【内核学习营】+王秀峰+pwm_breathe

发布于 2018-09-12 00:30:41 浏览：1526 订阅该版

[tocm]

## 实验要求：

## 准备工作

### 硬件准备：
正点原子Explore开发板，一颗三色LED，使用串口2

### 软件准备
stm32f4xx-HAL BSP，env0.7.1、rtt3.1.0、scons

**示例代码**
```c
#include <rtthread.h> 
#include <rtdevice.h> 
#include "board.h"

#define     PERIOD    512 
#define     CH_R    1
#define     CH_G    2
#define     CH_B    3
extern rt_err_t rt_pwm_enable(int channel);
extern rt_err_t rt_pwm_set(int channel, rt_uint32_t period, rt_uint32_t pulse);
uint16_t indexWave[] = {
1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 7, 7, 8, 8, 9, 9, 10, 11, 12,
12, 13, 14, 15, 17, 18, 19, 20, 22,
23, 25, 27, 29, 31, 33, 36, 38, 41,
44, 47, 51, 54, 58, 63, 67, 72, 77,
83, 89, 95, 102, 110, 117, 126, 135,
145, 156, 167, 179, 192, 206, 221, 237,
254, 272, 292, 313, 336, 361, 387, 415,
445, 477, 512, 512, 477, 445, 415, 387,
361, 336, 313, 292, 272, 254, 237, 221,
206, 192, 179, 167, 156, 145, 135, 126,
117, 110, 102, 95, 89, 83, 77, 72, 67, 63,
58, 54, 51, 47, 44, 41, 38, 36, 33, 31, 29,
27, 25, 23, 22, 20, 19, 18, 17, 15, 14, 13,
12, 12, 11, 10, 9, 9, 8, 8, 7, 7, 6, 6, 5, 5,
5, 4, 4, 4, 4, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2,
2, 2, 1, 1, 1, 1, 1, 1
};
/*计算PWM表有多少个元素*/
rt_uint16_t POINT_NUM = sizeof(indexWave)/sizeof(indexWave[0]); 
void rt_pwm_breathe_entry(void *parameter)
{
        rt_uint16_t i = 0;
    
    /*使能各通道*/
        rt_pwm_enable(CH_R);
        rt_pwm_enable(CH_G);
        rt_pwm_enable(CH_B);
        while(1)
        {
                rt_pwm_set(CH_R, PERIOD, indexWave*);
                rt_pwm_set(CH_G, PERIOD, indexWave*);
                rt_pwm_set(CH_B, PERIOD, indexWave*);
                if(i >= POINT_NUM-1) i = 0;
                else i++;
                /* 设置整个呼吸过程为3秒左右即可达到很好的效果 */
                rt_thread_delay(300/POINT_NUM);
        }
}
int rt_breathe_init()
{
        rt_device_t pwm_dev;
        rt_thread_t tid;
        pwm_dev = rt_device_find("pwm1");
        if(NULL != pwm_dev)
        {
                tid = rt_thread_create("pwm_led",
                                                        rt_pwm_breathe_entry, 
                                                        RT_NULL,
                                                        512, 
                                                        RT_THREAD_PRIORITY_MAX/3, 
                                                        20);
                if (tid != RT_NULL)
                rt_thread_startup(tid);
        } 
        return 0;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(rt_breathe_init, rgb breathe by pwm.);
```

实验步骤
在env中打开PWM1，打开rtconfig.h文件添加宏

```c
#define BSP_USING_PWM1_CH1
#define BSP_USING_PWM1_CH2
#define BSP_USING_PWM1_CH3
#define BSP_USING_PWM1_CH4
```

查找drv_pwm文件，确定通道对应的引脚
![1.png](/uploads/201809/12/002206ovocsd36qck3gxhi.png)

## 结果
编译运行，在`msh shell` 终端中输入`rt_breathe_init`，实际上三颗灯是全亮的，拍摄效果不太好。

![2.gif](/uploads/201809/12/002216hn9nl99sdx2v1p1o.gif)

### 遇到的问题及解决方法
在第一次尝试的时候打开了PWM1，PWM2，PWM3，结果运行的的时候串口无法输入，检查发现使用的串口2和PWM2通道3冲突，关闭PWM2、3后第二次尝试还是没有结果，
查看程序打开PWM设备失败，因为PWM1注册的时候使用的是"pwm1"，修改之后依旧不行，手动添加宏之后达到实验效果。

```c
#define BSP_USING_PWM1_CH1
#define BSP_USING_PWM1_CH2
#define BSP_USING_PWM1_CH3
#define BSP_USING_PWM1_CH4
```