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


#define SCREEN_WIDTH 128    // OLED display width, in pixels
#define SCREEN_HEIGHT 64    // OLED display height, in pixels
#define OLED_RESET -1       // Reset pin (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3C


Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


// Base ECG waveform data points for one cycle (simulated for Lead II)
const uint8_t BASE_ECG_POINTS[] = {
    32, 34, 36, 38, 36, 34, 32,  // P Wave
    32, 32, 32,                  // Baseline
    28, 24, 48, 20, 56, 30,      // QRS Complex
    32, 32, 32,                  // Baseline
    32, 34, 36, 38, 40, 38, 36, 34, 32,  // T Wave
    32, 32, 32, 32, 32, 32, 32   // Rest of baseline
};
const int DATA_LENGTH = sizeof(BASE_ECG_POINTS) / sizeof(BASE_ECG_POINTS[0]);


int heartRate = 80;               // Initial heart rate (in bpm)
int potPin = 34;                  // Analog pin connected to potentiometer
int dataIndex = 0;


void setup() {
    Serial.begin(115200);


    // Initialize OLED display
    if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
        Serial.println(F("SSD1306 allocation failed"));
        for (;;);
    }


    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.println("ECG Signal");
    display.display();
    delay(2000);
}


void loop() {
    // Read the potentiometer and map the value to a heart rate range (60–150 bpm)
    int potValue = analogRead(potPin);
    heartRate = map(potValue, 0, 4095, 60, 150);


    // Calculate the R-R interval in milliseconds based on heart rate
    int rrInterval = 60000 / heartRate;  // ms per beat


    // Clear display before drawing the new waveform frame
    display.clearDisplay();


    // Display the heart rate on the screen
    display.setCursor(0, 0);
    display.print("Heart Rate: ");
    display.print(heartRate);
    display.println(" bpm");


    // Adjust the ECG speed based on heart rate (scroll faster at higher heart rates)
    int pointsPerBeat = map(heartRate, 60, 150, 70, 30);  // Adjust points per beat to change waveform length


    // Draw the ECG waveform across the screen width, based on heart rate
    for (int i = 0; i < SCREEN_WIDTH - 1; i++) {
        int index1 = (dataIndex + i * DATA_LENGTH / pointsPerBeat) % DATA_LENGTH;
        int index2 = (dataIndex + (i + 1) * DATA_LENGTH / pointsPerBeat) % DATA_LENGTH;


        // Calculate y-coordinates to flip the waveform vertically
        int y1 = SCREEN_HEIGHT - BASE_ECG_POINTS[index1];
        int y2 = SCREEN_HEIGHT - BASE_ECG_POINTS[index2];


        // Draw the line between two consecutive points
        display.drawLine(i, y1, i + 1, y2, SSD1306_WHITE);
    }


    display.display();


    // Increment dataIndex to shift the waveform, creating a scrolling effect
    dataIndex = (dataIndex + 1) % DATA_LENGTH;


    // Control the speed of the scrolling based on heart rate
    int delayTime = rrInterval / pointsPerBeat;  // Delay per frame to match heart rate
    delay(delayTime);
}