Arduino Digital Tempo Controller

tap_tempo.ino

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// --- LCD Setup ---
LiquidCrystal_I2C lcd(0x27, 20, 4);  // 20x4 LCD at address 0x27

// --- Pins ---
const int ENC_CLK = 2;   // Encoder A (interrupt)
const int ENC_DT = 3;    // Encoder B
const int ENC_SW = 10;   // Encoder push button
const int SW2_PIN = 11;  // Step size switch 1
const int SW1_PIN = 12;  // Step size switch 2
const int TAP_OUT = 13;  // Tap tempo output (to pedal)

const unsigned long MIN_DELAY = 67;
const unsigned long MAX_DELAY = 10000;
unsigned long delay_ms = 450;

volatile int encoderDirection = 0;
volatile bool encoderMoved = false;

bool synced = true;
unsigned long lastEncoderActivity = 0;
int stepSize = 1;

// Tap control
bool tapInProgress = false;
unsigned long tapTimer = 0;
int tapStage = 0;

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Setup pins
  pinMode(ENC_CLK, INPUT_PULLUP);
  pinMode(ENC_DT, INPUT_PULLUP);
  pinMode(ENC_SW, INPUT_PULLUP);
  pinMode(SW1_PIN, INPUT_PULLUP);
  pinMode(SW2_PIN, INPUT_PULLUP);
  pinMode(TAP_OUT, OUTPUT);
  digitalWrite(TAP_OUT, LOW);

  // Setup encoder interrupt
  attachInterrupt(digitalPinToInterrupt(ENC_CLK), encoderISR, FALLING);

  updateStepSize();
  updateDisplay();
}

void loop() {
  unsigned long now = millis();

  // Update step size if needed
  static bool lastSW1 = HIGH;
  static bool lastSW2 = HIGH;
  bool currSW1 = digitalRead(SW1_PIN);
  bool currSW2 = digitalRead(SW2_PIN);
  if (currSW1 != lastSW1 || currSW2 != lastSW2) {
    updateStepSize();
    updateDisplay();
    lastSW1 = currSW1;
    lastSW2 = currSW2;
  }

  // Handle encoder movement
  if (encoderMoved) {
    encoderMoved = false;
    lastEncoderActivity = now;
    synced = false;

    if (encoderDirection > 0) {
      delay_ms = min(delay_ms + stepSize, MAX_DELAY);
    } else if (encoderDirection < 0) {
      delay_ms = max(delay_ms - stepSize, MIN_DELAY);
    }

    updateDisplay();
  }

  // Check pushbutton (encoder press)
  static bool lastButtonState = HIGH;
  bool currButtonState = digitalRead(ENC_SW);

  if (lastButtonState == HIGH && currButtonState == LOW) {
    requestTap();
  }
  lastButtonState = currButtonState;

  // Handle tap state machine
  if (tapInProgress) {
    handleTap(now);
  }
}

void encoderISR() {
  if (digitalRead(ENC_DT) == LOW) {
    encoderDirection = -1;  // CCW
  } else {
    encoderDirection = 1;  // CW
  }
  encoderMoved = true;
}

void updateStepSize() {
  bool s1 = digitalRead(SW1_PIN) == LOW;
  bool s2 = digitalRead(SW2_PIN) == LOW;

  if (!s1 && !s2) {
    stepSize = 10;
  } else if (s1 && !s2) {
    stepSize = 1;
  } else if (!s1 && s2) {
    stepSize = 100;
  }
}

void updateDisplay() {
  lcd.clear();

  // Line 1: Tempo Controller (centered)
  lcd.setCursor(0, 0);
  lcd.print(centerText("Tempo Controller"));

  // Line 2: Delay ms (centered)
  lcd.setCursor(0, 1);
  String delayText = String(delay_ms) + " ms";
  lcd.print(centerText(delayText));

  // Line 3: SYNCED / *UNSYNCED* (centered)
  lcd.setCursor(0, 2);
  String statusText = synced ? "SYNCED" : "*UNSYNCED*";
  lcd.print(centerText(statusText));

  // Line 4: Step info (left and right aligned)
  lcd.setCursor(0, 3);
  lcd.print("Step:");
  String stepText = String(stepSize) + " ms";
  lcd.setCursor(20 - stepText.length(), 3);
  lcd.print(stepText);
}

String centerText(String text) {
  int spaces = (20 - text.length()) / 2;
  String result = "";
  for (int i = 0; i < spaces; i++) {
    result += " ";
  }
  result += text;
  return result;
}

void requestTap() {
  if (tapInProgress) return;
  tapInProgress = true;
  tapStage = 1;
  tapTimer = millis();
}

void handleTap(unsigned long now) {
  switch (tapStage) {
    case 1:  // Tap 1 ON
      digitalWrite(TAP_OUT, HIGH);
      tapStage = 2;
      tapTimer = now + 50;
      break;
    case 2:  // Tap 1 OFF
      if (now >= tapTimer) {
        digitalWrite(TAP_OUT, LOW);
        tapStage = 3;
        tapTimer = now + (delay_ms - 50);
      }
      break;
    case 3:  // Tap 2 ON
      if (now >= tapTimer) {
        digitalWrite(TAP_OUT, HIGH);
        tapStage = 4;
        tapTimer = now + 50;
      }
      break;
    case 4:  // Tap 2 OFF
      if (now >= tapTimer) {
        digitalWrite(TAP_OUT, LOW);
        tapInProgress = false;
        synced = true;
        updateDisplay();
      }
      break;
  }
}