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【驱动篇】龙芯LS2K0300之单总线驱动

news 来源：原创 2024/9/29 15:20:48

实验过程

实验目的： 在龙芯开发板上面使用单总线驱动DS18B20温度传感器

① 根据原理图连接DS18B20模块

② 将i2c0引脚的功能复用为GPIO

③ 注册字符设备，按照DS18B20的读写时序编写读写驱动接口

④ 编写测试用例解析传感器的数值

原理图

将板子上面的GPIO48连接传感器的DAT引脚，其余引脚连接如下

在这里插入图片描述

然后记得在设备树中把i2c0部分代码注释掉，将PIN16复用为GPIO48

驱动代码

定义相关传感器设备结构体

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/errno.h>#define DS18B20_DEV_NUM			1		  
#define DS18B20_DEV		        "ds18b20"	
#define DS18B20_GPIO            48
#define DS18B20_DQ_OUT(x)       gpio_direction_output(ds18b20.gpio, x)
#define DS18B20_DQ_IN           ds18b20_get_io()struct ds18b20_dev {dev_t dev_id;		struct cdev cdev;	struct class *class;	struct device *device;	int major;			int minor;	int gpio;				unsigned char data[2]; struct timer_list timer;	struct work_struct work;
};struct ds18b20_dev ds18b20;

传感器数据读写交互

static int ds18b20_get_io(void)
{gpio_direction_input(ds18b20.gpio);return gpio_get_value(ds18b20.gpio); 
}static void ds18b20_reset(void)
{DS18B20_DQ_OUT(0);  /* 拉低DQ,复位 */udelay(750);      /* 拉低750us */DS18B20_DQ_OUT(1);  /* DQ=1, 释放复位 */udelay(15);       /* 延迟15US */
}uint8_t ds18b20_check(void)
{uint8_t retry = 0;uint8_t rval = 0;while (DS18B20_DQ_IN && retry < 200)    /* 等待DQ变低, 等待200us */{retry++;udelay(1);}if (retry >= 200){rval = 1;}else{retry = 0;while (!DS18B20_DQ_IN && retry < 240)   /* 等待DQ变高, 等待240us */{retry++;udelay(1);}if (retry >= 240) rval = 1;}return rval;
}static uint8_t ds18b20_read_bit(void)
{uint8_t data = 0;DS18B20_DQ_OUT(0);udelay(2);DS18B20_DQ_OUT(1);udelay(12);if (DS18B20_DQ_IN){data = 1;}udelay(50);return data;
}static uint8_t ds18b20_read_byte(void)
{uint8_t i, b, data = 0;for (i = 0; i < 8; i++){b = ds18b20_read_bit(); /* DS18B20先输出低位数据 ,高位数据后输出 */data |= b << i;         /* 填充data的每一位 */}return data;
}static void ds18b20_write_byte(uint8_t data)
{uint8_t j;for (j = 1; j <= 8; j++){if (data & 0x01){DS18B20_DQ_OUT(0);  /*  Write 1 */udelay(2);DS18B20_DQ_OUT(1);udelay(60);}else{DS18B20_DQ_OUT(0);  /*  Write 0 */udelay(60);DS18B20_DQ_OUT(1);udelay(2);}data >>= 1;             /* 右移,获取高一位数据 */}
}static void ds18b20_start(void)
{ds18b20_reset();ds18b20_check();ds18b20_write_byte(0xcc);   /*  skip rom */ds18b20_write_byte(0x44);   /*  convert */
}static int ds18b20_init(void)
{gpio_direction_output(ds18b20.gpio, 0);ds18b20_reset();return ds18b20_check();	
}

注册字符设备，绑定相关回调函数

static int ds18b20_open(struct inode *inode, struct file *filp)
{return 0;
}static ssize_t ds18b20_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt) 
{int ret;ret = copy_to_user(buf, &ds18b20.data[0], 2);if(ret)return -ENOMEM;return ret;
}static struct file_operations ds18b20_fops = {.owner	= THIS_MODULE,.open = ds18b20_open,.read	= ds18b20_read,
};static void ds18b20_work_callback(struct work_struct *work)
{ds18b20_start();                            /*  ds1820 start convert */ds18b20_reset();ds18b20_check();ds18b20_write_byte(0xcc);                   /*  skip rom */ds18b20_write_byte(0xbe);                   /*  convert */ds18b20.data[0] = ds18b20_read_byte();      /*  LSB */ds18b20.data[1] = ds18b20_read_byte();      /*  MSB */
}static void ds18b20_timer_callback(struct timer_list *arg)
{schedule_work(&ds18b20.work);	mod_timer(&ds18b20.timer, jiffies + (1000 * HZ/1000));	
}static int ds18b20_module_init(void)
{int ret = 0;ds18b20.gpio = DS18B20_GPIO;if (!gpio_is_valid(ds18b20.gpio)) {return -EINVAL;}ret = gpio_request(ds18b20.gpio, "DS18B20-GPIO");if (ret) {printk(KERN_ERR "ds18b20 : Failed to request gpio\n");return ret;}ds18b20_init();if (ds18b20.major) {		ds18b20.dev_id = MKDEV(ds18b20.major, 0);ret = register_chrdev_region(ds18b20.dev_id, DS18B20_DEV_NUM, DS18B20_DEV);if(ret < 0) {pr_err("cannot register %s char driver [ret=%d]\n", DS18B20_DEV, DS18B20_DEV_NUM);goto free_gpio;}} else {					ret = alloc_chrdev_region(&ds18b20.dev_id, 0, DS18B20_DEV_NUM, DS18B20_DEV);if(ret < 0) {pr_err("%s Couldn't alloc_chrdev_region, ret=%d\r\n", DS18B20_DEV, ret);goto free_gpio;}ds18b20.major = MAJOR(ds18b20.dev_id);	ds18b20.minor = MINOR(ds18b20.dev_id);	}ds18b20.cdev.owner = THIS_MODULE;cdev_init(&ds18b20.cdev, &ds18b20_fops);cdev_add(&ds18b20.cdev, ds18b20.dev_id, DS18B20_DEV_NUM);if(ret < 0)goto del_unregister;ds18b20.class = class_create(THIS_MODULE, DS18B20_DEV);if (IS_ERR(ds18b20.class)) {goto del_cdev;}ds18b20.device = device_create(ds18b20.class, NULL, ds18b20.dev_id, NULL, DS18B20_DEV);if (IS_ERR(ds18b20.device)) {goto destroy_class;}timer_setup(&ds18b20.timer, ds18b20_timer_callback, 0);ds18b20.timer.expires=jiffies + msecs_to_jiffies(1000);add_timer(&ds18b20.timer);INIT_WORK(&ds18b20.work, ds18b20_work_callback);return 0;destroy_class:class_destroy(ds18b20.class);
del_cdev:cdev_del(&ds18b20.cdev);
del_unregister:unregister_chrdev_region(ds18b20.dev_id, DS18B20_DEV_NUM);
free_gpio:gpio_free(ds18b20.gpio);return -EIO;
}

整合代码

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/errno.h>#define DS18B20_DEV_NUM			1		  
#define DS18B20_DEV		        "ds18b20"	
#define DS18B20_GPIO            48	
#define DS18B20_DQ_OUT(x)       gpio_direction_output(ds18b20.gpio, x)
#define DS18B20_DQ_IN           ds18b20_get_io()struct ds18b20_dev {dev_t dev_id;		struct cdev cdev;	struct class *class;	struct device *device;	int major;			int minor;	int gpio;				unsigned char data[2]; struct timer_list timer;	struct work_struct work;
};struct ds18b20_dev ds18b20;static int ds18b20_get_io(void)
{gpio_direction_input(ds18b20.gpio);return gpio_get_value(ds18b20.gpio); 
}static void ds18b20_reset(void)
{DS18B20_DQ_OUT(0);  /* 拉低DQ,复位 */udelay(750);      /* 拉低750us */DS18B20_DQ_OUT(1);  /* DQ=1, 释放复位 */udelay(15);       /* 延迟15US */
}uint8_t ds18b20_check(void)
{uint8_t retry = 0;uint8_t rval = 0;while (DS18B20_DQ_IN && retry < 200)    /* 等待DQ变低, 等待200us */{retry++;udelay(1);}if (retry >= 200){rval = 1;}else{retry = 0;while (!DS18B20_DQ_IN && retry < 240)   /* 等待DQ变高, 等待240us */{retry++;udelay(1);}if (retry >= 240) rval = 1;}return rval;
}static uint8_t ds18b20_read_bit(void)
{uint8_t data = 0;DS18B20_DQ_OUT(0);udelay(2);DS18B20_DQ_OUT(1);udelay(12);if (DS18B20_DQ_IN){data = 1;}udelay(50);return data;
}static uint8_t ds18b20_read_byte(void)
{uint8_t i, b, data = 0;for (i = 0; i < 8; i++){b = ds18b20_read_bit(); /* DS18B20先输出低位数据 ,高位数据后输出 */data |= b << i;         /* 填充data的每一位 */}return data;
}static void ds18b20_write_byte(uint8_t data)
{uint8_t j;for (j = 1; j <= 8; j++){if (data & 0x01){DS18B20_DQ_OUT(0);  /*  Write 1 */udelay(2);DS18B20_DQ_OUT(1);udelay(60);}else{DS18B20_DQ_OUT(0);  /*  Write 0 */udelay(60);DS18B20_DQ_OUT(1);udelay(2);}data >>= 1;             /* 右移,获取高一位数据 */}
}static void ds18b20_start(void)
{ds18b20_reset();ds18b20_check();ds18b20_write_byte(0xcc);   /*  skip rom */ds18b20_write_byte(0x44);   /*  convert */
}static int ds18b20_init(void)
{gpio_direction_output(ds18b20.gpio, 0);ds18b20_reset();return ds18b20_check();	
}static int ds18b20_open(struct inode *inode, struct file *filp)
{return 0;
}static ssize_t ds18b20_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt) 
{int ret;ret = copy_to_user(buf, &ds18b20.data[0], 2);if(ret)return -ENOMEM;return ret;
}static struct file_operations ds18b20_fops = {.owner	= THIS_MODULE,.open = ds18b20_open,.read	= ds18b20_read,
};static void ds18b20_work_callback(struct work_struct *work)
{ds18b20_start();                            /*  ds1820 start convert */ds18b20_reset();ds18b20_check();ds18b20_write_byte(0xcc);                   /*  skip rom */ds18b20_write_byte(0xbe);                   /*  convert */ds18b20.data[0] = ds18b20_read_byte();      /*  LSB */ds18b20.data[1] = ds18b20_read_byte();      /*  MSB */
}static void ds18b20_timer_callback(struct timer_list *arg)
{schedule_work(&ds18b20.work);	mod_timer(&ds18b20.timer, jiffies + (1000 * HZ/1000));	
}static int ds18b20_module_init(void)
{int ret = 0;ds18b20.gpio = DS18B20_GPIO;if (!gpio_is_valid(ds18b20.gpio)) {return -EINVAL;}ret = gpio_request(ds18b20.gpio, "DS18B20-GPIO");if (ret) {printk(KERN_ERR "ds18b20 : Failed to request gpio\n");return ret;}ds18b20_init();if (ds18b20.major) {		ds18b20.dev_id = MKDEV(ds18b20.major, 0);ret = register_chrdev_region(ds18b20.dev_id, DS18B20_DEV_NUM, DS18B20_DEV);if(ret < 0) {pr_err("cannot register %s char driver [ret=%d]\n", DS18B20_DEV, DS18B20_DEV_NUM);goto free_gpio;}} else {					ret = alloc_chrdev_region(&ds18b20.dev_id, 0, DS18B20_DEV_NUM, DS18B20_DEV);if(ret < 0) {pr_err("%s Couldn't alloc_chrdev_region, ret=%d\r\n", DS18B20_DEV, ret);goto free_gpio;}ds18b20.major = MAJOR(ds18b20.dev_id);	ds18b20.minor = MINOR(ds18b20.dev_id);	}ds18b20.cdev.owner = THIS_MODULE;cdev_init(&ds18b20.cdev, &ds18b20_fops);cdev_add(&ds18b20.cdev, ds18b20.dev_id, DS18B20_DEV_NUM);if(ret < 0)goto del_unregister;ds18b20.class = class_create(THIS_MODULE, DS18B20_DEV);if (IS_ERR(ds18b20.class)) {goto del_cdev;}ds18b20.device = device_create(ds18b20.class, NULL, ds18b20.dev_id, NULL, DS18B20_DEV);if (IS_ERR(ds18b20.device)) {goto destroy_class;}timer_setup(&ds18b20.timer, ds18b20_timer_callback, 0);ds18b20.timer.expires=jiffies + msecs_to_jiffies(1000);add_timer(&ds18b20.timer);INIT_WORK(&ds18b20.work, ds18b20_work_callback);return 0;destroy_class:class_destroy(ds18b20.class);
del_cdev:cdev_del(&ds18b20.cdev);
del_unregister:unregister_chrdev_region(ds18b20.dev_id, DS18B20_DEV_NUM);
free_gpio:gpio_free(ds18b20.gpio);return -EIO;
}static void ds18b20_module_exit(void)
{cdev_del(&ds18b20.cdev);unregister_chrdev_region(ds18b20.dev_id, DS18B20_DEV_NUM); device_destroy(ds18b20.class, ds18b20.dev_id);class_destroy(ds18b20.class);del_timer(&ds18b20.timer);cancel_work_sync(&ds18b20.work);gpio_free(ds18b20.gpio); 
}module_init(ds18b20_module_init);
module_exit(ds18b20_module_exit);
MODULE_LICENSE("GPL");

Makefile文件

obj-m += ds18b20.o 
KDIR:=/home/asensing/loongson/linux-4.19
ARCH=loongarch 
CROSS_COMPILE=loongarch64-linux-gnu-
PWD?=$(shell pwd) 
all:make -C $(KDIR) M=$(PWD) modules

构建脚本

export PATH=$PATH:/home/asensing/loongson/loongson-gnu-toolchain-8.3-x86_64-loongarch64-linux-gnu-rc1.3-1/bin
make -j8
loongarch64-linux-gnu-gcc test.c -o test
FILE=$PWD/$(basename $PWD).ko
scp $FILE test root@192.168.137.216:/home/root

测试用例

#include "stdio.h"
#include "unistd.h"
#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "stdlib.h"
#include "string.h"#define DEV_NAME "/dev/ds18b20"int main()
{int fd, ret;unsigned char result[2];unsigned char TH, TL;short tmp = 0;float temperature;int flag = 0;fd = open(DEV_NAME, 0);if(fd < 0){printf("open %s device failed\n", DEV_NAME);exit(1);}elseprintf("Open %s success!\n", DEV_NAME);while(1){ret = read(fd, &result, sizeof(result)); if(ret == 0) {	/* 读取到数据 */TL = result[0];TH = result[1];if(TH > 7) {	/* 负数处理 */TH = ~TH;TL = ~TL;flag = 1;	/* 标记为负数 */}tmp = TH;tmp <<= 8;tmp += TL;if(flag == 1) {temperature = (float)(tmp+1) * 0.0625; /* 计算负数的温度 */temperature = -temperature;}else {temperature = (float)tmp *0.0625;	/* 计算正数的温度 */}            if(temperature < 125 && temperature > -55) {	/* 温度范围 */printf("Environment Temperature Now : %0.2f℃\n", temperature);}}flag = 0;sleep(1);}close(fd);	/* 关闭文件 */
}

实验效果

插入驱动后，使用测试用例实时读取环境温度值

在这里插入图片描述

广东太热，我要回非洲！

在这里插入图片描述

参考

以上驱动参考自RT-Thread的工程：rtt-psoc62/one-wire/ds18b20.c at main · hywing/rtt-psoc62 (github.com)

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