reTerminal GPIO header GPIO13 conflict with USB hub

In addition to being mounted backwards (which is noted elsewhere) the pinout for the GPIO header on the reTerminal appears to stray from the standard Raspberry Pi pinout. Specifically, pins 31 and 33, which should be GPIO6 and GPIO13 respectively, are connected to port 3 of the USB hub (HUB_DM3/HUB_DP3 respectively). This means pin 33 can’t be used as RXD5 (or anything else) so UART5 can only transmit, not receive. From the schematic it looks like this is just the way it is but maybe I’m missing something. Is it possible to properly map these pins to GPIO6 and GPIO13 as RPi intended?

Yeah, you’re right. According to the schematic, GPIO6 and GPIO13 inside the reTerminal 40pin are indeed used as a USB Hub. so you can’t use those two GPIO ports.

I solved my own question, so for anyone else who really needs UART5 to work properly here’s what you have to do (it involves removing parts and adding a jumper to the reTerminal, so proceed at your own risk):
1) remove R198
2) remove R282
3) remove Q21
4) add jumper from Q21.3 to J7.33 (40 pin header)

The power button will still be able to turn the reTerminal on but it won’t be able to turn it off so you’ll need to shut it off in software (sudo halt). Ideally the reTerminal’s device tree overlay would be updated but it’s not necessary. Add “dtoverlay=uart5” to /boot/config.txt to enable uart5 on GPIO12 (Tx) and 13 (Rx). The board doesn’t have reference designators on most parts and this forum doesn’t allow links so you’re pretty much on your own figuring out which parts are which. You have to track them down using the reTerminal schematic. I have tested this and it works fine.

Hope someone finds this helpful.


Hi there,
WOW , Good job… Looks like an edit to the wiki is in order too.
I LOL that some call this “open source” IMO if there’s no Schematic available, no factory type reset image or even Doc’s for the images that it ships with kinda makes the point. It’s a Great Idea and platform but falls short on delivering the “Full Monty” experience.
I always thought it to be the big brother to the WIO terminal, but it’s not that OPEN.
GL :slight_smile: PJ

I’m certain folks will find the info usable for sure :+1:

The schematic is out there on the seeedstudio web site; I’d link to it but I can’t since the forum doesn’t allow links. Google “seeed reterminal schematic” and it should be the first hit. Follow the trace from J7.33 to find R198. Q21 is on the opposite end and is one of the few SOT-23 parts so it isn’t super hard to find (near the marking “PWR”). R282 is right in front of Q21’s pin 3.

The code is on GitHub, so if you cared you could patch the device tree overlay to not use GPIO13 for sensing the power switch but the pulses from the UART are too short to register as switch closures so it works okay even if you don’t bother to fix and rebuild the overlay. The ISO is available, too, I had to re-flash one when I screwed something up. I’d be happier if the 40-pin header actually matched the Pi 100% (and wasn’t backwards) but overall I’m still pretty impressed with the reTerminal and find it very useful.

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