STM32MP157 | 基于 Linux I2C 驱动读取si7006-A20温湿度传感器

一、si7006-A20

1.si7006的常用寄存器列表如下：

2. 开发板原理图

二、 添加设备树的节点

1.设置引脚

首先设置I2C1引脚的复用功能，找到 pinctrl_i2c1 节点：

vi stm32mp15-pinctrl.dtsi

2. 找出控制器的设备树

stm32mp151.dtsi

i2c1: i2c@40012000 {compatible = "st,stm32mp15-i2c"; //这个是和i2c控制器驱动完成匹配reg = <0x40012000 0x400>;        //控制器的地址和长度interrupt-names = "event", "error";                                                                   interrupts-extended = <&exti 21 IRQ_TYPE_LEVEL_HIGH>,<&intc GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;clocks = <&rcc I2C1_K>;resets = <&rcc I2C1_R>;#address-cells = <1>;   //修饰子节点地址的个数#size-cells = <0>;      //修饰子节点长度的个数dmas = <&dmamux1 33 0x400 0x80000001>,//dam内存直取，可以把数据直接从一个地址搬移到另一个地址<&dmamux1 34 0x400 0x80000001>;dma-names = "rx", "tx";power-domains = <&pd_core>;st,syscfg-fmp = <&syscfg 0x4 0x1>;wakeup-source;i2c-analog-filter;status = "disabled";  //控制器没有使能
};

3. 根据内核帮助文档编写自己的设备树

/home/linux/linux-5.10.61/Documentation/devicetree/bindings/i2c/

&i2c1{//第0个成员工作状态，第1个休眠状态pinctrl-names = "default", "sleep";//这个就是列表pinctrl-0 = <&i2c1_pins_b>;//pinctrl-0 代表列表中第0个成员//i2c1_pins_b代表管脚复用pinctrl-1 = <&i2c1_sleep_pins_b>;//pinctrl-1 代表列表中第1个成员i2c-scl-rising-time-ns = <100>;//上升沿时间毫秒i2c-scl-falling-time-ns = <7>;//下降沿时间status = "okay";    //使能                                                                                          /delete-property/dmas;      //删除dma属性/delete-property/dma-names;si7006@40{ 	//添加的设备树节点compatible = "st,si7006";reg = <0x40>;//从机地址};
};

4. 重新编译设备树

make dtbs

重启开发板

安装驱动

三. 编写si7006设备驱动

1.先搭个I2C设备驱动框架

#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>int si7006_probe(struct i2c_client *client, const struct i2c_device_id *id)
{printk("%s:%d\n", __func__, __LINE__);return 0;
}int si7006_remove(struct i2c_client *client)
{printk("%s:%d\n", __func__, __LINE__);return 0;
}//通过设备树的形式匹配进入probe函数
const struct of_device_id oftable[] = {{.compatible = "st,si7006",},{},
};//支持热插拔
MODULE_DEVICE_TABLE_TABLE(of, oftable);struct i2c_driver si7006 = {.probe = si7006_probe,.remove = si7006_remove,.driver = {.name = "hello",.of_match_table = oftable,}
};module_i2c_driver(si7006);
MODULE_LICENSE("GPL");

写个Makefile编译一下：

ifeq ($(arch),arm)
KERNELDIR :=/home/linux/linux-5.10.61
CROSS_COMPILE ?=arm-linux-gnueabihf-
else 
KERNELDIR :=/lib/modules/$(shell uname -r)/build
CROSS_COMPILE ?=
endif modname ?=
PWD :=$(shell pwd)CC :=$(CROSS_COMPILE)gccall:make -C $(KERNELDIR) M=$(PWD) modules# $(CC) test.c -o test
clean:make -C $(KERNELDIR) M=$(PWD) clean# rm testinstall:cp *.ko ~/nfs/rootfs/# cp test ~/nfs/rootfs/help:echo "make arch = arm or x86 modname= dirvers file name"obj-m:=$(modname).o

linux@ubuntu:~/linu/driver/csdn/si7006$ make arch=arm modname=si7006

2. 再写字符设备驱动框架

#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#define CNAME "si7006"dev_t devno;
int major = 0;
int minor = 0;
int count = 1;
struct cdev *cdev;
struct class *cls;
struct device *dev;
int si7006_open(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}long si7006_ioctl(struct file *file, unsigned int cmd, unsigned long which)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}
int si7006_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}
struct file_operations fops = {.open = si7006_open,.unlocked_ioctl = si7006_ioctl,.release = si7006_close,
};
int si7006_probe(struct i2c_client *client, const struct i2c_device_id *id)
{int ret;// 1.分配对象cdev = cdev_alloc();if (cdev == NULL){printk("alloc memory failed\n");ret = -ENOMEM;goto ERR1;}// 2.初始化对象cdev_init(cdev, &fops);// 3.申请设备号if (major > 0){	//静态申请ret = register_chrdev_region(MKDEV(major, minor), count, CNAME);if (ret != 0){printk("static:alloc device number failed!\n");goto ERR2;}}else if (major == 0){	//动态申请ret = alloc_chrdev_region(&devno, 0, 1, CNAME);if (ret != 0){printk("dynamic:alloc device number failed!\n");goto ERR2;}major = MAJOR(devno);minor = MINOR(devno);}// 4.注册对象ret = cdev_add(cdev, MKDEV(major, minor), count);if (ret){printk("add cdev failed\n");goto ERR3;}// 5.向上层提交目录的信息cls = class_create(THIS_MODULE, "hello");if (IS_ERR(cls)){printk("create class failed\n");ret = PTR_ERR(cls);goto ERR4;}// 6.向上层提交设备的信息dev = device_create(cls, NULL, MKDEV(major, minor), NULL, CNAME);if (IS_ERR(dev)){printk("create device failed\n");ret = PTR_ERR(dev);goto ERR5;}return 0;
ERR5:class_destroy(cls);
ERR4:cdev_del(cdev);
ERR3:unregister_chrdev_region(MKDEV(major, minor), count);
ERR2:kfree(cdev);
ERR1:return ret;
}
int si7006_remove(struct i2c_client *client)
{device_destroy(cls,MKDEV(major,minor));class_destroy(cls);cdev_del(cdev);unregister_chrdev_region(MKDEV(major, minor), count);kfree(cdev);printk("%s:%d\n", __func__, __LINE__);return 0;
}
}//通过设备树的形式匹配进入probe函数
const struct of_device_id oftable[] = {{.compatible = "st,si7006",},{},
};
//支持热插拔
MODULE_DEVICE_TABLE(of, oftable);struct i2c_driver si7006 = {.probe = si7006_probe,.remove = si7006_remove,.driver = {.name = "hello",.of_match_table = oftable,}};module_i2c_driver(si7006);
MODULE_LICENSE("GPL");

3.封装i2c操作代码

(1) 全局变量中添加 i2c_client 成员：

struct i2c_client *gclient;

（2）在 si7006_probe中获取i2c_client结构体

int si7006_probe(struct i2c_client *client, const struct i2c_device_id *id)
{gclient = client; 
}

(3)si7006读取温湿度的顺序如下

int i2c_read_tmp_hum(unsigned char reg)
{int ret;unsigned char r_buf[] = { reg };unsigned short data;// 1.封装消息struct i2c_msg r_msg[] = {[0] = {.addr = gclient->addr,.flags = 0,	.len = 1,.buf = r_buf,},[1] = {.addr = gclient->addr,.flags = 1,.len = 2,.buf =  (__u8 *)&data,//这里返回的数据是两位的//这里先返回的是高8位u也就是地址的地位存储着数据的高8位，//所以要把他调转回来arm是小端存储地址低位存储数据地位},};// 2发送消息ret = i2c_transfer(gclient->adapter, r_msg, ARRAY_SIZE(r_msg));if (ret != ARRAY_SIZE(r_msg)) {printk("i2c read serial or firmware error\n");return -EAGAIN;}data = data >> 8 | data << 8;return data;
}

3.字符设备驱动的实现

ioctl头文件引入

#include <linux/ioctl.h>
#include "si7006.h"

添加头文件，封装命令码

si7006.h

#ifndef __SI7006_H__
#define __SI7006_H__#define GET_SI7006_TMP _IOR('r',0,int)
#define GET_SI7006_HUM _IOR('r',1,int)#define GET_CMD_SIZE(cmd)  ((cmd>>16)&0x3fff)
#define TMP_ADDR 0xe3	//温度寄存器地址
#define HUM_ADDR 0xe5	//湿度寄存器地址
#endif

open

int si7006_open(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}

ioctl

long si7006_ioctl(struct file *file, unsigned int cmd, unsigned long args)
{int ret,data;switch (cmd) {case GET_SI7006_TMP:data = i2c_read_tmp_hum(TMP_ADDR);ret = copy_to_user((void *)args,&data,GET_CMD_SIZE(GET_SI7006_TMP));if(ret){printk("copy data to user error\n");return -EIO;}break;case GET_SI7006_HUM:data = i2c_read_tmp_hum(HUM_ADDR);ret = copy_to_user((void *)args,&data,GET_CMD_SIZE(GET_SI7006_HUM));if(ret){printk("copy data to user error\n");return -EIO;}break;}printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}

close

int si7006_close(struct inode *inode, struct file *file)
{printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);return 0;
}

四、测试驱动模块

1.加载驱动,查看驱动

2.编写app测试程序

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "si7006.h"#define PRINT_ERR(msg) \do                 \{                  \perror(msg);   \return -1;     \} while (0)int main(int argc, const char* argv[])
{int fd;int tmp, hum;float rtmp, rhum;if ((fd = open("/dev/si7006", O_RDWR)) == -1)PRINT_ERR("open error");while (1) {ioctl(fd, GET_SI7006_TMP, &tmp);ioctl(fd, GET_SI7006_HUM, &hum);rtmp = 175.72 * tmp / 65536 - 46.85;rhum = 125 * hum / 65536 - 6;printf("tmp = %.2f,hum=%.2f\n", rtmp, rhum);sleep(1);}close(fd);return 0;
}

成功读取读到温湿度