/*
  4-Channel Relay Module — Combined Sample Sketch
  Tishvi Docs · guide.tishvi.com

  Wiring (Arduino UNO R3):
    Relay VCC  -> Arduino 5V
    Relay GND  -> Arduino GND
    Relay IN1  -> Arduino D2   (controls K1)
    Relay IN2  -> Arduino D3   (controls K2)
    Relay IN3  -> Arduino D4   (controls K3)
    Relay IN4  -> Arduino D5   (controls K4)

  JD-VCC jumper: leave installed for this sketch (single 5V supply powers
  both the logic side and the relay coils). Remove it only if you're
  powering the coils from a separate 5V supply — see the guide's
  "Understanding the JD-VCC Jumper" section.

  Output wiring (per channel, screw terminals):
    COM -> one side of your load's power source
    NO  -> the load, for "on when triggered" behaviour (most common)
    NC  -> the load, for "on until triggered" fail-safe behaviour

  SAFETY: This module can switch up to 250V AC / 10A. Disconnect mains
  power before wiring or rewiring the output side. Test with a low-voltage
  DC load (e.g. a 12V lamp on its own supply) before working with mains.

  Trigger polarity:
    Most boards built with this layout (opto-isolator + transistor driver,
    D1-D4 status LEDs) are LOW-level triggered — LOW on an IN pin turns
    that relay ON. If your relays behave the opposite way, set
    RELAY_ACTIVE_LOW to false below.

  What it does:
    - On startup, runs a quick cycle test: K1 -> K2 -> K3 -> K4, one at a
      time, so you can confirm wiring and polarity.
    - After that, listens on Serial Monitor for '1', '2', '3', or '4' to
      toggle that channel individually.

  Baud rate: 9600. No external libraries needed.
*/

const int relayPins[4] = {2, 3, 4, 5}; // IN1..IN4
bool relayState[4] = {false, false, false, false};

// Flip to false if your board's relays trigger backwards from what you expect.
const bool RELAY_ACTIVE_LOW = true;

void relayWrite(int pin, bool on) {
  bool level = RELAY_ACTIVE_LOW ? !on : on;
  digitalWrite(pin, level ? HIGH : LOW);
}

void setup() {
  Serial.begin(9600);

  // Set every relay OFF immediately, before anything else runs, so a
  // briefly-floating pin during boot can't flash a relay on.
  for (int i = 0; i < 4; i++) {
    pinMode(relayPins[i], OUTPUT);
    relayWrite(relayPins[i], false);
  }

  Serial.println("4-Channel Relay Module ready.");
  Serial.println("Running cycle test: K1 -> K2 -> K3 -> K4...");

  for (int i = 0; i < 4; i++) {
    Serial.print("K");
    Serial.print(i + 1);
    Serial.println(" ON");
    relayWrite(relayPins[i], true);
    delay(1000);
    relayWrite(relayPins[i], false);
    delay(300);
  }

  Serial.println("Cycle test done. Send 1, 2, 3, or 4 to toggle a relay.");
}

void loop() {
  if (Serial.available()) {
    char c = Serial.read();
    if (c >= '1' && c <= '4') {
      int idx = c - '1';
      relayState[idx] = !relayState[idx];
      relayWrite(relayPins[idx], relayState[idx]);

      Serial.print("K");
      Serial.print(idx + 1);
      Serial.println(relayState[idx] ? " -> ON" : " -> OFF");
    }
  }
}