I’m making a custom keyboard with a Raspberry Pi Pico as the MCU, and i don’t understand what all the different pins are for and how they should be wired up to my key matrix and trackpoint.
My current understanding is that GPIO are normal pins that can be wired to the rows and columns, but what of VBUS, VSYS, 3V3, and all the others that aren’t just GPIO or GND? And how should the ground pins be used here?
The schematic currently doesn’t include the trackpoint because i’m planning to hand wire it and the MCU to the PCB, so i can put them under the PCB in the case and i don’t have to try to fit them onto the board. Is there a better way to connect these that won’t require adding a bunch of space to the board to fit the MCU?
Create ground plane - 1 entire layer for ground. You’ll just use via to connect them
read the data sheet it’ll explain what each pin does. Most of the times single pin can act as multiple things and you need to set certain bit to use certain functions.
for layout fan out from MCU and then on 1 layer try to be horizontal and on another vertical.
when it comes to crowded board vias are both your friends and enemies so use them wisely.
make sure the track length, spacing between track and a via, diameter of via, etc. Are within spec for your manufacturer.
check if any pins are differential pair. If so again adjust your software settings. I think vBUS is a for maybe usb but check datasheet.
You may also want to check out Robert Feranec’s YouTube channel he has some really good videos. Even one on full end to end keyboard design https://www.youtube.com/playlist?list=PLXvLToQzgzdftro2qK5In8p6ExsDFdpzw