Friday, February 12, 2021

PiPi Gherkin

Gherkin for the Raspberry Pi Pico

Gherkin PCB built specifically for the Raspberry Pi Pico. It has the option of soldering switches directly to the PCB or use sockets. The shape of the PCB and the position of the switches and screw holes are the same as the regular Gherkin, it can use the same top an bottom plates.

I don't really like these sockets, but they are cheap and I won't have to buy as many switches. If you buy in bulk you can get them for as low as $0.08 per piece. That is 1/3 the cost of the cheapest MX switches.

The PCB has the normal solder pads for MX switches in one orientation and the sockets in the other.

The PiPi Gherkin PCB fits in the old Gherkin top/bottom PCB plates.

M2 spacers and screws.

I used 13mm M2 spacers, 12mm should also be enough to clear the USB connector on the Raspberry Pi Pico.

Micro USB connector of the Raspberry Pi Pico.

Separated, switches can now be used in something else.

All of the pins on the Raspberry Pi Pico are broken out to pads. The pins used for the matrix are listed here, the rest can be used for other things.

It is possible to construct it plateless. The pads for the sockets come very close but do not touch regular cheap M2 spacers.

Nylon M3 spacers fit over the M2 spacer.

Plateless works with PCB mount switches. There isn't much holding the switches in place other than the friction fit of the PCB mount pins and the sockets.

8mm spacers, 7mm should also be tall enough.

This is running KMK with this config file. The current release version of KMK will need the file modified as described here.

Gerber files on git.

Wednesday, February 3, 2021


Carrier board for KMK experimenting

Three different KMK compatible MCU boards can be plugged into this board with a 12x4 key matrix of 6x6mm tactile switches.

The ESP32-S2 Saola board was the primary reason for this board. The micro USB connector is not the USB HID interface. Pins 19/20 are USB -/+. These are connected to the mini USB connector.

The narrower Raspberry Pi Pico fits inside the ESP32-S2 Saola footprint. You will need to modify the KMK as described here.

The Adafruit NRF52840 Express takes up the remaining space. The Adafruit NRF52840 also works over BLE if enabled (USB or BLE, not both).

All three MCU run the same KMK script. The only differences are the board pin definitions.

Gerber files on git.