so, I'm about to build a custom arduino based on the atmega1284p chip using the sanguino bootloader to work with arduino IDE. I need basic usb to do updates. Doesn't need to be fast just to push commands to the arduino. The ftdi chip can become expensive over time for a large scale project. Saw this and wondered if it has ever been used? Is this implimented at the bootloader level? or as a library for code?

there is a huge limit to 128k chips that can support usb natively and those are the at90usb chips... and sadly the bootloaders for those are not open source. The only other good 128k is the atmega1284p chip so far that I can find that has a open source boot loader.

Why do you need the bootloader to be open source?


I have build several custom boards based on atmega328, but mostly I just implemented an ISP header. I use a programmer to upload my sketches. Only disadvantage so far is that you have no serial output by default. This makes debugging a bit harder. However, you could easily add an additional max232 chip (inexpensive) and wire the tx to an additional pin on your header.

I never use a bootloader.