#include <Wire.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const int ecgPin = 4;  // GPIO4 where the ECG signal is input

void setup() {
  Serial.begin(115200);
  pinMode(ecgPin, INPUT);

  // Initialize the OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
}

void loop() {
  // Array to hold ECG samples for displaying
  int ecgValues[SCREEN_WIDTH];

  // Read ECG signal from custom chip and store values
  for (int i = 0; i < SCREEN_WIDTH; i++) {
    int ecgSignal = analogRead(ecgPin);  // Capture ECG signal from GPIO4
    ecgValues[i] = map(ecgSignal, 0, 4095, 0, SCREEN_HEIGHT);  // Scale to screen height
    delay(10);  // Small delay for smoother waveform (tune this based on your signal speed)
  }

  // Clear the display
  display.clearDisplay();

  // Draw ECG waveform
  for (int i = 1; i < SCREEN_WIDTH; i++) {
    display.drawLine(i - 1, ecgValues[i - 1], i, ecgValues[i], SSD1306_WHITE);
  }

  // Display BPM (Optional)
  display.setCursor(0, 0);
  display.print("ECG Signal");

  // Update the display with new data
  display.display();

  delay(10);  // Small delay before next loop
}