中心对齐PWM波形，并未中心对齐

发布于 2022-06-19 12:29:06 浏览：750 订阅该版

芯片：STM32F411CEU6
rt-thread: 4.1.0
rt-thread studio: 2.2.3 构建ID: 202204221442

**问题：**
在CubeMx中配置TM1_CH1，TIM1_CH4输出两路PWM，Counter Mode设置为Center Aligned mode1，期望输出两路中心对齐的PWM波形。但是在rt_thread代码中实际输出并非中心对齐，而是UP对齐模式波形。

**1、两路PWM，中心输出配置：**
![camode.png](https://oss-club.rt-thread.org/uploads/20220619/8b9c13db4c4a5bae90077788dbb12e53.png "camode.png")

**2、输出两路PWM波形代码：**
```c
/* 使用PWM设备 */
struct rt_device_pwm *hv_pwm_device = RT_NULL; //定义PWM设备指针
rt_uint32_t period, pulse;

#define HV_PWM_DEVICE "pwm1"
#define HV_PWM_CHA  1
#define HV_PWM_CHB  4

int main(void)
{
    int count = 1;

period = 50000;    /* 单位为纳秒ns , 周期为0.5ms，即为2KHz*/
    pulse = 20000;

/* 插找PWM设备 */
    hv_pwm_device = (struct rt_device_pwm *)rt_device_find(HV_PWM_DEVICE);
    if(hv_pwm_device == RT_NULL)
    {
        LOG_E("HV PWM Device %s not found!", HV_PWM_DEVICE);
        return -RT_ERROR;
    }

//设置PWM参数
    rt_pwm_set(hv_pwm_device, HV_PWM_CHA, period, pulse);
    rt_pwm_set(hv_pwm_device, HV_PWM_CHB, period, period - pulse);

//使能PWM输出
    rt_pwm_enable(hv_pwm_device, HV_PWM_CHA);
    rt_pwm_enable(hv_pwm_device, HV_PWM_CHB);

while (count++)
    {
        //LOG_D("Hello RT-Thread!");
        rt_thread_mdelay(1000);
    }

return RT_EOK;
}
```
**3、实际输出波形**
如下图，实际输出的波形，并非中心对齐的。而是与Counter Mode = UP 的波形一致。
![came.png](https://oss-club.rt-thread.org/uploads/20220619/481a576fbb88e32adc18bcf083fd3fb7.png.webp "came.png")