#include <Wire.h>
#include <Arduino.h>
#include <Adafruit_GFX.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);

// Pin Mapping
#define SIGNAL_PIN 0   // ADC input (GPIO0 → your oscilloscope input)
#define SDA_PIN    3   // I2C SDA
#define SCL_PIN    4   // I2C SCL
#define PWM_PIN    5   // PWM output (GPIO3)


// ADC Parameters
#define NUM_SAMPLES 128
int samples[NUM_SAMPLES];

void setup() {
  pinMode(PWM_PIN, OUTPUT);

  // Initialize I2C for OLED
  Wire.begin(SDA_PIN, SCL_PIN);

  // Initialize OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    for (;;); // Halt if OLED not found
  }
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0,0);
  display.println("ESP32-C3 Oscilloscope");
  display.display();
  delay(1000);

  // Setup ADC
  analogReadResolution(10);   // 10-bit ADC (0–1023)
}

void loop() {

   // Generate a PWM wave by varying duty cycle
  for (int duty = 0; duty <= 255; duty++) {
    analogWrite(PWM_PIN, duty);  // duty cycle: 0-255
    delay(10);
  }

  for (int duty = 255; duty >= 0; duty--) {
    analogWrite(PWM_PIN, duty);
    delay(10);
  }
  // Capture samples from ADC
  for (int i = 0; i < NUM_SAMPLES; i++) {
    samples[i] = analogRead(SIGNAL_PIN);
    delayMicroseconds(200);  // Sampling rate ≈ 5 kHz
  }

  // Draw waveform on OLED
  display.clearDisplay();
  for (int i = 1; i < NUM_SAMPLES; i++) {
    int x1 = i - 1;
    int y1 = map(samples[i - 1], 0, 1023, SCREEN_HEIGHT - 1, 0);
    int x2 = i;
    int y2 = map(samples[i], 0, 1023, SCREEN_HEIGHT - 1, 0);
    display.drawLine(x1, y1, x2, y2, SSD1306_WHITE);
  }
  display.display();
}