I am building a project based on 32u4 MCU that will run on 3,3V and 8MHz.
I made several different designs based on 328p, both on 16MHz and 8MHz while burning the bootloader Nick Gammon provided and it works without any issue. Had zero issues on 2560, too. Can not say enough thanks to him.
But, while reading his list of supported bootloaders on https://www.gammon.com.au/bootloader I noticed there is no support for 3,3V 32u4. So it is not an option.
The Adafruit has its series of Itsy Bitsy 32u4 boards and Feather. Many of them use 32u4 on 8MHz. There is a HEX file that should be used somehow, BUT I don't know how.:)
Can someone provide some links or examples, I would be grateful.
If need, I will provide schematics, but, basically it's just an ICSP header.
Thanks in advance.