Standalone Atmega328P guide

2022-09-12
electronics, Arduino

This guide describes how to burn a program into an Atmega328P microcontroller, using an Arduino board as programmer and an external 16MHz oscillator. It's the result of the frustration that every single time I wanted to to this, it was a struggle because I couldn't find any complete tutorial. At least, the following works for me.

#Materials needed

• Atmega328P (the P matters)
• Arduino board (I used an Arduino Micro)
• 16MHz oscillator
• 2× 22pF capacitors
• 10kΩ resistor
• 100µF capacitor

#Notes

If you don't have any 22pF capacitor, you can salvage some capacitors from an old device (e.g. there are plenty in videotape readers). Unfortunately through-hole capacitors with this value look pretty rare, so you may need to salvage a bunch of unmarked surface-mounted ones and build a simple Arduino-based capacitance meter to find the wanted ones.

#Circuit

Check Atmega328P's pinout in the datasheet.

• Connect the MOSI, MISO, SCK(=SCLK) pins on the Arduino to the corresponding ones on the Atmega. (on Arduino Uno, they are respectively on pins 11, 12, 13)
• Connect Arduino pin 10 to Atmega's Reset pin.
• Connect each pin on the oscillator to the XTAL/TOSC pins on the Atmega, and place a 22pF capacitor between each of these two pins and the GND.
• Connect the GNDs together. Connect Atmega's VCC, Atmega's AVCC and Arduino's +5V together.

Triple-check the wiring. MOSI goes on MOSI and MISO goes on MISO, they are not swapped.

#For normal operation

The following connections are only needed when the microcontroller is disconnected from the Arduino.

• Place a pull-up resistor on the Reset pin (10kΩ resistor between Reset and VCC).
• Place a 100µF capacitor between GND and VCC.
• The oscillator and ceramic capacitors are still needed.
• VCC and AVCC still have to be connected.

#Program

I'm using the Arduino IDE.

First, we program the Arduino board to make it operating as a relay between the computer and the microcontroller:

1. Open the example sketch ArduinoISP.
2. If using an Arduino Uno, uncomment the line #define USE_OLD_STYLE_WIRING.
3. Choose your programmer board as board type (Arduino Micro in my case).
4. Choose a regular programmer (typically AVR ISP).
5. Upload the sketch normally.

Now we can program the microcontroller:

1. Open the wanted sketch. (or start with the Blink example)
2. Choose Arduino Uno as board type. (even if you're using another board as a programmer; it's because a standalone Atmega328P with a 16MHz oscillator behaves like an Arduino Uno)
3. Choose Arduino as ISP as programmer.
4. If your microcontroller doesn't contain a bootloader yet, upload the bootloader using Tools -> Burn bootloader.
5. Upload the sketch using Sketch -> Upload using programmer.