Board from here

Wondering if anyone wants to try their hand at tracing this PCB.

http://imgur.com/a/EY5vo (someone else taking apart a different ML board)



Cherry ML switches have four rather than 2 pins. This allows for rows to be continued through the switch if desired, essentially creating a two-layer PCB allowing the manufacturer to only need a one layer PCB. Three pins on the top, one on the bottom. The left and right on the top connect to each other (b pins), the top middle and bottom pin (a pins) are only connected by the switch itself. The a pin between the b pins is connected to them. That is; the three top pins are connected, while the bottom pin is across the switch from them.

Tracing this is actually proving really annoying. There's what you would expect the matrix to be (which is what the imgur album above shows in a different board), and then there's what this board does.











Other teardown

I love these challenges but I have to go to work

After a quick look on my phone it doesn't look very weird - have you tried using the handy row/column grouped pins and standard grid matrix firmware seen what comes out?

I'll be back tonight )

It's probably not actually that bad, but it just doesn't follow any real pattern. It randomly will use the top or bottom pin as the 'entrance' pin, rows/cols in its matrix do not correlate with the physical rows/cols and it uses every possible use case of the 'b' pins.

I'm also still not 100% sure if the b pins are actually connected to the top a pin.

I also haven't spent very long on this, as I'm focusing more on my custom build right now.

/head scratch..

wouldn't it be easier and faster to just make a new layout ?

Not sure what you mean. Use software based key mapping? I could, but that takes the fun out of it.

You have the PCB in hand, right?
Instead of looking at the traces, you could probe the matrix using a multimeter in continuity testing mode. Whenever you have found a match, the multimeter will beep.
If you are doing any kind of electronics, you should have one anyway.

That's what I got as well (will scan my chicken scratch in if there's any interest). Weird that it's an 8x15 matrix to accomplish a 6x16 board though, right?

Was just thinking of that. Highly inefficient IMO.

Especially since the ML jumper lets you thread the columns and rows in a simple grid on one layer of the pcb. This would have been so much cleaner had they done that and used up one fewer i/o pins as well. I just kind of look at this and think, "well, I guess someone must have a reason to do it this way, but damned if I can figure out what."

I can only guess the design is an attempt at anti-ghosting as there are no diodes to be seen, but that usually results in a crazier layout.

That makes more sense that anything I can think of, especially since I can confirm that they did skip including diodes. No idea why they'd skimp out on a couple bucks of diodes on a keyboard that carried a $140 MSRP, but they definitely did.

I wonder if the owner of Genovation Inc still uses one of these, maybe he has his endgame, made his exit, have been using the keyboard for years and until eternity

I don't think anyone would consider these thick pad printed legends end game. They feel so weird.