STM32 MCU uses ADC function to drive finger heartbeat detection module

One 、 Module introduction

A treasure or a lot , Twoorthree yuan each , Here's the picture .

The module adopts ultra bright infrared LED And phototransistor to detect the pulse of the finger , Place your finger between the transmitter and receiver , Blood pressure changes with the pulse , The light received by the receiving end will change accordingly , Therefore, it can be used to detect heartbeat .

Two 、STM32MX Cube To configure

use STM32F103C8T6 Minimum system board ,STM32MX Cube Configure the system and automatically generate code .

stay ADC1 in , We choose IN1 passageway , namely PA1 Pin , Other configurations are shown in the figure , Basically, the default configuration , There is no need to choose . When all configuration is complete , Generate engineering code , This article will not introduce in detail .

3、 ... and 、 Main code

ADC The initialization code for is in MX_ADC1_Init() in , Generated main Function will automatically call ：

MX_ADC1_Init();

It's going on AD On conversion , You need to call HAL_ADC_Start(&hadc1) The function starts to convert , We don't use interrupts , adopt while (HAL_ADC_PollForConversion(&hadc1,10) != HAL_OK) To wait for the conversion to complete , And then through HAL_ADC_GetValue(&hadc1) Function to obtain AD value ,HAL_ADC_Stop(&hadc1) Function ends the conversion . Each of the above processes 10ms Do it once , Sampling frequency 100Hz.

	HAL_ADC_Start(&hadc1);
	while (HAL_ADC_PollForConversion(&hadc1,10) != HAL_OK)// Wait for the conversion to complete 
	{
    
	}
	HeartBeat_RawData = HAL_ADC_GetValue(&hadc1);//RAW_DATA_LENGTH Is the number of data saved 
	HAL_ADC_Stop(&hadc1);
	printf("%d\n", HeartBeat_RawData);

In the above code printf Function to print data to serial port . see , You need to write your own code , Not many lines .

Four 、 Running effect

The above figure is through the serial port drawing software VOFA+ The original drawing AD The graph of values , It can be seen that the data is messy , The green line in the figure below is the effect after simple filtering ：

5、 ... and 、 summary

1. Actual test findings , This module has a great impact on the environment , Day 、 night , turn on the light 、 Turning off the lights will have a great impact on the data , And data often drift ;
2. Just read the data , Simple filtering , From the time domain diagram , I can't find any rules ;
3. If it's just for learning ADC Use , You can use this module to practice , These data can also be used to learn the filtering algorithm 、 Fourier transform, etc , But I want to use it to detect the heartbeat more accurately , I still don't recommend .