RT-Thread pwm输入捕获程序

下面是一个基于RT-Thread的PWM输入捕获程序示例：

#include <rtthread.h>
#include <rtdevice.h>

#define PWM_PIN         0       // PWM输入引脚
#define CAPTURE_TICKS   2       // 捕获计数器溢出值
#define CAPTURE_MAX     0xFFFF  // 捕获计数器最大值

static rt_base_t capture_value = 0;

static void capture_isr(rt_device_t dev, rt_size_t size)
{
    rt_uint32_t isr;
    rt_uint32_t ccr;
    rt_uint32_t cnt;

    isr = rt_device_read(dev, 0, &isr, 4);
    if ((isr & (1 << 1)) == 0)
        return;

    ccr = rt_device_read(dev, 4, &ccr, 4);
    cnt = rt_device_read(dev, 8, &cnt, 4);

    if (ccr == 1)
        capture_value = cnt;
    else if (ccr == 2)
        capture_value = CAPTURE_MAX - cnt;

    rt_device_write(dev, 0, &isr, 4);
}

static void capture_thread_entry(void *parameter)
{
    rt_device_t pwm_dev;
    rt_device_t capture_dev;

    rt_uint32_t pwm_cfg[3] = {PWM_PIN, 500000, 50};
    rt_uint32_t capture_cfg[2] = {CAPTURE_TICKS, RT_DEVICE_FLAG_INT_RX};

    pwm_dev = rt_device_find("pwm");
    if (pwm_dev == RT_NULL)
    {
        rt_kprintf("PWM device not found\n");
        return;
    }

    capture_dev = rt_device_find("capture");
    if (capture_dev == RT_NULL)
    {
        rt_kprintf("Capture device not found\n");
        return;
    }

    rt_device_control(pwm_dev, PWM_CMD_ENABLE, RT_NULL);
    rt_device_control(capture_dev, RT_DEVICE_CTRL_SET_INT_MODE, &capture_cfg[1]);
    rt_device_open(capture_dev, RT_DEVICE_FLAG_INT_RX);

    while (1)
    {
        rt_device_read(capture_dev, 0, RT_NULL, 0);
        rt_kprintf("Capture value: %d\n", capture_value);
    }
}

int pwm_capture_init(void)
{
    rt_thread_t tid;

    tid = rt_thread_create("capture", capture_thread_entry, RT_NULL, 1024, 25, 10);
    if (tid == RT_NULL)
    {
        return -1;
    }
    rt_thread_startup(tid);

    return 0;
}

这个程序包括一个线程和一个中断服务程序，线程用于读取捕获值并输出到控制台。中断服务程序捕获PWM输入引脚的上升沿和下降沿，并根据捕获值计算PWM周期和占空比。在这个示例中，我们只是简单地输出捕获值，您可以根据自己需要进行修改。

要使用这个程序，您需要将PWM输入引脚连接到捕获引脚，并在RT-Thread中启用PWM和捕获设备。然后调用`pwm_capture_init`函数启动线程。