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在RT-thread 2.0.0正式版中引入了pin设备作为杂类设备，其设备驱动文件pin.c在rt-thread-2.0.1\components\drivers\misc中，主要用于操作芯片GPIO， 如点亮led，按键等。同时对于相应的芯片平台，需要自行编写底层gpio驱动，如gpio.c。
一、在pin.c中定义了一个静态的pin设备对象static struct rt_device_pin _hw_pin，其中结构体类型struct rt_device_pin在pin.h中定义为：
/* pin device and operations for RT-Thread */ struct rt_device_pin { struct rt_device parent; const struct rt_pin_ops *ops; };
struct rt_device_pin_mode { rt_uint16_t pin; //pin index in pins[] of gpio.c rt_uint16_t mode; }; struct rt_device_pin_status { rt_uint16_t pin; //pin index in pins[] of gpio.c rt_uint16_t status; }; struct rt_pin_ops { void (*pin_mode)(struct rt_device *device, rt_base_t pin, rt_base_t mode); void (*pin_write)(struct rt_device *device, rt_base_t pin, rt_base_t value); int (*pin_read)(struct rt_device *device, rt_base_t pin); /* TODO: add GPIO interrupt */ };
在pin.c中主要实现了_pin_read，_pin_write，_pin_control三个函数，同时将这三个函数注册为_hw_pin设备的统一接口函数：
int rt_device_pin_register(const char *name, const struct rt_pin_ops *ops, void *user_data) { _hw_pin.parent.type = RT_Device_Class_Miscellaneous; _hw_pin.parent.rx_indicate = RT_NULL; _hw_pin.parent.tx_complete = RT_NULL; _hw_pin.parent.init = RT_NULL; _hw_pin.parent.open = RT_NULL; _hw_pin.parent.close = RT_NULL; _hw_pin.parent.read = _pin_read; _hw_pin.parent.write = _pin_write; _hw_pin.parent.control = _pin_control; _hw_pin.ops = ops; _hw_pin.parent.user_data = user_data; /* register a character device */ rt_device_register(&_hw_pin.parent, name, RT_DEVICE_FLAG_RDWR); return 0; }
最后，将rt_pin_mode，rt_pin_write，rt_pin_read三个函数加入到finsh的函数列表中，用于调试。
二、在gpio.c中主要实现struct rt_pin_ops中的三个接口函数：stm32_pin_mode，stm32_pin_write，stm32_pin_read：
const static struct rt_pin_ops _stm32_pin_ops = { stm32_pin_mode, stm32_pin_write, stm32_pin_read, };
同时注册pin设备，其设备名称为“pin”：
int stm32_hw_pin_init(void) { rt_device_pin_register("pin", &_stm32_pin_ops, RT_NULL); return 0; } INIT_BOARD_EXPORT(stm32_hw_pin_init);//stm32_hw_pin_init will be called in rt_components_board_init()
三、在使用pin设备时，需要在rtconfig.h中宏定义RT_USING_PIN。同时在gpio.c中修改使用的IO口数组：
/* STM32 GPIO driver */ struct pin_index { int index; uint32_t rcc; GPIO_TypeDef *gpio; uint32_t pin; }; /* LED ->PD12,PD13,PD14,PD15; USER Button->PA0 */ static const struct pin_index pins[] = { { 0, RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_12}, //green { 1, RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_13}, //orange { 2, RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_14}, //red { 3, RCC_AHB1Periph_GPIOD, GPIOD, GPIO_Pin_15}, //blue { 4, RCC_AHB1Periph_GPIOA, GPIOA, GPIO_Pin_0}, //user button };
此外在gpio_pin.c的外设初始化函数中，需要先调用rt_device_open函数（尽管该函数没有在底层实现），保证pin设备对象类的设备引用计数值ref_count不为0，这样才可正常使用rt_device_control，rt_device_write，rt_device_read函数操作GPIO口：
static struct rt_device_pin_mode led_mode[]= { {0,PIN_MODE_OUTPUT}, {1,PIN_MODE_OUTPUT}, {2,PIN_MODE_OUTPUT}, {3,PIN_MODE_OUTPUT}, }; static struct rt_device_pin_status led_status[]= { {0,PIN_HIGH}, /* 0:green on */ {1,PIN_HIGH}, /* 1:orange on */ {2,PIN_HIGH}, /* 2:red on */ {3,PIN_HIGH}, /* 3:blue on */ {0,PIN_LOW}, /* 4:green off */ {1,PIN_LOW}, /* 5:orange off */ {2,PIN_LOW}, /* 6:red off */ {3,PIN_LOW}, /* 7:blue off */ }; /* it can‘t be PIN_MODE_INPUT_PULLUP, or the key always will keep PIN_HIGH status */ static struct rt_device_pin_mode key_mode = {4,PIN_MODE_INPUT}; static struct rt_device_pin_status key_status = {4,PIN_LOW}; static struct rt_device_pin * pin_device;
static rt_err_t gpio_pin_init(const char * pin_device_name) { pin_device = (struct rt_device_pin *)rt_device_find(pin_device_name); if(pin_device == RT_NULL) { rt_kprintf("pin device for gpio %s not found!\r\n", pin_device_name); return -RT_ENOSYS; } /* oflag has no meaning for pin device , so set to RT_NULL */ if(rt_device_open(&pin_device->parent, RT_NULL) == RT_EOK) { /* init led */ for(int i=0; i<(sizeof(led_mode)/sizeof(led_mode[0])); i++) { rt_device_control(&pin_device->parent, RT_NULL, &led_mode[i]); rt_device_write(&pin_device->parent, RT_NULL, &led_status[i], sizeof(led_status[i]));//init all led PIN_HIGH } /* init key */ rt_device_control(&pin_device->parent, RT_NULL, &key_mode); } return 0; } int rt_gpio_pin_init(void) { gpio_pin_init("pin"); return 0; } INIT_APP_EXPORT(rt_gpio_pin_init);
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原文地址：http://www.cnblogs.com/King-Gentleman/p/4649713.html
