RT-thread 设备驱动组件之PIN设备

      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。本文主要涉及的pin设备文件有：驱动框架文件（pin.c，pin.h），底层硬件驱动文件（gpio.c，gpio.h）。在应用用PIN设备时，需要在rtconfig.h中宏定义#define RT_USING_PIN。

一、PIN设备驱动框架

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，在pin.c文件中将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、底层硬件驱动

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 _hw_pin设备，其设备名称为“pin”，PIN设备硬件初始化：

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、PIN设备初始化

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);