Circuit Documentation

Summary

This circuit integrates an Arduino Mega 2560 microcontroller with an AD8232 Heart Rate Monitor and an ili9341 TFT display. The purpose of the circuit is to read heart rate data from the AD8232 sensor, process it with the Arduino, and display the results on the TFT screen. The Arduino Mega 2560 also controls the display's operation, including initialization and drawing of graphical elements such as grids and text.

Component List

Arduino Mega 2560

• Description: A microcontroller board based on the ATmega2560.
• Purpose: Acts as the central processing unit for the circuit, reading sensor data, running the main program, and controlling the TFT display.

AD8232 Heart Rate Monitor

• Description: A single-lead heart rate monitor.
• Purpose: Measures electrical activity of the heart (ECG) and outputs an analog signal.

ili9341 TFT Display

• Description: A 320x240 pixel color display with SPI interface.
• Purpose: Displays the heart rate data and graphical representation of the ECG.

Wiring Details

Arduino Mega 2560

• 3V3 connected to AD8232 Heart Rate Monitor 3.3v
• 5V connected to ili9341 TFT Display VCC and LED
• GND connected to AD8232 Heart Rate Monitor GND and ili9341 TFT Display GND
• A0 connected to AD8232 Heart Rate Monitor OUTPUT
• D8 PWM connected to ili9341 TFT Display DC/RS
• D9 PWM connected to ili9341 TFT Display RESET
• D10 PWM connected to ili9341 TFT Display CS
• D11 PWM connected to ili9341 TFT Display SDI
• D12 PWM connected to ili9341 TFT Display SDO
• D13 PWM connected to ili9341 TFT Display SCK

AD8232 Heart Rate Monitor

• 3.3v connected to Arduino Mega 2560 3V3
• GND connected to Arduino Mega 2560 GND
• OUTPUT connected to Arduino Mega 2560 A0

ili9341 TFT Display

• VCC connected to Arduino Mega 2560 5V
• LED connected to Arduino Mega 2560 5V
• GND connected to Arduino Mega 2560 GND
• DC/RS connected to Arduino Mega 2560 D8 PWM
• RESET connected to Arduino Mega 2560 D9 PWM
• CS connected to Arduino Mega 2560 D10 PWM
• SDI connected to Arduino Mega 2560 D11 PWM
• SDO connected to Arduino Mega 2560 D12 PWM
• SCK connected to Arduino Mega 2560 D13 PWM

Documented Code

#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"

// Screen dimensions
#define SCREEN_WIDTH 320
#define SCREEN_HEIGHT 350

// Color definitions for the grid
#define MINOR_GRID tft.color565(100, 100, 255)
#define MAJOR_GRID tft.color565(0, 0, 255)
#define GRID_EDGE tft.color565(255, 0, 0)
#define V_CENTER tft.color565(255, 0, 0)
#define H_CENTER tft.color565(255, 0, 0)

// Pin definitions for the TFT display
#define TFT_CS         10
#define TFT_DC         8
//#define TFT_LED      5v
#define TFT_RST        9
#define TFT_MOSI       11
#define TFT_CLK        13
#define TFT_MISO       12

// Create TFT display object
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_CLK, TFT_RST, TFT_MISO);

// Variables for plotting data
int x=0;
int lastx=0;
int lasty=150;

// Variables for BPM calculation
int LastTime=0;
bool BPMTiming=false;
bool BeatComplete=false;
int BPM=0;

// Thresholds for detecting a heartbeat
#define UpperThreshold 550
#define LowerThreshold 500

// Variables for display dimensions
int lebar;
int tinggi;
int geser = 0;

void setup() {
  // Initialize the display
  tft.begin();
  tft.fillScreen(ILI9341_BLACK);
  tft.setTextSize(2);
  tft.setRotation(1); 
  drawGrid(); 
  Serial.begin(9600);
}

void loop() {
  // Update display dimensions
  lebar = tft.width(); 
  tinggi = tft.height();
  // Draw a red line at the center of the display
  tft.drawLine(0,115,lebar,115,ILI9341_RED);
  
  // Clear the display and redraw the grid when reaching the end
  if(x > lebar)  {
    tft.fillRect(0,80,320,75,ILI9341_BLACK);
    x=0;
    lastx=x;
    drawGrid();
  }

  // Read ECG data from the heart rate monitor
  int dataecg = analogRead(A0);
  
  // Plot the ECG data on the display
  int y = 150 - ( dataecg / 10 );
  tft.drawLine(lastx,lasty,x,y,ILI9341_WHITE);
  lasty = y;
  lastx = x;

  // BPM calculation logic
  if( dataecg > UpperThreshold ) {
    if(BeatComplete) {
      BPM=millis()-LastTime;
      BPM=int(60/(float(BPM)/1000));
      BPMTiming=false;
      BeatComplete=false;
    }
    if(BPMTiming==false) {
      LastTime=millis();
      BPMTiming=true;
    }
  }
  if((dataecg < LowerThreshold)&(BPMTiming))
    BeatComplete=true;
  
  // Display BPM on the screen
  tft.setCursor(5, 10);
  tft.setTextColor(ILI9341_YELLOW,ILI9341_BLACK);  
  tft.print("BPM: ");  
  tft.print(BPM);  
  tft.print("   ");  
  
  // Increment the x position for the next data point
  x = x + 3;
}

// Function to draw the grid on the display
void drawGrid() {
  // Draw minor grid lines
  for (int v = 5; v < SCREEN_WIDTH; v += 10) {
    tft.drawFastVLine(v, 0, SCREEN_HEIGHT, MINOR_GRID);
  }
  for (int h = 5; h < SCREEN_HEIGHT; h += 10) {
    tft.drawFastHLine(0, h, SCREEN_HEIGHT, MINOR_GRID);
  }

  // Draw major grid lines
  for (int v = 10; v < SCREEN_WIDTH; v += 10) {
    tft.drawFastVLine(v, 0, SCREEN_HEIGHT, MAJOR_GRID);
  }
  for (int h = 10; h < SCREEN_HEIGHT; h += 10) {
    tft.drawFastHLine(0, h, SCREEN_HEIGHT, MAJOR_GRID);
  }

  // Draw edge lines
  tft.drawFastVLine(0, 0, SCREEN_HEIGHT - 1, GRID_EDGE);
  tft.drawFastVLine(SCREEN_WIDTH - 1, 0, SCREEN_HEIGHT - 1, GRID_EDGE);
  tft.drawFastHLine(0, 0, SCREEN_WIDTH - 1, GRID_EDGE);
  tft.drawFastHLine(0, SCREEN_HEIGHT - 1, SCREEN_HEIGHT - 1, GRID_EDGE);

  // Draw center lines
  tft.drawFastVLine(SCREEN_WIDTH / 2, 0, SCREEN_HEIGHT, V_CENTER);
}

This code is designed to run on the Arduino Mega 2560 and interfaces with the ili9341 TFT display to graphically represent ECG data from the AD8232 Heart Rate Monitor. It includes functions for initializing the display, drawing a grid for the ECG data, and plotting the data points as they are read from the sensor. The code also calculates and displays the beats per minute (BPM) based on the ECG signal.