The PB Gherkin is a "30% Keyboard", indicating that it has 30 keys (about 30% of the number of keys on a classic PC keyboard). This can be a challenging keyboard to use, since the keyboard layout is organized in "layers". However, it's a comparatively inexpensive way to enter the world of hand-soldered custom keyboards!

This keyboard is designed for a "pro micro" microcontroller board. The Adafruit KB2040 is in the same form factor, and QMK can automatically convert a "pro micro" keyboard firmware to work on the KB2040.

Assembly of this keyboard requires soldering skills and the instructions must be followed closely. You can find our assembly instructions in this dedicated guide. It's highly recommended to get the keyboard working with CircuitPython first before switching to QMK.

Don't feel like building the firmware yourself? You can give QMK a quick try by dragging the UF2 file below to the RPI-RP2 bootloader drive:

The build steps similar to for the other firmware we've followed in this guide. The keyboard is 40percentclub/gherkin and the keymap is default. This time, since the firmware was originally designed for the pro micro, we have to specify that QMK should "convert to" the KB2040 using the CONVERT_TO setting. Just add that to the command line when making the firmware:

cd ~/qmk_firmware
qmk flash -kb 40percentclub/gherkin -km default -e CONVERT_TO=kb2040

In either case, you should get a build log displayed in the terminal, and at the end a .uf2 file is created:

Ψ Compiling keymap with gmake --jobs=1 40percentclub/gherkin:default:flash

QMK Firmware 0.17.5
Making 40percentclub/gherkin with keymap default and target flash

arm-none-eabi-gcc (GNU Arm Embedded Toolchain 10-2020-q4-major) 10.2.1 20201103 (release)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO

Size before:
   text	   data	    bss	    dec	    hex	filename
      0	  32256	      0	  32256	   7e00	40percentclub_gherkin_default_kb2040.uf2

Compiling: keyboards/40percentclub/gherkin/gherkin.c                                                [OK]
Compiling: .build/obj_40percentclub_gherkin/src/default_keyboard.c                                  [OK]
[many lines deleted]
Linking: .build/40percentclub_gherkin_default_kb2040.elf                                            [OK]
Creating binary load file for flashing: .build/40percentclub_gherkin_default_kb2040.bin             [OK]
Creating load file for flashing: .build/40percentclub_gherkin_default_kb2040.hex                    [OK]
Creating UF2 file for deployment: .build/40percentclub_gherkin_default_kb2040.uf2                   [OK]
Copying 40percentclub_gherkin_default_kb2040.uf2 to qmk_firmware folder                             [OK]

Size after:
   text	   data	    bss	    dec	    hex	filename
      0	  32240	      0	  32240	   7df0	40percentclub_gherkin_default_kb2040.uf2

Flashing /media/jepler/RPI-RP2 (RPI-RP2)
Wrote 64512 bytes to /media/jepler/RPI-RP2/NEW.UF2

The Default Keymap

The first layer contains the standard alphabet, escape, backspace, space, and enter. To access further features, hold one or more keys on the bottom row.

For instance, to type an uppercase "Z", hold the "Enter" key (which functions as shift when held) and press the "Z" key.

The second image is "layer 1", so to type a "0" hold down "Space" and press "P". The symbols that go with shifted numbers also appear on "layer 2" without shift, so to type a ")", hold down "Space", "Enter", and press "P" (Layer1+Shift) OR hold down "Backspace" and press "P" (Layer2).

Use further layers to access punctuation, cursor movement keys, and operating system special keys.

The symbol ▽ indicates that this layer doesn't define the key, so the base layer's definition is used. So for example, holding C and pressing L types ";" but holding C and pressing S types "s".

For more on layers, see the dedicated page in QMK's documentation.

This guide was first published on Jul 26, 2022. It was last updated on Jul 26, 2022.

This page (Adafruit KB2040 on the PB Gherkin 30% Keyboard) was last updated on Jul 20, 2022.

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