Over on the Adafruit forums (https://forums.adafruit.com/viewtopic.php?t=221155) someone asked us to make a QT Py / XIAO board terminal breakout. Good idea! We have loooots of BFFs in the shop (https://www.adafruit.com/category/595) but not one like this, so we spent this morning designing one. We actually tried using an LLM (Claude Opus) to do the design since it's a simple enough thing, worth trying out after our footprint-generation success. But it's still out of reach… the design it came up with was sort of gunky and had weird assumptions and mistakes. All good, we had Claude generate the 7-pin terminal block footprint based on our 9-pin one: a perfect usage since it's a lot of copy-and-paste from a known good outline. The 2x7 SMT headers didn't render here but that's what the QT Py would plug into. Underneath we tucked a LiPo battery backup + charger with auto-fallback to USB, and a Stemma QT connector since most XIAOs don't come with 'em.

Okay, we've got our 1.3" round TFT prototype ready for testing - and here's a cute GIF of a dial turning back and forth. It's a great way to test the display, backlight, and SD card interface. We're using a QT Py ESP32 since we need quite a bit of oomph to decode GIFs and display them in real-time. With EYESPI, no wiring is required! This is good to go - it's time to book the PCB panel!

We designed this CH552-based QT Py to play around with this '40 cent' USB-capable chip, and it's been super fun! now the hardware is complete and assembled, its time to test it so it can go into the shop. we wrote a test sketch in Arduino (https://github.com/DeqingSun/ch55xduino) board support package to verify the GPIO are working right on the pogo bed. the test output goes to the USB serial port which is then read by a python script. to program it, we use the raspberry pi and ch552tool (https://github.com/MarsTechHAN/ch552tool), we can enumerate, test and program the final neopixel swirl in about 10 seconds.

Here's a CAN Bus BFF for any QT or Xiao board. Yes, some QT Py's have ESP32's (https://www.adafruit.com/product/5395) with built-in CAN support but you still need a transceiver (https://www.adafruit.com/product/5708) so we figured we'd just make it easier by popping an MCP25625 which is basically an MCP2515 (https://www.digikey.com/en/products/detail/microchip-technology/MCP2515-I-ST/593002) + MCP2551 (https://www.digikey.com/en/products/detail/microchip-technology/MCP2551T-I-SN/509535) all-in-one chip - probably just wire bonded to a single package. The CS pin is pre-wired, and you can select if you'd like to also access Interrupt, Standby, and Reset pins. To access the CAN wires, use a JST 3-pin cable (https://www.adafruit.com/product/3894): black is ground, red is CAN H, and white is CAN L.

We were recently working on a project where we wanted to power a QT Py ESP32 from 12V - but the only power input on the board was USB 5V max. So here's a quick design we made to allow using these smol boards with up to 20V power! In the center is an MPM3610 integrated buck converter, which will generate 5V from up to 20V input. A 3.5mm terminal block and 2.1mm DC jack inputs are protected with an MBR120 diode. The enable and an extra ground pin are brought out to solderable pads next to the terminal block so you can use a switch to disable the converter. These can give about 1 Amp output, which should be plenty. Since it's a very bulky add-on with through-hole components, it's best to use a socket header to plug a QT Py on top rather than trying to have it solder back-to-back.

Air quality!