I have recently designed a STM32G071CB-based board that, when paired with right TPS65982 config, can provide access to Librem 5’s UART2 serial over its USB-C port in a plug-and-play manner while still allowing to use the phone’s USB-C port for power and USB 2.0 data.
Looking forward to the merge request into master and its subsequent firmware update.
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The only thing changed in that merge request is alt-mode config that can be used by Debubo to automatically enable Thunderbolt mode, which muxes UART2 into SBU pins. There’s no rush to merge it, if you need it today already you can just grab the file from MR. You can also enable it manually instead, as described at Serial Console · Wiki · Librem5 / Librem 5 Community Wiki · GitLab.
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Debubo GitLab repository:
Any chance of it being sold in the Purism shop similar to the EXT CON Breakout Board?
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It’s a GPLv3+ design, so nothing prevents it from happening. You’ll have to ask Purism though, I did my part on my own as a hobby project.
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For those interested, I’ve pushed the firmware that implements the necessary alt-mode dance to get UART out of the Librem 5 to Debubo’s repository.
It wasn’t pushed before because it was very crude and I wanted to clean it up before pushing. It still is, but I decided to actually get it out regardless rather than risk having it sit and wait for many more months 
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