[设计过程分享] Max32630（四）——心率传感器

29447945 2017-9-14 10:52 楼主

现在越来越多的人们重视自己的健康，参加各类运动，强身健体，个人也喜欢跑步，但是最近好久都没跑步了。运动过程中，都需要关注的一个参数就是自己的心率，心率过高过低都不行，所以检测心率是一个很重要的参数。现在最普遍的心率传感器就是 PulseSensor 脉搏心率传感器

可以检测心率和脉搏；

原理主要就是通过光反射，转化为电压信号，单片机通过ADC采集电压，然后在通过算法得到心率和心跳；

其中算法部分代码都是现成，我们使用时只需要把ADC配置好，读取数据就可以得到需要的参数；算法部分：

void SensorTimer_handler(void)
{
float temp = 0;
unsigned int runningTotal;
ADC_GetData(&Signal); // read the Pulse Senso
temp = Signal * 1.818;
Signal = (u16)temp-1;
sampleCounter += 2; // keep track of the time in mS with this variable
Num = sampleCounter - lastBeatTime; // monitor the time since the last beat to avoid noise
ADC_StartConvert(ADC_CH_1_DIV_5, 0, 1); //restart ADC conversion
// find the peak and trough of the pulse wave
if(Signal < thresh && Num > (IBI/5)*3){ // avoid dichrotic noise by waiting 3/5 of last IBI
if (Signal < T){ // T is the trough
T = Signal; // keep track of lowest point in pulse wave
}
}
if(Signal > thresh && Signal > P){ // thresh condition helps avoid noise
P = Signal; // P is the peak
} // keep track of highest point in pulse wave
// NOW IT'S TIME TO LOOK FOR THE HEART BEAT
// signal surges up in value every time there is a pulse
if (Num > 250){ // avoid high frequency noise
if ( (Signal > thresh) && (Pulse == 0) && (Num > (IBI/5)*3) ){
Pulse = 1; // set the Pulse flag when we think there is a pulse
// HAL_GPIO_WritePin(GPIOA,GPIO_PIN_5,GPIO_PIN_SET); // turn on pin 13 LED
IBI = sampleCounter - lastBeatTime; // measure time between beats in mS
lastBeatTime = sampleCounter; // keep track of time for next pulse
if(secondBeat){ // if this is the second beat, if secondBeat == TRUE
secondBeat = 0; // clear secondBeat flag
for(int i=0; i<=9; i++){ // seed the running total to get a realisitic BPM at startup
rate[i] = IBI;
}
}
if(firstBeat){ // if it's the first time we found a beat, if firstBeat == TRUE
firstBeat = 0; // clear firstBeat flag
secondBeat = 1; // set the second beat flag
// sei(); // enable interrupts again
return; // IBI value is unreliable so discard it
}
// keep a running total of the last 10 IBI values
runningTotal = 0; // clear the runningTotal variable
for(int i=0; i<=8; i++){ // shift data in the rate array
rate[i] = rate[i+1]; // and drop the oldest IBI value
runningTotal += rate[i]; // add up the 9 oldest IBI values
}
rate[9] = IBI; // add the latest IBI to the rate array
runningTotal += rate[9]; // add the latest IBI to runningTotal
runningTotal /= 10; // average the last 10 IBI values
BPM = 60000/runningTotal; // how many beats can fit into a minute? that's BPM!
QS = 1; // set Quantified Self flag
// QS FLAG IS NOT CLEARED INSIDE THIS ISR
}
}
if (Signal < thresh && Pulse == 1){ // when the values are going down, the beat is over
// HAL_GPIO_WritePin(GPIOA,GPIO_PIN_5,GPIO_PIN_RESET); // turn off pin 13 LED
Pulse = 0; // reset the Pulse flag so we can do it again
amp = P - T; // get amplitude of the pulse wave
thresh = amp/2 + T; // set thresh at 50% of the amplitude
P = thresh; // reset these for next time
T = thresh;
}
if (Num > 2500){ // if 2.5 seconds go by without a beat
thresh = 512; // set thresh default
P = 512; // set P default
T = 512; // set T default
lastBeatTime = sampleCounter; // bring the lastBeatTime up to date
firstBeat = 1; // set these to avoid noise
secondBeat = 0; // when we get the heartbeat back
}
TMR32_ClearFlag(MXC_TMR2);
}

读值：

int BPM; // used to hold the pulse rate
u16 Signal; // holds the incoming raw data
int IBI = 600; // holds the time between beats, must be seeded!
unsigned char Pulse = 0; // true when pulse wave is high, false when it's low
unsigned char QS = 0; // becomes true when Arduoino finds a beat.
int rate[10]; // array to hold last ten IBI values
unsigned long sampleCounter = 0; // used to determine pulse timing
unsigned long lastBeatTime = 0; // used to find IBI
int P =426; // used to find peak in pulse wave, seeded
int T = 426; // used to find trough in pulse wave, seeded
int thresh = 426; // used to find instant moment of heart beat, seeded
int amp = 100; // used to hold amplitude of pulse waveform, seeded
int Num;
unsigned char firstBeat = 1; // used to seed rate array so we startup with reasonable BPM
unsigned char secondBeat = 0; // used to seed rate array so we startup with reasonable BPM
void sendDataToProcessing(char symbol, int dat )
{
putchar(symbol); // symbol prefix tells Processing what type of data is coming
printf("%d\r\n",dat); // the data to send culminating in a carriage return
}
int Sensor_Task(void)
{
static u32 PointM = 0;
uint16_t adc_val[4];
unsigned int overflow[4];
uint8_t fmtstr[40];
/* Initialize ADC */
if( ( OsDelayCCnt - PointM ) >= T_20MS)
{
PointM = OsDelayCCnt;
/* Convert channel 0 */
sendDataToProcessing('S', Signal); // send Processing the raw Pulse Sensor data
if (QS == 1)
{
User.BPM = BPM;
User.IBI = IBI;
sendDataToProcessing('B',BPM); // send heart rate with a 'B' prefix
sendDataToProcessing('Q',IBI); // send time between beats with a 'Q' prefix
QS = 0; // reset the Quantified Self flag for next time
}
/* Delay for 1/4 second before next reading */
}
}

显示：

void OLED_Task(void)
{
static u32 PointM = 0;
static u8 mState = 0;
char Data_Time[9] = "hh:mm:ss";
char Data_Data[11] = "yyyy-mm-dd";
char Data_Sensor[19] = "BMP:xxxx IBI:xxxx";
LCD_P8x16Str(36,0,"MAX32630");
// LCD_P8x16Str(0,2,"EEWORLD");
// LCD_P8x16Str(0,4,"Smart Watch");
if( ( OsDelayCCnt - PointM ) >= T_1S)
{
PointM = OsDelayCCnt;
// LCD_CLS();
sprintf(Data_Sensor,"BMP:%03d IBI:%04d",User.BPM,User.IBI);
LCD_P8x16Str(0,2,Data_Sensor);
sprintf(Data_Data,"%04d-%02d-%02d",User.RtcTime.Year + 2000,User.RtcTime.Mon,User.RtcTime.Day);
LCD_P8x16Str(0,4,Data_Data);
sprintf(Data_Time,"%02d:%02d:%02d",User.RtcTime.Hour,User.RtcTime.Min,User.RtcTime.Sec);
LCD_P8x16Str(0,6,Data_Time);
}
}