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ESP32-Powered Heart Rate Monitor with TFT Display and Battery Backup

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Circuit Documentation

Summary

This circuit is designed to monitor heart rate using the AD8232 Heart Rate Monitor and display the data on an ILI9341 TFT display. The circuit is controlled by an ESP32 microcontroller, which also handles user input through a push button and power control via a rocker switch. The system is powered by a 9V battery.

Component List

  1. AD8232 Heart Rate Monitor

    • Description: Monitors heart rate signals.
    • Pins: GND, 3.3v, OUTPUT, LO-, LO+, SDN, RA, LA, RL

  2. ILI9341 TFT Display

    • Description: Displays graphical data.
    • Pins: SD_CS, SD_MOSI, SD_MISO, SD_SCK, VCC, GND, CS, RESET, D/C, SD(MOSI), SCK, LED, SDO(MISO), T_CLK, T_CS, T_DIN, T_OUT, T_IRQ

  3. ESP32

    • Description: Microcontroller for processing and control.
    • Pins: EN, VP, VN, D34, D35, D32, D33, D25, D26, D27, D14, D12, D13, GND, VIN, 3V3, D15, D2, D4, RX2, TX2, D5, D18, D19, D21, RX0, TX0, D22, D23, BOOT

  4. Rocker Switch (SPST)

    • Description: Controls power to the circuit.
    • Pins: 1, 2

  5. 9V Battery

    • Description: Provides power to the circuit.
    • Pins: -, +

  6. Push Button Round

    • Description: User input for interaction.
    • Pins: leg0, leg1

Wiring Details

AD8232 Heart Rate Monitor

ILI9341 TFT Display

ESP32

Rocker Switch (SPST)

9V Battery

Push Button Round

Documented Code

ESP32 Code

#include <TFT_eSPI.h> // Include the graphics library

// Create an instance of the TFT_eSPI class
TFT_eSPI tft = TFT_eSPI(); // Call the library

// Define scale factors for amplitude and width
float scaleFactor = 0.5; // Adjust this value to change amplitude
float widthFactor = 2.0;  // Adjust this value to change width (frequency)

// Define pin for the button
const int buttonPin = 33; // Change to the pin you use for the button

void setup() {
  // Initialize serial communication:
  Serial.begin(115200); // ESP32 usually uses a higher baud rate
  pinMode(41, INPUT);   // Setup for leads off detection LO +
  pinMode(40, INPUT);   // Setup for leads off detection LO -
  pinMode(buttonPin, INPUT_PULLUP); // Set button pin as input with pull-up

  // Initialize the TFT display
  tft.init();
  tft.setRotation(1); // Set display rotation
  tft.fillScreen(TFT_BLACK); // Clear the screen with black color

  // Step 1: Display "Group Name" in the center of the screen
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(2);
  
  // Calculate position to display text in the center
  String groupName = "Group Name"; // Replace with your group name
  int textWidth = tft.textWidth(groupName);
  int textHeight = tft.fontHeight(2);
  tft.setCursor((tft.width() - textWidth) / 2, (tft.height() - textHeight) / 2);
  tft.println(groupName);

// Display names to the right of "Group Name"
String names[] = {
  "1. M.Hanif",
  "P22030123032",
  "2. Nasrul",
  "3. Izzatul",
  "4. Rafi"
};

int numberOfNames = sizeof(names) / sizeof(names[0]); // Count the number of names
int unknownX = (tft.width() - textWidth) / 2 + textWidth + 10; // 10 pixels distance from "Group Name"
int unknownY = (tft.height() - textHeight) / 10; // Same Y position as "Group Name"

for (int i = 0; i < numberOfNames; i++) {
  tft.setCursor(unknownX, unknownY + i * textHeight); // Set Y position for each line
  tft.println(names[i]);
}

  // Step 2: Display "Press button to continue" in the bottom right corner
  String promptText = "Press button to continue";
  int promptWidth = tft.textWidth(promptText);
  tft.setCursor(tft.width() - promptWidth - 10, tft.height() - textHeight - 10); // 10 pixels from the edge
  tft.println(promptText);

  // Wait until the button is pressed to continue
  while (digitalRead(buttonPin) == HIGH) {
    // Wait until the button is pressed
    delay(100);
  }

  // Display "loading..." for 3 seconds
  tft.fillScreen(TFT_BLACK); // Clear the screen
  tft.setTextColor(TFT_WHITE);
  tft.setTextSize(2);
  String loadingText = "loading...";
  int loadingTextWidth = tft.textWidth(loadingText);
  tft.setCursor((tft.width() - loadingTextWidth) / 2, (tft.height() - textHeight) / 2);
  tft.println(loadingText);
  
  delay(3000); // Delay for 3 seconds

  // Clear the screen after loading
  tft.fillScreen(TFT_BLACK);
}

void loop() {
  if ((digitalRead(41) == HIGH) || (digitalRead(40) == HIGH)) {
    Serial.println('!');
  } else {
    // Read analog value
    int analogValue = analogRead(34); // Use GPIO 34 (or other ADC pin)
    Serial.println(analogValue);

    // Draw graph
    drawGraph(analogValue);
  }
  
  // Wait a bit to prevent serial data saturation
  delay(25);
}

void drawGraph(int value) {
  static int lastX = 0; // Store last X position
  static int lastY = 0; // Store last Y position

  // Apply scale factor to analog value
  int scaledValue = value * scaleFactor; // Scale the value

  // Calculate the center of the display
  int centerY = tft.height() / 2;

  // Map the scaled value to the display height, offset by the center
  int y =