# HHKB Professional Classic: vendor HID and firmware investigation

> HHKB-reverse-engineering investigates the vendor USB HID protocol of the HHKB Professional Classic keyboard. It documents 64-byte request and response frames, command behavior, keymap layouts and firmware-dump behavior, with macOS IOKit tools for probing and changing keymaps.

- Type: Case study
- Targets: Firmware · Protocol
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-06
- Added to the catalog: 2026-11-08
- Original resource: <https://github.com/m1sk9/HHKB-reverse-engineering>
- Primary source: <https://github.com/m1sk9/HHKB-reverse-engineering/blob/33db39081a8081f128024ee62cf1ba022c63f360/README.md>
- Catalog page: <https://awesomerea.org/resources/hhkb-professional-classic-case/>
- Record JSON: <https://awesomerea.org/resources/hhkb-professional-classic-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/hhkb-professional-classic-case/index.md)

## Requirements & limits

- **Prerequisites:** Building the tools requires the Xcode command line tools.
- **Scope:** The author reports measuring the findings on a PD-KB401B with firmware A4.29 under macOS 27.0.
- **Limits:** Firmware flashing is not implemented; the author reports that dumping firmware leaves the keyboard read-only until it is unplugged and replugged.
- **License:** MIT License.

## Primary sources

1. <https://github.com/m1sk9/HHKB-reverse-engineering/blob/33db39081a8081f128024ee62cf1ba022c63f360/README.md>
2. <https://github.com/m1sk9/HHKB-reverse-engineering/blob/33db39081a8081f128024ee62cf1ba022c63f360/docs/protocol.md>
3. <https://github.com/m1sk9/HHKB-reverse-engineering/blob/33db39081a8081f128024ee62cf1ba022c63f360/docs/firmware.md>

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## About this entry

The description was reviewed against primary sources.
Original editorial content: MIT. Linked projects, papers and assets retain their own rights and licenses.