How to use Codex to build a USB macropad
Codex wrote firmware for a homemade ESP32-S3 USB macropad. Its maker wired keys, printed the enclosure and published code, CAD and shortcut setup documentation.
reddit.com
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Write ESP32-S3 USB-keyboard firmware for my hand-wired macropad using this GPIO map and configured app shortcuts. Include the rotary control, keys and lighting, then give me a physical input check for every binding. Keep enclosure dimensions and soldering decisions for my review.
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See placements →What happened
A functioning unofficial USB macropad was documented with firmware, printable files and a parts list. Wiring and enclosure design were human work; no measured productivity gain is claimed.
Reported by NishkalKashyap — RedditHow the agent did it
- Kashyap bound application shortcuts and selected an ESP32-S3 keyboard interface.
- Codex generated the firmware while the author hand-wired the keys.
- The author modeled and printed the enclosure and published firmware, CAD and a parts list.
Where a person stepped in
Kashyap hand-wired the keys, modeled the enclosure in Fusion 360 and bound keyboard shortcuts in the Codex app.
NishkalKashyap built a hobby USB controller inspired by Codex Micro and used Codex to write its ESP32-S3 firmware. The device operated as a standard USB keyboard, sending shortcuts the author had bound inside the Codex application.
The hardware had a dedicated GPIO for each key, a rotary control and RGB lighting. Its shortcuts covered approving or rejecting requests, sending input, changing tasks, selecting reasoning level and push-to-talk. Using ordinary keyboard input kept the controller tied to configured shortcuts rather than requiring a new application integration.
The physical build remained the author's work. Kashyap hand-wired the keys and modeled a printed enclosure in Fusion 360. The public repository supplied PlatformIO firmware, CAD and printable files, a parts list, process photographs and a demonstration, making the artifact more concrete than the announcement alone.
The author describes it as a fun weekend return to embedded development, and explicitly calls it an unofficial hobby project. Codex's evidenced contribution is the firmware, not the enclosure design or soldering. The source also does not demonstrate that a dedicated keypad improved work speed; its result is a functioning, documented physical interface whose usefulness depends on the owner's shortcut setup.
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Source: Reddit · NishkalKashyap
Frequently asked questions
How did the device control Codex?
It appeared as a USB keyboard and sent configured application shortcuts.
Which parts were human-made?
Hand wiring and the Fusion 360 enclosure model.
Is it an official accessory?
No. The author identifies it as an unofficial hobby project.
More details
About this account
Kashyap bound application shortcuts and selected an ESP32-S3 keyboard interface. Codex generated the firmware while the author hand-wired the keys.
Original author post and repository README opened. Firmware is explicitly attributed to Codex; wiring and CAD are human. Hobby controller is not affiliated with OpenAI and no productivity gain is established. Suggested prompt written by Agents In Use; no original task prompt was published in the verified account.
Credit: NishkalKashyap — Reddit
Source published 28 Jul 2026
Source checked 14 Oct 2026
Tools and topics
Codex · ESP32-S3 · PlatformIO · Fusion 360 · 3D printer
USB controller · Hobby firmware
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.