Atmega328 20MHz on breadboard.

Hi

Could I: -instal the 16MHz bootloader, -use the arduino board to upload programs via USB, -then have MCU run off the arduino board using a 20MHz crystal?

I don't care is if the baud rate is incorrect because I am not using the UART, just I2C which is not frequency dependent.

Thanks

It will work.

But maybe using Arduino as ISP is more convenient way unless you wamt somedebugging while in the Arduino board.

Why don’t just use a 20 MHz bootloader, so that the baudrate and time keeping will be 100% correct?

You’ll find all necessary information here :slight_smile:
https://github.com/MCUdude/MiniCore