DocsOpen the editorEditor
Built-in project · Arduino Micro

Micro blink

The Arduino Micro’s RX lamp, which lights when its pin goes low, blinking beside an LED on pin 9 that lights when it goes high. The whole build, an Arduino Micro and 2 more parts, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

Open in the editorRead the code

Runs in your browser. Free, and no account needed.

Micro blink · Arduino Microlive0.000 s 0.00x
Click to open it in the editor
The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The firmware exactly as the editor opens it. Change a line there and press Run: it compiles in the browser.

sketch.ino · Arduino Micro
// RX blink: the lamp a board with no pin 13 still has.
//
// Every ATmega32U4 board has an RX and a TX LED, and both are wired from 5 V
// through a resistor to a pin: RX to PB0, TX to PD5. So the pin has to go LOW
// to light one. RXLED1 does that and RXLED0 lets it go dark again.
//
// On a Leonardo or a Micro this blinks the RX lamp beside L. On a SparkFun Pro
// Micro, which does not bring pin 13 out at all, it is the only way to see a
// blink without wiring anything: LED_BUILTIN is still 13 there, and blinking
// it lights nothing.
//
// Pin 9 blinks at the same time the ordinary way round, HIGH for on, so an
// LED and a resistor from pin 9 to GND show the difference side by side.

const int WIRED = 9;

void setup() {
  TX_RX_LED_INIT;
  TXLED0;
  pinMode(WIRED, OUTPUT);
}

void loop() {
  RXLED1;                     // lamp on: PB0 low
  digitalWrite(WIRED, HIGH);  // wired LED on: pin 9 high
  delay(500);
  RXLED0;                     // lamp off: PB0 high
  digitalWrite(WIRED, LOW);
  delay(500);
}

Parts list

4 parts, plus the jumper wires. Every one is in the editor's parts bin.

How it is wired

3 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.

  • Arduino Micro pin 9; Resistor, 220 Ω pin 1
  • Ground: Arduino Micro pin GND; LED, red pin C
  • Resistor, 220 Ω pin 2; LED, red pin A

Change it and keep it

Open it in the editor, change the circuit or the code, and keep your version in a free account.

Create a free account
Open it in the editor