写一个stm32f103c8t6驱动mq-3的代码

很高兴为您服务！以下是基于STM32F103C8T6驱动MQ-3的代码：

#include "stm32f10x.h"

#define MQ3_PIN_ANALOG_IN   GPIO_Pin_0
#define MQ3_ADC_PORT        GPIOA
#define MQ3_ADC_CHANNEL     ADC_Channel_0
#define ADC1_DR_Address     ((uint32_t)0x4001244C)

ADC_InitTypeDef ADC_InitStructure;

volatile uint32_t adc_raw_val = 0;

void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

  GPIO_InitStructure.GPIO_Pin = MQ3_PIN_ANALOG_IN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(MQ3_ADC_PORT, &GPIO_InitStructure);
}

void ADC_Configuration(void)
{
  DMA_InitTypeDef DMA_InitStructure;

  RCC_ADCCLKConfig(RCC_PCLK2_Div6);
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

  ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfChannel = 1;
  ADC_Init(ADC1, &ADC_InitStructure);

  //配置PA0通道的DMA
  DMA_DeInit(DMA1_Channel1);
  DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) &adc_raw_val;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  DMA_InitStructure.DMA_BufferSize = 1;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);

  //ADC配置，开启温度传感器和采样速率
  ADC_RegularChannelConfig(ADC1, MQ3_ADC_CHANNEL, 1, ADC_SampleTime_55Cycles5);
  ADC_DMACmd(ADC1, ENABLE);
  ADC_Cmd(ADC1, ENABLE);

  //开启DMA，开始读取AD值
  DMA_Cmd(DMA1_Channel1, ENABLE);
}

int main(void)
{
  GPIO_Configuration();
  ADC_Configuration();

  //循环读取MQ-3传感器
  while(1) {
    int adc_val_mv = (int)(adc_raw_val * (3300.0/4096.0));
    int ppm = (adc_val_mv/2.0) + 100; //计算出ppm值
    //传输至上位机等操作
  }

  return 0;
}

请注意，以上代码仅为参考示例，请根据具体硬件环境进行修改。