使用GD32F303标准库编写一个定时器7捕获PWM，并更新定时器0的PWM占空比

本题需要使用定时器7的输入捕获功能，获取PWM信号的占空比，然后根据占空比更新定时器0的PWM占空比。

首先，需要初始化定时器7和定时器0。定时器7需要配置为输入捕获模式，定时器0需要配置为PWM输出模式。

// 初始化定时器7
timer_input_capture_parameter_struct timer_icinitpara;
timer_icinitpara.icpolarity = TIMER_IC_POLARITY_FALLING;
timer_icinitpara.icselection = TIMER_IC_SELECTION_DIRECTTI;
timer_icinitpara.icprescaler = TIMER_IC_PSC_DIV1;
timer_icinitpara.icfilter = 0x00;
timer_icinitpara.capturealignment = TIMER_IC_EDGE;
timer_icinit(TIMER7, TIMER_CH_1, &timer_icinitpara);

// 初始化定时器0
timer_parameter_struct timer_initpara;
timer_initpara.prescaler = 107;  // 时钟预分频值
timer_initpara.alignedmode = TIMER_COUNTER_EDGE;
timer_initpara.counterdirection = TIMER_COUNTER_UP;
timer_initpara.period = 999;  // PWM周期
timer_initpara.clockdivision = TIMER_CKD_DIV1;
timer_init(TIMER0, &timer_initpara);

timer_oc_parameter_struct timer_ocinitpara;
timer_ocinitpara.ocpolarity = TIMER_OC_POLARITY_HIGH;
timer_ocinitpara.ocnpolarity = TIMER_OCN_POLARITY_HIGH;
timer_ocinitpara.ocidlestate = TIMER_OC_IDLE_STATE_LOW;
timer_ocinitpara.ocnidlestate = TIMER_OCN_IDLE_STATE_LOW;
timer_ocinitpara.compare = 0;  // 初始占空比为0
timer_ocinitpara.ochyperpolarity = TIMER_OC_HYPERPOLARITY_ENABLE;
timer_ocinitpara.ocmode = TIMER_OC_MODE_PWM1;
timer_channel_output_config(TIMER0, TIMER_CH_0, &timer_ocinitpara);

然后，需要编写定时器7的输入捕获中断处理函数，获取PWM信号的占空比。在中断处理函数中，需要获取当前定时器7的计数值和上一次捕获到的计数值，计算出PWM的周期和占空比，并将占空比存储到一个全局变量中。

// 全局变量，保存PWM占空比
volatile uint16_t pwm_duty_cycle = 0;

void TIMER7_IRQHandler(void)
{
    if (timer_flag_get(TIMER7, TIMER_FLAG_CH1)) {
        // 清除捕获中断标志
        timer_flag_clear(TIMER7, TIMER_FLAG_CH1);

        static uint32_t last_count = 0;
        static uint32_t current_count = 0;

        // 获取当前计数值
        current_count = timer_channel_capture_value_register(TIMER7, TIMER_CH_1);
        // 计算PWM周期和占空比
        uint32_t period = current_count - last_count;
        last_count = current_count;
        pwm_duty_cycle = (uint16_t)(timer_channel_capture_value_register(TIMER7, TIMER_CH_1) * 1000 / period);
    }
}

最后，在主函数中循环更新定时器0的占空比。由于定时器0的PWM周期是固定的，所以只需要根据占空比计算对应的计数值，然后调用函数更新定时器0的占空比即可。

while (1) {
    // 根据占空比计算对应的计数值
    uint16_t compare = pwm_duty_cycle * 1000 / 100;
    timer_channel_output_pulse_value_config(TIMER0, TIMER_CH_0, compare);
}

完整代码如下：