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?

  • curbstickle@anarchist.nexusEnglish
    9·
    11 days ago

    So there is a LOT to cover on this, but I’m going to try and keep it to simple overviews.

    • VBUS is the voltage supplied to the device (like 5V from USB)
    • VSYS is the systems voltage that can be supplied from the device to the things its connecting to (like keys)
    • GPIO standards for General Purpose Input / Output, or an uncommitted digital signal pin that can be controlled by the device. It can act as an input or as an output. In a keyboard’s case, this would be predominantly inputs for the keys themselves. If you have RGB LEDs, these would be outputs.
    • ADC VREF is the Analog to Digital Converter Reference Voltage, which is the maximum voltage an ADC can measure and convert to a digital value.
    • 3V3 is 3.3V out
    • 3V3_EN controls the power to the voltage regulator, which lets you shut off the 3.3V supply coming from 3V3
    • RUN is the pin used to start, stop, or reset the microcontroller.
    • AGND is the analog ground, a dedicated ground for the ADC. Its separate from the digital ground (GND) to prevent noise from interfering with analog signals. It eventually connects to the power supply ground though.

    Edited to add: You’ll use GND (ground) shared for all of these keys.