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Built-in project · ATmega328P, 16 MHz crystal

ATmega328P on a breadboard

The Uno’s chip on its own in a breadboard, wired as the tutorial wires it: 5 V on VCC and AVCC, both grounds, RESET held high, and an LED on PB5, which is pin 13 in code. The whole build, an ATmega328P on a breadboard and 3 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.

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The parts retail for about $8.20. On Mokxi they're free.

ATmega328P on a breadboard · ATmega328P, 16 MHz crystallive0.000 s 0.00x
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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 · ATmega328P, 16 MHz crystal
// Blink: the smallest thing a board can do.
//
// Pin 13 has the LED soldered next to the USB socket, so LED_BUILTIN is 13.
// Wire an LED and a 220 ohm resistor from pin 13 to GND to see it on the
// breadboard too.
//
// delay() puts the chip to sleep between timer ticks rather than spinning, so
// this sketch costs the simulator almost nothing while it waits.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
}

Parts list

6 parts, plus the jumper wires. They retail for about $8.20; on Mokxi they're free.

How it is wired

5 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.

  • 5 V: ATmega328P, 16 MHz crystal pin VCC; ATmega328P, 16 MHz crystal pin AVCC; Resistor, 10k Ω pin 1
  • Ground: ATmega328P, 16 MHz crystal pin GND; ATmega328P, 16 MHz crystal pin GND; LED, red pin C
  • ATmega328P, 16 MHz crystal pin RESET; Resistor, 10k Ω pin 2
  • ATmega328P, 16 MHz crystal pin PB5; Resistor, 220 Ω pin 1
  • Resistor, 220 Ω pin 2; LED, red pin A

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