14.Linux I2C驱动
I2C 总线驱动，或者说 I2C 适配器驱动的主要工作就是初始化 i2c_adapter 结构体变量，然后设置 i2c_algorithm 中的 master_xfer 函数。完成以后通过i2c_add_numbered_adapter或 i2c_add_adapter 这两个函数向系统注册设置好的 i2c_adapter
i2c是有自己的总线驱动的，不需要像platform一样添加总线
我是使用的正点原子mini开发板，上面没有i2c连接的设备，我连接一个mpu6050来做测试。
驱动程序¶
修改设备树，在i2c设备中，添加mpu6050节点。
&i2c1 {
clock-frequency = <100000>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_i2c1>;
status = "okay";
mpu6050@68 {
compatible = "alientek,mpu6050";
reg = <0x68>;
};
};
包含所需头文件
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/semaphore.h>
#include <linux/timer.h>
#include <linux/i2c.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>
然后写驱动出入口相关函数，这里知道i2c_add_driver是添加一个iic设备，i2c_del_driver是卸载。这里i2c驱动结构体结构体还未定义。
static int __init mpu6050_init(void)
{
int ret = 0;
ret = i2c_add_driver(&mpu6050_driver);
return ret;
}
static void __exit mpu6050_exit(void)
{
i2c_del_driver(&mpu6050_driver);
}
module_init(mpu6050_init);
module_exit(mpu6050_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("liqinghua");
然后完善设备树匹配列表和i2c驱动结构体结构体。结构体内部相关函数未声明。传统和设备树匹配列表必须同时存在，不然无法进入probe函数。
/* 传统匹配方式ID列表 */
static const struct i2c_device_id mpu6050_id[] = {
{"alientek,mpu6050", 0},
{}
};
/* 设备树匹配列表 */
static const struct of_device_id mpu6050_of_match[] = {
{ .compatible = "alientek,mpu6050" },
{ /* Sentinel */ }
};
/* i2c驱动结构体 */
static struct i2c_driver mpu6050_driver = {
.probe = mpu6050_probe,
.remove = mpu6050_remove,
.driver = {
.owner = THIS_MODULE,
.name = "mpu6050",
.of_match_table = mpu6050_of_match,
},
.id_table = mpu6050_id,
};
然后完善probe和remove函数，这里主要是注册设备，以及删除设备
#define MPU_DEV_MAJOR 0
#define MPU_DEV_NAME "mpu6050"
#define MPU_DEV_CLASS_NAME "mpu6050_class"
#define MPU_DEV_NODE_NAME "mpu6050"
struct mpu6050_dev_t{
struct class *class;
struct device *device;
struct device_node *nd;
struct i2c_client *client;
int16_t acc[3];
int16_t gyro[3];
int16_t temp;
int major;
int minor;
};
struct mpu6050_dev_t mpu6050_dev;
static int mpu6050_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
int ret;
ret = register_chrdev(MPU_DEV_MAJOR, MPU_DEV_NAME, &mpu_drv_fops);
if(ret < 0){
printk("hello driver register failed\r\n");
return ret;
}
if(0 == MPU_DEV_MAJOR)
{
mpu6050_dev.major = ret;
}else
{
mpu6050_dev.major = MPU_DEV_MAJOR;
}
printk("led.major = %d\r\n",mpu6050_dev.major);
//创建类
mpu6050_dev.class = class_create(THIS_MODULE, MPU_DEV_CLASS_NAME);
if (IS_ERR(mpu6050_dev.class)) {
return PTR_ERR(mpu6050_dev.class);
}
//创建设备
mpu6050_dev.device = device_create(lempu6050_devd.class, NULL, MKDEV(mpu6050_dev.major, 0), NULL, MPU_DEV_NODE_NAME);
if (IS_ERR(mpu6050_dev.device)) {
return PTR_ERR(mpu6050_dev.device);
}
mpu6050_dev.client = client;
return 0;
}
static int mpu6050_remove(struct i2c_client *client)
{
unregister_chrdev(mpu6050_dev.major, MPU_DEV_NAME);
//删除类、删除设备
device_destroy(mpu6050_dev.class, MKDEV(mpu6050_dev.major, 0));
class_destroy(mpu6050_dev.class);
return 0;
}
然后编写文件操作函数
static int mpu6050_open(struct inode *inode, struct file *filp)
{
filp->private_data = &mpu6050_dev;
return 0;
}
static ssize_t mpu6050_read(struct file *filp, char __user *buf, size_t cnt, loff_t *off)
{
int16_t data[7];
long err = 0;
struct mpu6050_dev_t *dev = (struct mpu6050_dev_t *)filp->private_data;
mpu6050_read_data(dev);
data[0] = dev->acc[0];
data[1] = dev->acc[1];
data[2] = dev->acc[2];
data[3] = dev->gyro[0];
data[4] = dev->gyro[1];
data[5] = dev->gyro[2];
data[6] = dev->temp;
err = copy_to_user(buf, data, sizeof(data));
return 0;
}
static int mpu6050_release(struct inode *inode, struct file *filp)
{
return 0;
}
/* mpu6050操作函数 */
static const struct file_operations mpu_drv_fops = {
.owner = THIS_MODULE,
.open = mpu6050_open,
.read = mpu6050_read,
.release = mpu6050_release,
};
编写i2c的write和read函数
static int mpu6050_read_regs(struct mpu6050_dev_t *dev, u8 reg, void *val, int len)
{
int ret;
struct i2c_msg msg[2];
struct i2c_client *client = (struct i2c_client *)dev->client;
/* msg[0]为发送要读取的首地址 */
msg[0].addr = client->addr; /* mpu6050地址 */
msg[0].flags = 0; /* 标记为发送数据 */
msg[0].buf = ® /* 读取的首地址 */
msg[0].len = 1; /* reg长度*/
/* msg[1]读取数据 */
msg[1].addr = client->addr; /* mpu6050地址 */
msg[1].flags = I2C_M_RD; /* 标记为读取数据*/
msg[1].buf = val; /* 读取数据缓冲区 */
msg[1].len = len; /* 要读取的数据长度*/
ret = i2c_transfer(client->adapter, msg, 2);
if(ret == 2) {
ret = 0;
} else {
printk("i2c rd failed=%d reg=%06x len=%d\n",ret, reg, len);
ret = -EREMOTEIO;
}
return ret;
}
static s32 mpu6050_write_regs(struct mpu6050_dev_t *dev, u8 reg, u8 *buf, u8 len)
{
u8 b[256];
struct i2c_msg msg;
struct i2c_client *client = (struct i2c_client *)dev->private_data;
b[0] = reg; /* 寄存器首地址 */
memcpy(&b[1],buf,len); /* 将要写入的数据拷贝到数组b里面 */
msg.addr = client->addr; /* mpu6050地址 */
msg.flags = 0; /* 标记为写数据 */
msg.buf = b; /* 要写入的数据缓冲区 */
msg.len = len + 1; /* 要写入的数据长度 */
return i2c_transfer(client->adapter, &msg, 1);
}
然后就是关于mpu6050的初始化和读取代码了，这一部分，大部分是移植的正点原子的代码
//设置陀螺仪传感器满量程范围
//fsr:0,±250dps;1,±500dps;2,±1000dps;3,±2000dps
//返回值:0,设置成功
// 其他,设置失败
uint8_t MPU_Set_Gyro_Fsr(uint8_t fsr)
{
uint8_t fsr_temp;
fsr_temp = (fsr<<3)|3;
return mpu6050_write_regs(&mpu6050_dev,MPU_GYRO_CFG_REG,&fsr_temp,1);//设置陀螺仪满量程范围
}
//设置加速度传感器满量程范围
//fsr:0,±2g;1,±4g;2,±8g;3,±16g
//返回值:0,设置成功
// 其他,设置失败
uint8_t MPU_Set_Accel_Fsr(uint8_t fsr)
{
uint8_t fsr_temp;
fsr_temp = (fsr<<3);
return mpu6050_write_regs(&mpu6050_dev,MPU_ACCEL_CFG_REG,&fsr_temp,1);//设置加速度传感器满量程范围
}
//设置数字低通滤波器
//lpf:数字低通滤波频率(Hz)
//返回值:0,设置成功
// 其他,设置失败
uint8_t MPU_Set_LPF(uint16_t lpf)
{
uint8_t data=0;
if(lpf>=188)data=1;
else if(lpf>=98)data=2;
else if(lpf>=42)data=3;
else if(lpf>=20)data=4;
else if(lpf>=10)data=5;
else data=6;
return mpu6050_write_regs(&mpu6050_dev,MPU_CFG_REG,&data,1);//设置数字低通滤波器
}
//设置采样率(假定Fs=1KHz)
//rate:4~1000(Hz)
//返回值:0,设置成功
// 其他,设置失败
uint8_t MPU_Set_Rate(uint16_t rate)
{
uint8_t data;
if(rate>1000)rate=1000;
if(rate<4)rate=4;
data=1000/rate-1;
mpu6050_write_regs(&mpu6050_dev,MPU_SAMPLE_RATE_REG,&data,1); //设置数字低通滤波器
return MPU_Set_LPF(rate/2); //自动设置LPF为采样率的一半
}
static uint8_t MPU_Write_Byte(uint8_t reg,uint8_t data)
{
return mpu6050_write_regs(&mpu6050_dev,reg,&data,1);
}
static uint8_t MPU_Read_Byte(uint8_t reg)
{
uint8_t read_data;
mpu6050_read_regs(&mpu6050_dev,reg,&read_data,1);
return read_data;
}
//初始化
uint8_t MPU_Init(void)
{
uint8_t res=0;
MPU_Write_Byte(MPU_PWR_MGMT1_REG,0X80);//复位MPU6050
mdelay(100); //延时100ms
MPU_Write_Byte(MPU_PWR_MGMT1_REG,0X00);//唤醒MPU0650
MPU_Set_Gyro_Fsr(3); //陀螺仪传感器,±2000dps
MPU_Set_Accel_Fsr(0); //加速度传感器,±2g
MPU_Set_Rate(200); //设置采样率200Hz
MPU_Write_Byte(MPU_INT_EN_REG,0X00); //数据中断
MPU_Write_Byte(MPU_USER_CTRL_REG,0X00);//I2C主模式关闭
MPU_Write_Byte(MPU_FIFO_EN_REG,0X00); //关闭FIFO
MPU_Write_Byte(MPU_INTBP_CFG_REG,0X00);//选择中断电平，逻辑电平为0 50us高 查询立即自动清除
res=MPU_Read_Byte(MPU_DEVICE_ID_REG); //读取MPU6500的ID
if(res==0X68) //器件ID正确
{
MPU_Write_Byte(MPU_PWR_MGMT1_REG,0X01); //设置CLKSEL,PLL X轴为参考
MPU_Write_Byte(MPU_PWR_MGMT2_REG,0X00); //加速度与陀螺仪都工作
MPU_Set_Rate(200); //设置采样率为200Hz
} else return 1;
return 0;
}
void mpu6050_read_data(struct mpu6050_dev_t *dev)
{
uint8_t buf[6];
mpu6050_read_regs(dev,MPU_GYRO_XOUTH_REG,buf,6);
dev->gyro[0]=(((uint16_t)buf[0]<<8)|buf[1]);
dev->gyro[1]=(((uint16_t)buf[2]<<8)|buf[3]);
dev->gyro[2]=(((uint16_t)buf[4]<<8)|buf[5]);
mpu6050_read_regs(dev,MPU_ACCEL_XOUTH_REG,buf,6);
dev->acc[0]=(((uint16_t)buf[0]<<8)|buf[1]);
dev->acc[1]=(((uint16_t)buf[2]<<8)|buf[3]);
dev->acc[2]=(((uint16_t)buf[4]<<8)|buf[5]);
}
发现一个问题，我在使用float的时候交叉编译器说不支持，不知道为什么，后面解决
应用测试程序¶
#include "stdio.h"
#include "unistd.h"
#include "sys/types.h"
#include "sys/stat.h"
#include "sys/ioctl.h"
#include "fcntl.h"
#include "stdlib.h"
#include "string.h"
#include <poll.h>
#include <sys/select.h>
#include <sys/time.h>
#include <signal.h>
#include <fcntl.h>
/*
* @description : main主程序
* @param - argc : argv数组元素个数
* @param - argv : 具体参数
* @return : 0 成功;其他 失败
*/
int main(int argc, char *argv[])
{
int fd;
char *filename;
int16_t databuf[7];
int16_t gyro_x_adc, gyro_y_adc, gyro_z_adc;
int16_t accel_x_adc, accel_y_adc, accel_z_adc;
int16_t temp_adc;
int ret = 0;
if (argc != 2) {
printf("Error Usage!\r\n");
return -1;
}
filename = argv[1];
fd = open(filename, O_RDWR);
if(fd < 0) {
printf("can't open file %s\r\n", filename);
return -1;
}
while (1) {
ret = read(fd, databuf, sizeof(databuf));
if(ret == 0) { /* 数据读取成功 */
accel_x_adc = databuf[0];
accel_y_adc = databuf[1];
accel_z_adc = databuf[2];
gyro_x_adc = databuf[3];
gyro_y_adc = databuf[4];
gyro_z_adc = databuf[5];
temp_adc = databuf[6];
// These are the raw numbers from the chip, so will need tweaking to be really useful.
// See the datasheet for more information
printf("Acc. X = %d, Y = %d, Z = %d\n", accel_x_adc, accel_y_adc, accel_z_adc);
printf("Gyro. X = %d, Y = %d, Z = %d\n", gyro_x_adc, gyro_y_adc, gyro_z_adc);
// Temperature is simple so use the datasheet calculation to get deg C.
// Note this is chip temperature.
printf("Temp. = %f\n", (temp_adc / 340.0) + 36.53);
}
usleep(1000000); /*1000ms */
}
close(fd); /* 关闭文件 */
return 0;
}