mtk7688之openwrt平台下温湿度传感器应用
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mtk7688之openwrt平台下温湿度传感器应用
我之前测试了DS18B20和DHT11传感器，都测试通过，这篇主要讲解如何实现DHT11传感器在openwrt平台上的应用。
DHT11是一款有已校准数字信号输出的温湿度传感器。 其精度湿度+-5%RH， 温度+-2℃，量程湿度20-90%RH， 温度0~50℃，由于mtk7688基本引脚都复用了，板子也没引出什么IO引脚，正好我的板子引出了UART1的引脚排针，所以我使用了TX1引脚来作为DHT11的IO交互引脚，IO的配置方法之前我的几篇已经分析了很详细，就不讲了，我把重点的内核驱动需要改动的地方红色标注了，linux的内核驱动就是这样，基本都是依葫芦画瓢，90%的代码基本不需要改动，就是改动些相关具体的驱动代码，其他的传感器配置可以参考这篇来。
应用测试程序
#include #include #include #include #include #include #include int main(int argc, char **argv) { int fd; unsigned int dht11 = 0; unsigned int humi,temp; //打开温度传感器驱动模块 fd = open("/dev/dht11", O_RDWR | O_NONBLOCK); if (fd < 0) { printf("can't open /dev/dht11\n"); return -1; } read(fd, &dht11, sizeof(dht11)); temp = dht11>>8; humi = dht11 &0x000000ff; printf("the current temperature is: %d\n",temp); printf("the current humidity is: %d\n",humi); close(fd); return 0; } DHT11内核驱动代码： /***************************** * * 驱动程序模板 * 版本：V1 * 使用方法(末行模式下)： * :%s/dht11/"你的驱动名称"/g * *******************************/ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //配置连接温度传感器的引脚 #define DHT11_L *GPIO45_DATA &= ~(1<<13) //低电平 #define DHT11_H *GPIO45_DATA |= (1<<13) //高电平 #define DHT11_OUT *GPIO45_DIR |= (1<<13) //输出 #define DHT11_IN *GPIO45_DIR &= ~(1<<13) //输入 #define DHT11_STA ((*GPIO45_DATA>>13) & 0x01) //寄存器定义 volatile unsigned long *GPIO45_MODE; volatile unsigned long *GPIO45_DIR; volatile unsigned long *GPIO45_DATA; /**************** 基本定义 **********************/ //初始化函数必要资源定义 //用于初始化函数当中 //device number; dev_t dev_num; //struct dev struct cdev dht11_cdev; //auto "mknode /dev/dht11 c dev_num minor_num" struct class *dht11_class = NULL; struct device *dht11_device = NULL; /******************** dht11有关的函数 ****************************/ //从dht11中读取一个字节 static unsigned char read_byte(void) { unsigned char r_val = 0; unsigned char t_count = 0; //计时器，防止超时； unsigned char i; for(i = 0 ; i < 8 ; i++) { t_count = 0; while(!DHT11_STA) { udelay(1); t_count++; if(t_count>250) { printk("read_byte error1\n"); return 100; } } t_count = 0; udelay(32); if(DHT11_STA == 1) { r_val <<= 1; r_val |= 1; } else { r_val <<= 1; continue; } while( DHT11_STA == 1 ) { udelay(2); t_count++; if(t_count>250) { printk("read_byte error2\n"); return 100; } } } return r_val; } //从dht11中读出数据 static unsigned int read_dht11(void) { unsigned char t_count = 0; //计时器； unsigned int dht11 = 0; unsigned char h_i = 0 , h_f = 0; unsigned char t_i = 0 , t_f = 0; unsigned char check_sum = 0; DHT11_OUT; DHT11_L; mdelay(30); //>18ms; DHT11_H; udelay(30); DHT11_IN; while(DHT11_STA == 1) { udelay(1); t_count++; if(t_count > 50) { printk("device error: dht11!\n"); return 0; } } t_count = 0; while(!DHT11_STA) { udelay(1); t_count++; if(t_count > 250) { printk("read_dht11 error1\n"); return 0; } } t_count = 0; udelay(50); while(DHT11_STA) { udelay(1); t_count++; if(t_count > 250) { printk("read_dht11 error2\n"); return 0; } } h_i = read_byte(); h_f = read_byte(); t_i = read_byte(); t_f = read_byte(); check_sum = read_byte(); if(check_sum == (h_i+h_f+t_i+t_f) || (h_i!=100 && t_i != 100)) { dht11 = t_i; dht11 <<= 8; dht11 += h_i; } else { dht11 = 0; printk("read_dht11 error3\n"); } return dht11; } /**********************************************************************/ /**************** 结构体 file_operations 成员函数 *****************/ //open static int dht11_open(struct inode *inode, struct file *file) { printk("dht11 drive open...\n"); DHT11_OUT; DHT11_H; return 0; } //close static int dht11_close(struct inode *inode , struct file *file) { return 0; } //read static ssize_t dht11_read(struct file *file, char __user *buffer, size_t len, loff_t *pos) { unsigned int dht11; printk("dht11 drive read...\n"); dht11 = read_dht11(); copy_to_user(buffer, &dht11, 4); return 4; } /***************** 结构体： file_operations ************************/ //struct static const struct file_operations dht11_fops = { .owner = THIS_MODULE, .open = dht11_open, .release = dht11_close, .read = dht11_read, }; /************* functions: init , exit*******************/ //条件值变量，用于指示资源是否正常使用 unsigned char init_flag = 0; unsigned char add_code_flag = 0; //init static __init int dht11_init(void) { int ret_v = 0; printk("dht11 drive init...\n"); //函数alloc_chrdev_region主要参数说明： //参数2： 次设备号 //参数3： 创建多少个设备 if( ( ret_v = alloc_chrdev_region(&dev_num,0,1,"dht11") ) < 0 ) { goto dev_reg_error; } init_flag = 1; //标示设备创建成功； printk("The drive info of dht11:\nmajor: %d\nminor: %d\n", MAJOR(dev_num),MINOR(dev_num)); cdev_init(&dht11_cdev,&dht11_fops); if( (ret_v = cdev_add(&dht11_cdev,dev_num,1)) != 0 ) { goto cdev_add_error; } dht11_class = class_create(THIS_MODULE,"dht11"); if( IS_ERR(dht11_class) ) { goto class_c_error; } dht11_device = device_create(dht11_class,NULL,dev_num,NULL,"dht11"); if( IS_ERR(dht11_device) ) { goto device_c_error; } printk("auto mknod success!\n"); //------------ 请在此添加您的初始化程序 --------------// GPIO45_MODE = (volatile unsigned long *)ioremap(0x10000060, 4); GPIO45_DATA = (volatile unsigned long *)ioremap(0x10000624, 4); GPIO45_DIR = (volatile unsigned long *)ioremap(0x10000604, 4); //如果需要做错误处理，请：goto dht11_error; *GPIO45_MODE |= (1u<<24); *GPIO45_DIR |= (1u<<13); add_code_flag = 1; //---------------------- END ---------------------------// goto init_success; dev_reg_error: printk("alloc_chrdev_region failed\n"); return ret_v; cdev_add_error: printk("cdev_add failed\n"); unregister_chrdev_region(dev_num, 1); init_flag = 0; return ret_v; class_c_error: printk("class_create failed\n"); cdev_del(&dht11_cdev); unregister_chrdev_region(dev_num, 1); init_flag = 0; return PTR_ERR(dht11_class); device_c_error: printk("device_create failed\n"); cdev_del(&dht11_cdev); unregister_chrdev_region(dev_num, 1); class_destroy(dht11_class); init_flag = 0; return PTR_ERR(dht11_device); //------------------ 请在此添加您的错误处理内容 ----------------// dht11_error: add_code_flag = 0; return -1; //-------------------- END -------------------// init_success: printk("dht11 init success!\n"); return 0; } //exit static __exit void dht11_exit(void) { printk("dht11 drive exit...\n"); if(add_code_flag == 1) { //---------- 请在这里释放您的程序占有的资源 ---------// printk("free your resources...\n"); iounmap(GPIO45_MODE); iounmap(GPIO45_DATA); iounmap(GPIO45_DIR); printk("free finish\n"); //---------------------- END -------------------// } if(init_flag == 1) { //释放初始化使用到的资源; cdev_del(&dht11_cdev); unregister_chrdev_region(dev_num, 1); device_unregister(dht11_device); class_destroy(dht11_class); } } /**************** module operations**********************/ //module loading module_init(dht11_init); module_exit(dht11_exit); //some infomation MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("from Jafy"); MODULE_DESCRIPTION("dht11 drive"); /********************* The End ***************************/ 运行结果如下: root@Widora:/etc# dht11_app [ 5105.220000] dht11 drive open... [ 5105.220000] dht11 drive read... the current temperature is: 29 the current humidity is: 34
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