 设备
	struct i2c_client *client;		// i2c子系统
}mma8451qDevice;

/**
 * 使用i2c子系统读写寄存器
*/
int i2c_write_reg(unsigned char regaddr, char value)
{
	int ret = 0;
	char w_buf[] = {regaddr, value};	// 关键就在这

	struct i2c_msg w_msg = {
		.addr = mma8451qDevice.client->addr,	// 从机设备地址
		.flags = 0,			// 0:写，1:I2C_M_RD读，I2C_M_TEN：10位从机地址
		.len = 2,			// 消息的长度
		.buf = w_buf,		// 消息的首地址
	};

	ret = i2c_transfer(mma8451qDevice.client->adapter, &w_msg, 1);		// 有几个起始位，就有几个消息
	if(ret != 1)
	{
		printk("sned i2c msg error!\n");
		return -EAGAIN;
	}
	return 0;
}
int i2c_read_reg(unsigned char regaddr)
{
	int ret = 0;
	char value;
	char r_buf[] = {regaddr};
	struct i2c_msg r_msg[] = {
		[0] = {
			.addr = mma8451qDevice.client->addr,
			.flags = 0,
			.len = 1,
			.buf = r_buf,
		},
		[1] = {
			.addr = mma8451qDevice.client->addr,
			.flags = I2C_M_RD,
			.len = 1,
			.buf = &value,
		},
	};

	ret = i2c_transfer(mma8451qDevice.client->adapter, r_msg, 2);
	if(ret != 2)
	{
		printk("recvive i2c msg error!\n");
		return -EAGAIN;
	}
	return value;
}
int mma8451q_open (struct inode *inode, struct file *file)
{
	printk("mma8451q_open OK!\n");
	return 0;
}
int mma8451q_close (struct inode *inode, struct file *file)
{
	printk("mma8451q_close OK!\n");
	return 0;
}
ssize_t mma8451q_read (struct file *file, char __user *ubuf, size_t size, loff_t *loff)
{
	int ret = 0;
	char x_H, x_L, y_H, y_L, z_H, z_L;
	short x, y, z;
	struct mma8451q_accData{
		short x_acc;
		short y_acc;
		short z_acc;
	}acc_data;
	if(size > sizeof(struct mma8451q_accData))
		size = sizeof(struct mma8451q_accData);

	x_H = i2c_read_reg(0x01);
	x_L = i2c_read_reg(0x02);
	x = x_H;
	x = x << 8 | x_L;
	acc_data.x_acc = x >> 2;

	y_H = i2c_read_reg(0x01);
	y_L = i2c_read_reg(0x02);
	y = y_H;
	y = y << 8 | y_L;
	acc_data.y_acc = y >> 2;

	z_H = i2c_read_reg(0x01);
	z_L = i2c_read_reg(0x02);
	z = z_H;
	z = z << 8 | z_L;
	acc_data.z_acc = z >> 2;
	
	ret = copy_to_user(ubuf, &acc_data, size);
	if(ret)
	{
		printk("copy data to user error\n");
		return -EINVAL;
	}
	return size;
}
const struct file_operations fops = 
{
	.open = mma8451q_open,
    .release = mma8451q_close,
	.read = mma8451q_read,
};
int mma8451q_probe(struct i2c_client *cli, const struct i2c_device_id *id)
{
	int ret = -1;
	mma8451qDevice.client = cli;

	printk("mma8451q_probe started\n");

	// 1. 注册字符设备驱动
	mma8451qDevice.major = register_chrdev(mma8451qDevice.major, NAME, &fops);
	if(mma8451qDevice.major < 0)
	{
		printk("register_chrdev Error!\n");
		goto ERR1;
	}
	// 2. 创建设备驱动目录
    mma8451qDevice.class = class_create(THIS_MODULE, "cmma8451qdev");
	if(IS_ERR(mma8451qDevice.class)){
		printk("class_create Error!\n");
		goto ERR2;
	}
    // 3. 创建设备驱动节点
    mma8451qDevice.dev = device_create(mma8451qDevice.class, NULL, MKDEV(mma8451qDevice.major, 0), NULL, NAME);
	if(IS_ERR(mma8451qDevice.dev)){
		printk("device_create Error!\n");
		ret = PTR_ERR(mma8451qDevice.dev);
		goto ERR3;
	}

	// mmq8451q设备的初始化
	ret = i2c_read_reg(WHO_AM_I);
	printk("WHO_AM_I(0x1a) = %#x\n", ret);
	printk("mma8451q_probe OK!\n");

	i2c_write_reg(0x2A, 0X01);		// 激活设备
	i2c_write_reg(0x2B, 0X02);		// 高精度模式
	return 0;

ERR3:
	class_destroy(mma8451qDevice.class);
ERR2:
	unregister_chrdev(mma8451qDevice.major, NAME);
ERR1:
	return ret;
}
int mma8451q_remove(struct i2c_client *cli)
{
	device_destroy(mma8451qDevice.class, MKDEV(mma8451qDevice.major, 0));
    // 3. 销毁设备驱动目录
	class_destroy(mma8451qDevice.class);
    // 4. 注销字符设备驱动
    unregister_chrdev(mma8451qDevice.major, NAME);

	printk("mma8451q_remove OK!\n");
	return 0;
}

struct i2c_device_id mma8451q_id_table[] = {
	{"mma8451q", 0},
	{},
};
struct i2c_driver mma8451q_driver = {
	.probe = mma8451q_probe,
	.remove = mma8451q_remove,
	.driver = {
		.name = "mma8451q",
	},
	.id_table = mma8451q_id_table,
};

static int __init mma8451q_Init(void)
{
	return i2c_add_driver(&mma8451q_driver);
}
static void __exit mma8451q_Exit(void)
{
	i2c_del_driver(&mma8451q_driver);
}

module_init(mma8451q_Init);
module_exit(mma8451q_Exit);
MODULE_LICENSE("GPL");

1. 应用程序 main.c

/*
 * @Author: your name
 * @Date: 2021-02-23 20:09:13
 * @LastEditTime: 2021-02-24 14:55:45
 * @LastEditors: Please set LastEditors
 * @Description: In User Settings Edit
 * @FilePath: \2-led\main.c
 */


#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

struct mma8451qData
{
    short acc_x;
    short acc_y;
    short acc_z;
}acc_data;
#define g 9.8
float GetAccelerated(short acc)  
{
    return 4*g*acc/32768;
}
int main(int argc, char const *argv[])
{
    int fd = open("/dev/mma8451q", O_RDWR);
    if(fd < 0)
    {
         perror("open");
         return -1;  
    }

    while(1)
    {
        read(fd, &acc_data, sizeof(struct mma8451qData));
        printf("%.4f\t%.4f,\t%.4f\r\n", GetAccelerated(acc_data.acc_x), GetAccelerated(acc_data.acc_y), GetAccelerated(acc_data.acc_z));
        usleep(100000);
    }
    close(fd);

    return 0;
}

3. 下载调试

这两个地方需要添加，才可以正常运行。