On March 30, 2024, @foostan, the designer of Corne V4, announced that he has updated the official X and updated its firmware guide.
Click here for Corne V4 Firmware Guide ▷▷▷.
V4 supports not only “VIA /Remap” as before, but also “Vial”.
In addition to the regular 3×6 layout, firmware for the so-called “QAZ” 3×5 layout is also available.
Due to a change in the microcontroller used in V4, firmware can be written by drag-and-drop without using software such as QMK Toolbox.
Connect to PC while holding down the BOOT button, or press the reset button while holding down the BOOT button while connected to PC. The RPI-PR2 device will then be mounted.
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Drop the downloaded uf2 file into the RPI-PR2 device to complete writing.
https://github.com/foostan/crkbd/blob/main/docs/firmware/rev4/firmware_jp.md
One thing to note is that if you use VIA-compatible firmware, you will need to load the .json file.
This is probably because the .json has not yet been merged into VIA.
Based on my experience with other keyboards, it seems to take some time for a request to be approved.
Enable the “Show Design tab” on the settings screen Then, a loading screen (Paintbrush icon) will be added, and you can change the keymap by dragging and dropping the downloaded .json file there.
On the other hand, as for Vial, there is no need to read json files like VIA, because the mechanism “does not require registration of json files”.
Probably, for products purchased at Yousha Kobo, the firmware has already been written in, so the baking process, etc. described here will not be necessary.
Personally, I prefer to use Vial, which is easy to play with various parameters.