Request for help 'debugging' the pcb

[MvRoo]

Hi,

Thanks for the great guide and all the time you've invested in creating and sharing it!

I've tried to build the choc+rpi2040 build, but unfortunately, I am having issues with getting certain keys registered. The right hand side of my build doesn't work at all and for the left hand side I managed to figure out that all the keys in a single row are not working. I'm not sure how you have designated the rows, but can tell you that key3, key7, key11, key20 and key22 are not working. I am not sure how to tell, from the schematic or the pcb design, to which IO pin the row should connect. I am also entirely unclear how I can read the schematic to understand the right hand side of the keyboard.

Any pointers would be greatly appreciated!

Ps. I opened the project in kicad

Regards,
Michael

[nmunnich]

Hi there, the build guide includes some images to help you debug such issues with a multimeter. You'll want to check continuity between each side of the diode and the corresponding MCU pin while the faulty switch is closed. Without a multimeter I would consider debugging DIY electronics projects an exercise in frustration and probably also futility. Most likely you have some faulty solder joints on the left half, and my guess for the right half would be that you missed closing the jumpers, maybe?

The schematic and PCB are very annoying to understand, hence why I created the images.

[MvRoo]

Hi @nmunnich , thanks for the reply! This will already help me check some things. Yesterday evening, I got a bit further in understanding how the traces for these keys run and to which MCU pin they connect, based on the schematic and the PCB. I have a multimeter and I used it already to do some testing after soldering the diodes based on the images you created. I thought all was working well, even though in some cases the beep was not continuous, which might have been a clue already. I am doing all of this for the first time, so it was to be expected that everything wouldn't work in one go.

Thanks for creating the pictures of the traces; they are indeed easier to understand than the PCB in Kicad. Jumping into the schematic and PCB in Kicad also increased my understanding of the pictures. One thing I still don't understand, though: why are some lines red and black?

[nmunnich]

Some lines are red and black purely to ease following them visually. When they were all black it was hard to not mix them up, so I added some colours.

[MvRoo]

Update: I wasn't able to figure out what is wrong exactly, using a multimeter and the traces picture; it could be traces on the PCB or faulty solder joints or something completely different, no clue. I decided to start fresh with a new pcb for the left half and use a different approach to soldering the diodes. I am happy to report the left half now works as designed! Now I will need to redo the right half...

[RaveGun]

Hi,

I had a similar issue at the beginning with one of my build too, the delivered SMD diodes were mixed up. I had 2 different types with different forward voltage. Once I swapped all of them from 0,8V with 0,6V, it worked all fine up to one small issue.

Correction: What I wrote down here is not correct. I opened up the case on both types to do some measurement and all works well. So in my case it must be something with the case / pressure / not fitting properly, don't know. From what I can tell once removed from the bottom part, it works fine. I am typing these lines using the choc variant.

Both builds, one slim with Choc and SMD diodes, and one MX with THT diodes are registering the O and 0 multiple times or not at all on short presses. Both are with the XIAO MCUs + XIAO dongle.

I hope it helps.