You happen to have an Arduino Nano laying around, and wanted to program some AVRs but don’t have an AVRISP programmer?
No worries. If you use the Arduino IDE, then you can opt for the built-in example, the 11.ArduinoISP. This out-of-the-box option is certainly useful for a lot of people, however it has some shortcomings. Like you need to use the Arduino ecosystem -which makes your compiled code big- with the bundled compiler toolchain. Also the ArduinoISP is slow, it uses 19.200 kbps for the serial communication with your computer. Also, it uses a fixed SPI clock -which cannot be changed dynamically at runtime-, which can be too fast for targets running at low frequencies.
Since these shortcomings were not suitable for my application, and I wanted to learn some AVR assembly, the project avrispm328p was born.
It turns your ATmega328P-based board (like an Arduino Nano, Uno, etc.) into an AVR ISP with adjustable SCK half-period, using the STK500v1 protocol.
It’s open-source and free, check it out on GitHub!
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