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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:

PD0-PD3 pins on Mightyboard Rev H

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)

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    How on earth did you manage to blow up a resistor?!?!?!
    – Majenko ♦
    Apr 2, 2018 at 10:37
  • Just noticed I actually got mixed up and the parts I'm talking about are inductors. They're tiny surface-mounted ones, and they're placed right next to the USB port. The boards are quite old (about 5 years) so I'm guessing a slight power surge over USB caused them to literally blow up (there's burn marks on the boards that have this).
    – Nicolas Gnyra
    Apr 2, 2018 at 16:34

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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.

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  • Thanks! I highly doubted it would work out-of-the-box like that. Do you happen to know what changes I would have to make to the bootloader for this to work (and where I could get said bootloader)?
    – Nicolas Gnyra
    Apr 2, 2018 at 17:36
  • No idea, I have never compiled the bootloader. I think there's something included with the IDE somewhere. Or Google optiboot as an option.
    – Majenko ♦
    Apr 2, 2018 at 17:54
  • Alright, I'll try that out. It might take a while though since I'm waiting on parts. I'll make sure to post any new info I might have.
    – Nicolas Gnyra
    Apr 2, 2018 at 18:05

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