#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);

#define SIGNAL_PIN A0
#define PULSE_PIN 9

#define POT_TIME A1      // Potentiometer for time scaling
#define POT_AMP  A2      // Potentiometer for amplitude scaling
const int stopButton = 7; // Stop / Freeze button (active LOW)

#define NUM_SAMPLES 128
int samples[NUM_SAMPLES];   // stores last captured waveform

void setup() {
  pinMode(PULSE_PIN, OUTPUT);
  tone(PULSE_PIN, 100);   // Generate 100 Hz test square wave

  pinMode(stopButton, INPUT_PULLUP);  // button with pull-up

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    for (;;);
  }
  display.clearDisplay();
  display.display();
}

void loop() {
  // --- Read pots ---
  int potTime = analogRead(POT_TIME);   // 0–1023
  int potAmp  = analogRead(POT_AMP);    // 0–1023

  // Map potentiometers
  int sampleDelay = map(potTime, 0, 1023, 20, 2000);     // µs per sample
  float ampScale  = map(potAmp, 0, 1023, .5, 10) / 10.0;  // 0.5x – 2.0x amplitude

  // --- Capture waveform only if NOT stopped ---
  if (digitalRead(stopButton) == HIGH) {  // HIGH = running
    for (int i = 0; i < NUM_SAMPLES; i++) {
      samples[i] = analogRead(SIGNAL_PIN);
      delayMicroseconds(sampleDelay);
    }
  }

  // --- Always redraw (so scaling pots work while frozen) ---
  display.clearDisplay();
  for (int x = 1; x < NUM_SAMPLES; x++) {
    int y1 = map(samples[x - 1], 0, 1023, SCREEN_HEIGHT - 1, 0);
    int y2 = map(samples[x], 0, 1023, SCREEN_HEIGHT - 1, 0);

    // Apply amplitude scaling around vertical center
    y1 = (SCREEN_HEIGHT / 2) + (y1 - SCREEN_HEIGHT / 2) * ampScale;
    y2 = (SCREEN_HEIGHT / 2) + (y2 - SCREEN_HEIGHT / 2) * ampScale;

    y1 = constrain(y1, 0, SCREEN_HEIGHT - 1);
    y2 = constrain(y2, 0, SCREEN_HEIGHT - 1);

    display.drawLine(x - 1, y1, x, y2, SSD1306_WHITE);
  }

  // --- Display info text ---
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.print("T:");
  display.print(sampleDelay);
  display.print("us");

  display.setCursor(70, 0);
  display.print("A:");
  display.print(ampScale, 1);
  display.print("x");

  if (digitalRead(stopButton) == LOW) {
    display.setCursor(100, 0);
    display.print("STOP");
  }

  display.display();
}