The AVRPi-328 is an Atmel ATmega328p add on board for the Raspberry Pi A+, B+ and 2B. It runs on 3.3V at 8, 12 or 16 MHz (or any other speed you want of course).

All software is easy installable navigating a simple menu. Choose:

• 'e) install everything in 1 easy step'
• 'f) set fuses for atmega328p on avrpi328 board'

That's all it takes to get you started.

Programming and uploading

The ATmega328p can be programmed in the Arduino IDE, but also using the Arduino library and a Makefile, or straight C or assembly. All software that is used on the Pi and the ATmega328 is open source with the source code provided.

AVRPi boards use the latest avrdude-6.1 with the built-in linuxgpio interface.

For more information (pinout, datasheets, soldering) please visit www.onandoffables.com

This board comes as a kit (PCB + all components), and without a Raspberry Pi. Please specify what speed crystal oscillator you want.

What speed should you choose?

• 8 MHz: The most Arduino compatible speed while still being safe. Many Arduinos run on 8 MHz, and you will encounter no problems. All Arduino libraries should be compatible.
• 12 MHz: A nice round number that is close to the maximum speed (13.3 MHz) the ATmega328p can safely run on 3.3V, according to the datasheet. You can't use Arduino's "software serial" at 12 MHz, and possibly some specific libraries will yell at you, but for the most part Arduino works fine.
• 16 MHz: Technically overclocking, but fully Arduino compatible. There are many reports that everything still works fine, but you're advised to use this speed for experimentation only. Don't use it in a real project. The USART may skip a beat once in a while, an ADC reading be off by x values, or the EEPROM messes up a write command. Anything can happen. Nobody knows (it's probably fine, but consider yourself warned).
• Other speeds (bring your own crystal): If you're going to ignore the Arduino library, it may make sense to choose another speed. For example with an 11.0592 MHz crystal, a 0.0% error rate on the USART can be achieved (if that's important to you) while staying within the max speed limit. Or you may choose a speed that gives you the best control over the timers you want to use.

The kit contains

• 1x AVRPi-328 PCB
• All male and female pin headers you need
• Plenty of jumpers (12 pieces)
• 4x 11mm. M2.5 standoffs and 8x 6mm. M2.5 screws
• 1x ATmega328p
• 1x 28 pin IC socket
• 1x 8, 12 or 16MHz crystal oscillator (+ 2x 18pF capacitors)
• 1x green PWR LED
• 1x red USR LED
• 1x tactile button
• 3x 1K resistors
• 1x 10K resistor
• 2x 0.1pF capacitors