Using TXD1/RXD1 on ATmega1280 for USB communication I have a few MakerBot Mightyboards running off ATmega1280 chips that can no longer use their standard USB port to connect to a computer (to make a long story short, there's a little inductor that blew up between the USB port and the 8u2 chip and it is essentially impossible to replace). I have noticed, however, that they have headers for the RXD1 (PD2) and TXD1 (PD3) pins on the 1280 as seen in this picture:



Would it be possible to hook up an external 8u2 (or similar) chip programmed as a USB to serial converter (something like this) and use it as if it were the normal USB port (e.g. for uploading firmware)?

(I wanted to add atmega1280 as a tag, but it doesn't seem to exist)
Not directly, no.

The USB interface connects to TX0 and RX0 - you have access to TX1 and RX1. The bootloader is set to look at TX0 and RX0.

You would have to compile and install a new version of the bootloader that is set to use TX1 and RX1.