Running Arduino Code on a Standalone ATmega8

By Prabeesh Keezhathra

- 2 minutes read - 234 words

An Arduino board is essentially an 8-bit Atmel AVR microcontroller with supporting components for easy prototyping. If you have a bare ATmega8 and a USB ISP (like a USBasp or USBtinyISP), you can skip the board entirely and flash sketches straight from the IDE.

What you need

  • A bare ATmega8 chip
  • A USB ISP programmer (USBasp, USBtinyISP, or similar)
  • The Arduino IDE (version 1.0 used here; later versions work too)
  • Optionally, an 8 MHz crystal if you want to use an external clock

IDE setup

  1. Download the IDE and plug in the programmer.
  2. Launch the IDE as root (needed for USB access on some Linux setups).
  3. Under Tools > Programmer, pick your ISP (e.g. USBasp).
  4. Under Tools > Board, select ATmega8.

Fuse-byte configuration

The Arduino runtime assumes an 8 MHz clock. You need the fuse bytes set correctly before uploading any sketch.

For the internal 8 MHz RC oscillator (no crystal required):

1-U lfuse:w:0xa4:m -U hfuse:w:0xcc:m

For an external 8 MHz crystal:

1-U lfuse:w:0xef:m

Once the fuses are set, use Sketch > Upload Using Programmer in the IDE. The sketch compiles, links, and flashes exactly as it would on a real board.

Pin mapping

The ATmega8 pins map to Arduino “digital pin” numbers. Refer to the diagram below when wiring peripherals:

ATmega8 pin mapping

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