Author Topic: TKL Keyboard - help needed!  (Read 303 times)

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Offline Mcube728

  • Thread Starter
  • Posts: 1
TKL Keyboard - help needed!
« on: Sun, 17 September 2023, 14:52:20 »
Hello Everyone!

I got an cheap old mechanical keyboard(Fullsize ANSI 104) from a friend of mine who wanted to get rid of it due to a few problems regarding ghosting. The switches themselves work fine, and appear to be Cherry MX Blue clones, however there seem to be problems with the PCB, and it looks there are some cuts across the traces on the pcb, and I can't get a replacement pcb for the keyboard. I plan on harvesting the switches from the pcb and make my own tkl keyboard(I'll probably use the numpad switches to make a macropad later, along with a rotary encoder or 2). I need help reviewing the schematics and PCB for for the keyboard(First time designing a keyboard so kinda anxious).

While designing the keyboard, I followed masterzen's keyboard guide. The problem I am facing is that none of the pads on the usb-c port or the MCU have a pad labelled ground, even despite adding multiple grounds in the schematic, so I need reviewing these:

The MCU schema:

The Keyboard Matrix:

The MCU while designing the PCB:

The USB-C port while designing the PCB:

Offline anathae

  • Posts: 2
  • Location: Edmonton, Alberta, Canada
Re: TKL Keyboard - help needed!
« Reply #1 on: Fri, 22 September 2023, 22:44:47 »
On the USB C receptacle that you've chosen, the GND pins are pin 1 and pin 12.  On the ATMega32U4, pins 15, 23, 35, and 43 are GND.  Your circuit shows pin 15 connected to GND.  More than likely, the symbol picked for the MCU has pins 23, 35, and 43 all sitting on top of pin 15, and as such, they are likely all connected to GND.  VCC and +5, in most circuits like this, are the same thing.  The MCU, the ATMega32U4, can operate at +5V, so you could just pick either +5V or VCC, and stick with that.  It might make the circuit a little easier to understand.  I'd also recommend running the trace between pin 2 and 11 underneath the USB C receptacle, On the same side as you have the trace running between the two DP pins, as it removes vias, as well as keeps it from running over top the D+ and D- lines from the receptacle to the MCU.  That last bit might not be a big thing at the speeds that this chip and a USB keyboard communicates with the computer, but it is recommended USB design.