/*
  3D Photogrammetry Scanner Controller
  Hardware: Arduino Nano, L298N Stepper Driver, Mitsumi Stepper,
            2SC1740 NPN switching a 150 ohm resistor across the phone's
            mic/ground pair (2.15k detect resistor sits permanently across
            the same pair, at the jack).

  Pin Out Summary:
  - D2:  Button 1 (4-Photo Quick Scan)  -> GND
  - D3:  Button 2 (36-Photo Full Scan)  -> GND
  - D4:  Transistor base (via 987 ohm)  -> camera shutter
  - D5:  Button 3 (Continuous Showcase) -> GND
  - D8:  L298N IN1
  - D9:  L298N IN2
  - D10: L298N IN3
  - D11: L298N IN4
  - D12: L298N ENA/ENB

  SETUP ORDER: power the Arduino first, then plug the phone in, then open
  the camera app. There is no base pulldown fitted, so D4 floats for ~1-2 s
  during boot and can trigger a spurious shot if the phone is already
  connected.
*/

// --- Pin Definitions ---
const int BTN_4_PHOTO  = 2;
const int BTN_36_PHOTO = 3;
const int SHUTTER_PIN  = 4;
const int BTN_SHOWCASE = 5;

const int IN1 = 8;
const int IN2 = 9;
const int IN3 = 10;
const int IN4 = 11;
const int ENABLE_PIN = 12;

// --- Timing (tune these) ---
// SHUTTER_MS must be long enough for the phone to register the press but
// short enough to stay below the camera app's burst threshold. Find the
// burst threshold by hand, then use about half of it.
const int SHUTTER_MS = 120;

// Time for the turntable to stop oscillating after a move. Start high,
// walk it down while checking images at 100% zoom until blur appears.
const int SETTLE_MS = 800;

// Time for the phone to capture and write the file before we move again.
const int CAPTURE_MS = 2200;

const int STEP_DELAY_US = 12000;      // scan speed
const int SHOWCASE_DELAY_US = 8000;   // showcase spin speed

// Release the coils while waiting, to keep the motor cool. The 11:1
// reduction means there is effectively no backdrive. Set false if you see
// the table creep between positions.
const bool RELEASE_COILS_WHEN_IDLE = true;

// --- Stepper Motor Parameters ---
const int STEPS_PER_REV = 48;   // Mitsumi 7.5-degree step angle
const float GEAR_RATIO = 11.0;  // 176 ring teeth / 16 spur teeth
const long TOTAL_STEPS = (long)(STEPS_PER_REV * GEAR_RATIO);  // 528

// Stepper Sequence (Full Step Mode)
const int stepMatrix[4][4] = {
  {HIGH, LOW,  HIGH, LOW},
  {LOW,  HIGH, HIGH, LOW},
  {LOW,  HIGH, LOW,  HIGH},
  {HIGH, LOW,  LOW,  HIGH}
};

int stepIndex = 0;

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(ENABLE_PIN, OUTPUT);

  pinMode(SHUTTER_PIN, OUTPUT);
  digitalWrite(SHUTTER_PIN, LOW);   // transistor off before anything else

  pinMode(BTN_4_PHOTO, INPUT_PULLUP);
  pinMode(BTN_36_PHOTO, INPUT_PULLUP);
  pinMode(BTN_SHOWCASE, INPUT_PULLUP);

  disableMotor();
}

void loop() {
  if (pressed(BTN_4_PHOTO)) {
    runScanSequence(4);
    waitForRelease(BTN_4_PHOTO);
  }

  if (pressed(BTN_36_PHOTO)) {
    runScanSequence(36);
    waitForRelease(BTN_36_PHOTO);
  }

  if (pressed(BTN_SHOWCASE)) {
    waitForRelease(BTN_SHOWCASE);
    runShowcaseMode();
  }
}

// --- Photogrammetry Scan Sequence ---
// Shoots at position 0 first, then moves-settles-shoots for the rest, and
// returns home at the end. Positions are computed absolutely so rounding
// never accumulates: 36 photos still covers a full 528-step revolution.
void runScanSequence(int photoCount) {
  long previous = 0;

  triggerShutter();
  delay(CAPTURE_MS);

  for (int i = 1; i < photoCount; i++) {
    long target = ((long)i * TOTAL_STEPS) / photoCount;

    enableMotor();
    moveSteps(target - previous, STEP_DELAY_US);
    if (RELEASE_COILS_WHEN_IDLE) disableMotor();
    previous = target;

    delay(SETTLE_MS);
    triggerShutter();
    delay(CAPTURE_MS);
  }

  // Return to the starting position
  enableMotor();
  moveSteps(TOTAL_STEPS - previous, STEP_DELAY_US);
  disableMotor();
}

// --- Showcase / Presentation Continuous Rotation ---
void runShowcaseMode() {
  enableMotor();
  delay(200);

  while (true) {
    stepMotor(1);
    delayMicroseconds(SHOWCASE_DELAY_US);

    if (pressed(BTN_SHOWCASE)) {
      waitForRelease(BTN_SHOWCASE);
      break;
    }
  }

  disableMotor();
}

// --- Helper Functions ---

bool pressed(int pin) {
  if (digitalRead(pin) != LOW) return false;
  delay(50);                        // debounce
  return digitalRead(pin) == LOW;
}

void waitForRelease(int pin) {
  while (digitalRead(pin) == LOW) delay(10);
  delay(50);                        // debounce the release
}

void triggerShutter() {
  digitalWrite(SHUTTER_PIN, HIGH);  // 150 ohm across mic/gnd -> volume up
  delay(SHUTTER_MS);
  digitalWrite(SHUTTER_PIN, LOW);
}

void moveSteps(long steps, int speedDelayUs) {
  for (long i = 0; i < steps; i++) {
    stepMotor(1);
    delayMicroseconds(speedDelayUs);
  }
}

void stepMotor(int dir) {
  stepIndex += dir;
  if (stepIndex > 3) stepIndex = 0;
  if (stepIndex < 0) stepIndex = 3;

  digitalWrite(IN1, stepMatrix[stepIndex][0]);
  digitalWrite(IN2, stepMatrix[stepIndex][1]);
  digitalWrite(IN3, stepMatrix[stepIndex][2]);
  digitalWrite(IN4, stepMatrix[stepIndex][3]);
}

void enableMotor() {
  digitalWrite(ENABLE_PIN, HIGH);
}

void disableMotor() {
  digitalWrite(ENABLE_PIN, LOW);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}