Pulsesensor在stm32f4的程序

下面是一个基于STM32F4的程序，使用PulseSensor传感器来测量心率：

#include "stm32f4xx.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_tim.h"
#include "misc.h"

#define PULSESENSOR_PIN GPIO_Pin_0
#define PULSESENSOR_GPIO_PORT GPIOA
#define PULSESENSOR_GPIO_CLK RCC_AHB1Periph_GPIOA

#define TIMER_PERIOD 5000 // 5ms

volatile uint16_t pulse_count = 0;
volatile uint16_t last_pulse_count = 0;
volatile uint16_t bpm = 0;

void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_AHB1PeriphClockCmd(PULSESENSOR_GPIO_CLK, ENABLE);

  GPIO_InitStructure.GPIO_Pin = PULSESENSOR_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_Init(PULSESENSOR_GPIO_PORT, &GPIO_InitStructure);
}

void TIM_Configuration(void)
{
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  TIM_TimeBaseStructure.TIM_Period = TIMER_PERIOD - 1;
  TIM_TimeBaseStructure.TIM_Prescaler = SystemCoreClock / TIMER_PERIOD - 1;
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

  TIM_Cmd(TIM2, ENABLE);
}

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

  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

  NVIC_InitTypeDef NVIC_InitStructure;
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  while (1)
  {
    if (pulse_count != last_pulse_count)
    {
      bpm = (float)pulse_count / TIMER_PERIOD * 60000;
      last_pulse_count = pulse_count;
    }
  }
}

void TIM2_IRQHandler(void)
{
  if (GPIO_ReadInputDataBit(PULSESENSOR_GPIO_PORT, PULSESENSOR_PIN))
  {
    pulse_count++;
  }

  TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
}

此程序使用STM32F4的TIM2定时器来测量脉冲数量，并计算心率。在程序中，我们使用了GPIOA的0号引脚来接收PulseSensor传感器的脉冲信号。在`GPIO_Configuration()`函数中，我们将该引脚配置为输入模式，上拉电阻使其默认为高电平。在`TIM_Configuration()`函数中，我们配置了TIM2定时器，使其每5ms触发一次中断，我们在中断中检测引脚状态，如果为高电平，则计数器加1。在`main()`函数中，我们通过轮询的方式计算心率。