July 19: Init, Xiao, and eyeballing

Made a new kicad project. Put a xiao rp2040 on the schematic The idea is that there will be two wings, right and left, connected by a STEMMA QT cable. Right or left wing has the xiao and the right one is just the gesture. We'll be using a PAJ7620U2, or specifically 2x of these. Eyeballing the results on aliexpress show that it has 1x5 2.54mm header rows, 4 are for power, gnd, SDA, and SCL. Not sure what the 5th is for. One thing I was worried about was I2C addresses, since I'm using 2x of one type of sensor which probably uses the same I2C address. I looked stuff up on the datasheets of the RP2040 and Xiao RP2040. The Xiao RP2040 has 1 labeled I2C bus. The RP2040 seems to have two I2C buses that can be assigned to different GPIO. I found two GPIO: GPIO28 and GPIO29 to use for the second I2C bus on the Xiao.

I have yet to eyeball the size of the PAJ7620U2 from Aliexpress

Also need to figure out how to split the PCB into two - one for the left wing and one for the right

Looking for a STEMMA QT footprint on JLCPCB, haven't found one.

Hours: 2.5 roughly, much more spent at night just thinking.

July 20: QWIIC and more eyeballing

I spent a painful amount of time stuff eyeballing the size of a PAJ7620U2 sensor, heres my slack post about it: Yes I'm a dark mode user lol I measured a LOT of things and eyeballed the sensor size, its roughly 15x15mm.

Spent a lot of time wiring QWIIC, asked someone on slack for help with footprints and found a built in one https://www.sparkfun.com/qwiic? I kinda reversed the pinout several times, hope I got it right..

Not sure how I want to manufacture this Definitely via JLCPCB, not sure if I'll use PCBA. LCSC shipping it might be expensive if i have to order the JST SH connectors on the side. (Connectors on the side, please!)

Hours might seem inflated here but I actually spent this much time looking around for the right stuff 😭

I thought about panelization but idk how to do that yet, but if i can do that and get PCBA that might be the best solution. Here I wired up all the QWIIC things which was FUN /halfsarc PCB is okay, routing is all done.

Next I need to panelize and get reading for PCB production. Might make a 3d printed case? idk if the buttons on the xiao might get clicked or not.

Also I was worried about the PAJ7620U2 sensors not working with 3v3 logic and power, so i did a few searches. I found a amazon page that said they could work, so i just have to hope they do :Sob: I also found a confidential datasheet from pixart(i think this is the manufacturer of the actual core sensor) that Seeed Studio leeked, haven't checked what it said about voltages again though.

Anyways very fun and I really enjoyed doing this today

Hours: 4.0 roughly - around 1 in the moring and 3 in the afternoon

July 24: JLCPCB panels

Today I spent like an hour on a support chat with JLCPCB to see if my PCB was manufacturable. I wanted to combine both the mainboard and the wing onto one PCB with mousebites or vscores so i could use PCBA for cheaper, but my luck didn't work out because JLCPCB said it would be charged more.

I also went shopping on aliexpress and I've found the JST SH connectors so I don't need to use PCBA anymore!

Hours: 1

July 25: Rounding, silkscreen PCB wrapup

Spent a LONG time today in kicad Might not look much different, but I spent a really long time trying to figure out how to round corners. I also had to reroute the wing because I messed up. The wing should be better now.

Now I'm writing the BOM :) I should probably make a case but tbh I don't want to. Or maybe I want to, idk sorry

Hours: 2.5