Hello all, thank you in advance for the community's help.
A classmate and I have built a SP02 sensor and connected one red LED, one IR LED and a Photo diode to the Arduino Micro.
As of right now, we are looking to get consistent data to output to the serial monitor.
We are seeing output to the monitor several seconds after turning on the device, and sometimes the output takes more than 15 seconds. Furthermore, we are getting a oxogyn concentration of a value well above 100%.
There are times when we get a HR value, and a O2 value which seem reasonable, however, this is not always the case and rather inconsistent.
Is there something wrong with the timing of the interrupts or even the frequency in which we write to the serial monitor?
The code is as follows:
#include <LiquidCrystal.h> //Including this so we can test the code as is
//We can always remove the LCD code later
#include "floatToString.h" //SEE COMMENTS BELOW
/*
* You need to include the float to string header file. I am unsure if this goes in the
* main direcotry withe the code or just the library. For completness I have incouded it on my
* computer in both locations. Please do the same untill we can test further.
*/
#include "Arduino.h" //Formally floatToString.h This changed years ago, using Arduino.h
#include <SoftwareSerial.h> //bluetooth
#include <TimerOne.h> //interrupts SEE COMMENT BELOW
//**********************************************************
//Read Below..........................................
/*
* Need a library for the above timeerOne file
* without the library, you will get an error.
* See Github at https://github.com/PaulStoffregen/TimerOne
* Download the timerOne-master.zip file and place the entire
* TimerOne-master folder in my Documents > Arduino > libraries
*/
//**********************************************************
#define analogPin A0
#define Theta 0.6
#define RxD 1 //bluetooth read
#define TxD 0 //bluetooth transmit
#define DEBUG_ENABLED //bluetooth
#define redLED 5 //High is Red led on, Low is Infrared on.
//#define iredLED 6
volatile int maxTemp,minTemp; //shared variables between interrupts and loop
volatile int lastcount,count;
int Rmax, Rmin, IRmax, IRmin;
float R, Spo2,HeartR_frq;
int Sp02_int;
int HeartRate, HeartR;
float LastHeartRate = 70; //default
int average = 140; //average is average crossing
//int average2 = 220;
int interrupts_counter =0; //count the times of interrupts
float value=0.5;
float Spo2_float;
char buffer[25];
SoftwareSerial blueToothSerial(RxD,TxD); //define bluetooth
void setup() {
pinMode(redLED, OUTPUT); //define LED
pinMode(RxD, INPUT); //bluetooth input
pinMode(TxD, OUTPUT); //bluetooth output
pinMode(analogPin, INPUT); //analog signal input
//initially switch on Red LED, after each interrupt will turn on the other
digitalWrite(redLED, HIGH);
Serial.begin(115200);
//bluetooth
setupBlueToothConnection();
//We might not need this, this might be for the LCD display. Leaving it in for now
init_interrupts();
Timer1.initialize(40000); //terrupt every 0.04 seconds
Timer1.attachInterrupt(max_min_num); //interrupt call max_min_num function
Rmax = 0;
IRmax = 0;
Rmin = 0;
IRmin = 0;
LastHeartRate = 70;
}
void loop() {
//initialize LCD
LiquidCrystal lcd(8, 9, 4, 5, 6, 7); // initialize LCD, the pins are all depends
lcd.begin(8, 2); //set up the LCD's number of columns and rows:
while(1){ //the whole while is used to avoid LCD reinitialize
digitalWrite(redLED,HIGH);
delay(2000); //let red led signal to be stable
//interrupts();
while(!((lastcount>average )&& (count<average)) ){ }
digitalWrite(redLED,HIGH);
init_interrupts();
while(!((lastcount>average )&& (count<average)) ){ }
noInterrupts(); // temporarily disabel interrupts, to be sure it will not change while we are reading
Rmax = maxTemp;
Rmin = minTemp;
delay(100);
HeartR_frq = 1/(0.04*interrupts_counter); //d is the times of ISR in 1 second,
interrupts(); //enable interrupts
HeartRate = HeartR_frq * 60;
if(HeartRate> 60 && HeartRate< 120){
HeartR = Theta*HeartRate + (1 - Theta)*LastHeartRate; //Use theta to smooth
LastHeartRate = HeartR;
}
digitalWrite(redLED, LOW);
//initialize lcd
lcd.setCursor(0,0);
lcd.print("HR:");
lcd.setCursor(5,0);
lcd.print(HeartR);
R = (Rmax - Rmin);
Spo2 = (R-180)*0.01 +97.838;
int Spo2_int = (int)Spo2; //float Spo2 to int Spo2_int
String Spo2_float = floatToString(buffer,Spo2,2);
lcd.setCursor(0,1);
lcd.print("SPO2:");
lcd.setCursor(5,1);
lcd.print(Spo2_int);
//transmit data to phone app through bluetooth
String H = String("H: ")+HeartR +String("S: ") +Spo2_float;
Serial.println(H);
delay(1000);
init_interrupts();
}
}
void setupBlueToothConnection() //initialize bluetooth
{
blueToothSerial.begin(115200); //Set BluetoothBee BaudRate to default baud rate 38400
blueToothSerial.print("\r\n+STWMOD=0\r\n"); //t the bluetooth work in slave mode
blueToothSerial.print("\r\n+STNA=HC-06\r\n"); //t the bluetooth name as "HC-05"
blueToothSerial.print("\r\n+STOAUT=1\r\n"); // Permit Paired device to connect me
blueToothSerial.print("\r\n+STAUTO=0\r\n"); // Auto-connection should be forbidden here
delay(2000); // This delay is required.
//blueToothSerial.print("\r\n+INQ=1\r\n"); //make the slave bluetooth inquirable
blueToothSerial.print("bluetooth connected!\n");
delay(2000); // This delay is required.
blueToothSerial.flush();
}
void init_interrupts()
{
maxTemp = 0;
minTemp = 1023;
count = 0;
lastcount =0;
interrupts_counter = 0;
}
void max_min_num()
{
lastcount = count;
count = analogRead(analogPin); //read signa
if(count> maxTemp){
maxTemp = count;
}
else if(count<minTemp){
minTemp = count;
}
interrupts_counter++; //interrupt counter
}
Thank you in advance for your time!