23. Custom Functions

This lesson uses: Arduino UNO R3 board, TinkerBlock TK01 XL LED module (or TK02/TK03), jumper wires (or breadboard). Learn custom functions; outcome: wrap “on 200 ms, off 200 ms” in myBlink(), call it from loop, LED blinks at a fixed rhythm.

1. Wiring

Reuse a previous module, e.g. TK01 XL LED:

• GND → Arduino GND
• SIGNAL → Arduino D13
• NC leave unconnected

2. New sketch

1. Arduino IDE: File → New (or Ctrl/Cmd + N) to create a blank sketch
2. Confirm board and port are selected (same as Lesson 01)
3. Type the code below into the default setup() and loop() yourself

3. Program structure

Same as last lesson: two fixed blocks setup() and loop(). We also define our own function.

• Custom function: Wrap repeated code in a named block and call it when needed
• setup(): Tell the board “pin 13 for LED”; runs once
• loop(): Call the custom function so the LED blinks

One “blink” is inside myBlink(); loop just calls it and the LED blinks at a fixed rhythm.

4. Code to write

Define the function before setup() and loop(), then call it inside them:

#define LED_PIN 13   // LED on D13

// Custom function: blink once
void myBlink() {
  digitalWrite(LED_PIN, HIGH);   // On
  delay(200);                    // 200 ms
  digitalWrite(LED_PIN, LOW);    // Off
  delay(200);                    // 200 ms
}

void setup() {
  pinMode(LED_PIN, OUTPUT);   // D13 for LED
}

void loop() {
  myBlink();   // Call custom function: blink once
  delay(500);  // 500 ms before next blink
}

Program notes

Overall idea: Put the four steps “on → delay → off → delay” inside myBlink(); in loop() call myBlink() to run them. void means no return value; call it multiple times for more blinks, or later change to blink(int n) with a parameter.

5. Hands-on

1. After entering the code, click Verify (✓) to compile
2. Click Upload (→) to upload to the board
3. Watch TK01: one quick blink, pause, then another blink, repeat
4. Try yourself:
   • Call myBlink() several times in loop(), e.g. myBlink(); myBlink(); myBlink();
   • Add myBlinkSlow() that blinks slower
   • Try a function with a parameter, e.g. blink(int times) to blink that many times

Expected result: As in the figure.

Proceed to Lesson 24.

6. Common issues

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