The two QT Py boards will talk to each other over UART serial -- however, in order to simplify wiring and keep it solderless, we'll use the STEMMA QT ports and re-assign the pins that are normally used for I2C to be PIO-based serial pins.
Since the pin assignments are mutable, we'll even be able to get away with a regular cable and avoid having to build a cross-over. The only modification we'll make is to remove the red V+ cable since it isn't necessary and could potentially cause power contention or noise on the serial lines if there are power fluctuations between the two separately powered devices.
Wire Modification
Use a pair of tweezers or dental pick to carefully pry up the connector housing where the red cable connects and extract the red wire from each end.
You'll want to keep the black ground wire and the colored signal wires as is.
Or, make it reeeeally simple and simply cut the red wire near both connector ends. You can even pretend you're defusing the detonator in an 80s action film to make it super exciting! DON'T CUT THE BLUE WIRE!! (or the black or yellow for that matter!)
3D Printed Case
If you'd like to print a case and lid (or have a service do so), the files are below in the blue link. Use PLA with moderate 0.2mm height settings.
Big thanks to the Ruiz Bros. for their cool QT Py case design that I remixed to build this!
Plug 'em In
We know, it looks kinda wacky, but it's gonna be OK we promise! Go ahead and plug the modified STEMMA QT cable into both QT Py boards as shown.
Pop Into Case
Pop the two QT Py boards into the case. Seat each board into place and press fit them in, oriented as shown with their USB C connectors facing out.
Page last edited February 26, 2025
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