STM32F4 ADC多通道中断逻辑错误排查求助

问题描述 #

使用STM32F4的ADC中断功能，PA0、PA1作为模拟输入，PC0、PC1接外部LED。预期PA0输入高电平时PC0点亮，PA1输入高电平时PC1点亮，但实际PA0加3.3V时两个LED都亮，PA1触发无反应，硬件无问题，代码存在两处逻辑错误。

错误定位与修正 #

错误1：ADC中断标志位未清除 #

中断函数中仅判断了EOC（转换完成）标志位，但未清除该标志，导致中断不断触发，adc_index快速循环切换，两个LED的控制逻辑被连续执行，最终出现双灯同时点亮的情况。

修正方法：在中断处理完成后清除EOC标志位：

ADC1->SR &= ~(0x1 << 1);

错误2：ADC通道1采样时间未配置 #

代码中仅配置了ADC通道0（PA0）的采样时间，通道1（PA1）的采样时间未设置，默认采样时间过短，导致PA1的ADC转换数据不准确，无法触发LED控制逻辑。

修正方法：添加通道1的采样时间配置：

// 通道1采样时间84周期
ADC1->SMPR2 &= ~(0x7 << 3);
ADC1->SMPR2 |= (0x4 << 3);

修正后的完整代码 #

#include "main.h"
volatile uint8_t adc_index = 0;
void SystemClock_Config(void);

void ADC_IRQHandler(void)
{
    if(ADC1->SR & (0x1 << 1))
    {
        uint8_t val = (uint8_t)ADC1->DR;
        if(adc_index == 0)
        {
            if(val > 127)
                GPIOC->BSRR = (1 << 0);
            else
                GPIOC->BSRR = (1 << 16);
        }
        else
        {
            if(val > 127)
                GPIOC->BSRR = (1 << 1);
            else
                GPIOC->BSRR = (1 << 17);
        }
        adc_index++;
        if(adc_index >= 2) adc_index=0;
        
        // 清除EOC中断标志位
        ADC1->SR &= ~(0x1 << 1);
    }
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();

  RCC->AHB1ENR |= (0x5 << 0);
  RCC->APB2ENR |= (0x1 << 8);

  // PA0 as Analog Input for ADC
  GPIOA->MODER |= (0x3 << 0);
  // PA1 as Analog Input for ADC
  GPIOA->MODER |= (0x3 << 2);
  // PC1 as General output for external Led
  GPIOC->MODER &= ~(0x3 << 2);
  GPIOC->MODER |= (0x1 << 2);
  // PC0 as General output for external Led
  GPIOC->MODER &= ~(0x3 << 0);
  GPIOC->MODER |= (0x1 << 0);

  // ADC Cont mode on
  ADC1->CR2 |= (0x1 << 1);
  // Interrupt enable for ADC
  ADC1->CR1 |= (0x1 << 5);

  // 8 bit Resolution
  ADC1->CR1 &= ~(0x3 << 24);
  ADC1->CR1 |= (0x2 << 24);

  // 2 Channel conversion
  ADC1->SQR3 |= (0x0 << 0);
  ADC1->SQR3 |= (0x1 << 5);

  // 2 CONVERSION Selected
  ADC1->SQR1 |= (0x1 << 20);

  // Sample Rate 84 CYCLES for Channel 0
  ADC1->SMPR2 &= ~(0x7 << 0);
  ADC1->SMPR2 |= (0x4 << 0);
  // Sample Rate 84 CYCLES for Channel 1
  ADC1->SMPR2 &= ~(0x7 << 3);
  ADC1->SMPR2 |= (0x4 << 3);

  // ADC_IRQHandler unmasked
  NVIC->ISER[0] = (0x1 << 18);

  // ADC On
  ADC1->CR2 |= (0x1 << 0);

  // Software Start
  ADC1->CR2 |= (0x1 << 30);

  while (1)
  {

  }
}

验证说明 #

修正后，PA0输入3.3V时，ADC转换值大于127，PC0点亮；PA1输入3.3V时，PC1点亮，符合预期功能。

内容的提问来源于stack exchange，提问作者Umutcan Akyol