[问答]

如何去实现基于RK3399Pro的LED闪烁实验呢

问答对人有帮助，内容完整，我也想知道答案 0 原理图发光二极管与普通二极管一样是由一个PN结组成，也具有单向导电性。当给发光二极管加上正向电压后，从P区注入到N区的空穴和由N区注入到P区的电子，在PN结附近数微米内分别与N区的电子和P区的空穴复合，产生自发辐射的荧光。问题1：如何判断正负极？尺寸大的LED 在极片引脚附近做有一些标记，如切角、涂色、或引脚大小不一样，一般有标志的、引脚小的、短的一边是阴极（即负极），尺寸小的0805、0603封装的在底部有“T”字形或倒三角形符号“T”字一横的一边是正极；三角形符号的“边”靠近的极性正，“角”靠近的是负极。添加设备树在设备树 arch/arm64/boot/dts/rockchip/rk3399pro-toybrick-prop-linux.dts 中添加 gpio-led{ status = "okay"; compatible = "gpio-led"; gpio-led1 = <&gpio1 RK_PB0 GPIO_ACTIVE_LOW>; gpio-led2 = <&gpio1 RK_PA7 GPIO_ACTIVE_LOW>; }; 编写驱动程序设备节点 static const struct of_device_id of_gec_leder_match[] = { { .compatible = "gpio-led", }, //compatible 兼容属性名，需与设备树节点的属性一致 {}, }; static struct platform_driver gec3399_led_driver = { .driver = { .name ="gpio-led", .owner = THIS_MODULE, .of_match_table = of_gec_leder_match, //设备树设备匹配 }, .probe = gec3399_led_probe, //驱动探测 .remove = gec3399_led_remove, //驱动移除 }; 文件入口函数 static int gec3399_led_probe(struct platform_device pdev) { int ret; struct device_node led_node = pdev->dev.of_node; //第一步：获取GPIO引脚号 gpio_led1 = of_get_named_gpio(led_node,"gpio-led1", 0); //从设备树获取GPIO号 if (!gpio_is_valid(gpio_led1)) { printk("gpio-led1: %d is invalid ",gpio_led1); ret = -ENODEV; goto err_get_gpio1; } printk("gpio-led1 = %d ",gpio_led1); gpio_led2 = of_get_named_gpio(led_node,"gpio-led2", 0); //从设备树获取GPIO号 if (!gpio_is_valid(gpio_led2)) { printk("gpio-led2: %d is invalid ",gpio_led2); ret = -ENODEV; goto err_get_gpio1; } printk("gpio-led2 = %d ",gpio_led2); //第二步：申请GPIO引脚 gpio_free(gpio_led1); ret = gpio_request(gpio_led1,"GPIO_LED1"); //申请gpio_led引脚为GPIO模式 if(ret < 0){ printk("gpio_request gpio = GPIO_LED1 error "); goto err_get_gpio1; } gpio_free(gpio_led2); ret = gpio_request(gpio_led2,"GPIO_LED2"); //申请gpio_led引脚为GPIO模式 if(ret < 0){ printk("gpio_request gpio = GPIO_LED1 error "); goto err_get_gpio2; } //第三步：设置LED引脚的初始化电平 ret = gpio_direction_output(gpio_led1,0); //初始化LED１为关闭状态 if(ret < 0){ printk("gpio direction input gpio = LED１ error "); goto err_gpio_direction; } ret = gpio_direction_output(gpio_led2,0); //初始化LED２为关闭状态 if(ret < 0){ printk("gpio direction input gpio = LED2 error "); goto err_gpio_direction; } //第四步：通过杂项设备注册LED灯 ret = misc_register(&gec3399_led_misc); //注册字符设备 if(ret < 0){ printk("misc register error "); goto err_misc_register; } printk( KERN_ALERT "led dirve install succee "); return 0; err_misc_register: err_gpio_direction: gpio_free(gpio_led2); err_get_gpio2: gpio_free(gpio_led1); err_get_gpio1: return ret; } 杂项设备 static struct miscdevice gec3399_led_misc = { .minor = MISC_DYNAMIC_MINOR, .fops = &gec3399_led_fops, .name = "led_drv", }; //混杂设备结构体定义和初始化文件操作集 static struct miscdevice gec3399_led_misc = { .minor = MISC_DYNAMIC_MINOR, .fops = &gec3399_led_fops, .name = "led_drv", }; //混杂设备结构体定义和初始化控制函数 static long gec3399_led_ioctl(struct file file, unsigned int cmd, unsigned long arg) { switch(cmd) { case LED_ON: gpio_set_value(gpio_led1,1); gpio_set_value(gpio_led2,1); break; case LED_OFF: gpio_set_value(gpio_led1,0); gpio_set_value(gpio_led2,0); break; } return 0; } 完整驱动代码 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define LED_ON _IO('B',0) #define LED_OFF _IO('B',1) int gpio_led1,gpio_led2; static long gec3399_led_ioctl(struct file file, unsigned int cmd, unsigned long arg) { switch(cmd) { case LED_ON: gpio_set_value(gpio_led1,1); gpio_set_value(gpio_led2,1); break; case LED_OFF: gpio_set_value(gpio_led1,0); gpio_set_value(gpio_led2,0); break; } return 0; } static int gec3399_led_release(struct inode inode, struct file file) { gpio_set_value(gpio_led1,0); //应用程序退出时，关闭蜂鸣器 gpio_set_value(gpio_led2,0); //应用程序退出时，关闭蜂鸣器 return 0; } static const struct file_operations gec3399_led_fops = { .owner = THIS_MODULE, .unlocked_ioctl = gec3399_led_ioctl, .release = gec3399_led_release, }; //文件操作集结构体 static struct miscdevice gec3399_led_misc = { .minor = MISC_DYNAMIC_MINOR, .fops = &gec3399_led_fops, .name = "led_drv", }; //混杂设备结构体定义和初始化 static int gec3399_led_probe(struct platform_device pdev) { int ret; struct device_node led_node = pdev->dev.of_node; //enum of_gpio_flags flag; printk(KERN_ALERT"gpio-led math succee "); gpio_led1 = of_get_named_gpio(led_node,"gpio-led1", 0); //从设备树获取GPIO号 if (!gpio_is_valid(gpio_led1)) { printk("gpio-led1: %d is invalid ",gpio_led1); ret = -ENODEV; goto err_get_gpio1; } printk("gpio-led1 = %d ",gpio_led1); gpio_led2 = of_get_named_gpio(led_node,"gpio-led2", 0); //从设备树获取GPIO号 if (!gpio_is_valid(gpio_led2)) { printk("gpio-led2: %d is invalid ",gpio_led2); ret = -ENODEV; goto err_get_gpio1; } printk("gpio-led2 = %d ",gpio_led2); gpio_free(gpio_led1); ret = gpio_request(gpio_led1,"GPIO_LED1"); //申请gpio_led引脚为GPIO模式 if(ret < 0){ printk("gpio_request gpio = GPIO_LED1 error "); goto err_get_gpio1; } gpio_free(gpio_led2); ret = gpio_request(gpio_led2,"GPIO_LED2"); //申请gpio_led引脚为GPIO模式 if(ret < 0){ printk("gpio_request gpio = GPIO_LED1 error "); goto err_get_gpio2; } ret = gpio_direction_output(gpio_led1,0); //初始化LED1为关闭状态 if(ret < 0){ printk("gpio direction input gpio = ak8963c_DYDR error "); goto err_gpio_direction; } ret = gpio_direction_output(gpio_led2,0); //初始化LED2为关闭状态 if(ret < 0){ printk("gpio direction input gpio = ak8963c_DYDR error "); goto err_gpio_direction; } ret = misc_register(&gec3399_led_misc); //注册字符设备 if(ret < 0){ printk("misc register error "); goto err_misc_register; } printk( KERN_ALERT "led dirve install succee "); return 0; err_misc_register: err_gpio_direction: gpio_free(gpio_led2); err_get_gpio2: gpio_free(gpio_led1); err_get_gpio1: return ret; } static int gec3399_led_remove(struct platform_device pdev) { gpio_free(gpio_led1); gpio_free(gpio_led2); misc_deregister(&gec3399_led_misc); printk(KERN_ALERT "led dirve rmove succee "); return 0; } static const struct of_device_id of_gec_leder_match[] = { { .compatible = "gpio-led", }, //compatible 兼容属性名，需与设备树节点的属性一致 {}, }; static struct platform_driver gec3399_led_driver = { .driver = { .name ="gpio-led", .owner = THIS_MODULE, .of_match_table = of_gec_leder_match, //设备树设备匹配 }, .probe = gec3399_led_probe, //驱动探测 .remove = gec3399_led_remove, //驱动移除 }; module_platform_driver(gec3399_led_driver); //module的描述，不是必需的。#modinfo led_drv.ko MODULE_DESCRIPTION("led driver for RK3399"); MODULE_LICENSE("GPL"); //符合GPL协议 MODULE_VERSION("V1.0"); 测试代码测试代码主要实现LED的闪烁功能 #include #include #include #include #include #include #include //宏定义 #define LED_ON _IO('B',0) #define LED_OFF _IO('B',1) int main(void) { int fd_led; int ret; //第一步：打开设备节点 fd_led = open("/dev/led_drv", O_WRONLY); if(fd_led < 0) { perror("open led driver"); return -1; } while(1) { //第二步：点亮LED灯 ret = ioctl(fd_led,LED_ON); if(ret < 0) perror("write led driver "); sleep(1); //第三步：关闭LED灯 ret = ioctl(fd_led,LED_OFF); if(ret < 0 ) perror("write led driver "); sleep(1); } //第四步：关闭设备节点 close(fd_led); return 0; } Makefile文件 obj-m += led_drv.o KERNELDIR:=/file/RK3399Pro/rk3399pro_git_repo/kernel PWD:=$(shell pwd) default: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules test: aarch64-linux-gnu-gcc led_test.c -o led_test clean: rm -rf .o .order ..cmd .ko .mod.c .symvers .tmp_versions led_test 测试步骤编译源码在ubuntu中输入： make 得到驱动目标文件led_drv.ko 输入： make test 得到测试目标文件：led_test 加载驱动在开发板命令终端输入： insmod led_drv.ko 执行测试程序在开发板命令终端输入： chmod 777 led_test ./led_test 实验现象实现LED的闪烁原作者：冷静的领头狼 0
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