# TC66 custom firmware: a replacement image for the RuiDeng USB-C meter

> Replacement firmware for the RuiDeng TC66 and TC66C USB-C meters. Stock firmware is not in the repository; make release in rust/ writes tc66fw-release.enc.bin, an AES-encrypted image for the stock bootloader.

- Type: Case study
- Targets: Firmware
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-03
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/FletcherD/tc66-custom-fw>
- Primary source: <https://github.com/FletcherD/tc66-custom-fw/blob/65accb42ce94526649f7553c927d4edae9389a71/README.md>
- Catalog page: <https://awesomerea.org/resources/tc66-meter-firmware-case/>
- Record JSON: <https://awesomerea.org/resources/tc66-meter-firmware-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/tc66-meter-firmware-case/index.md)

## Requirements & limits

- **Prerequisites:** Commit 65accb42ce94526649f7553c927d4edae9389a71. The README says the TC66C, with a GD32F150G8 MCU, has been tested, and that the TC66 uses the same board design and has not been tested. Other RuiDeng meters are not supported. The stock image is not redistributed. uv run tc66flash.py stock downloads official V1.18 and checks SHA-256 ef796b29557c91e0a469740ba1934ca0a838916c76ab55eb6d1253da32830940. tools/tc66flash.py maps USB IDs 0x28E9:0x018A.
- **Testing evidence:** From rust/, make release writes tc66fw-release.enc.bin. The Makefile calls that file an AES-encrypted image for the stock bootloader. The README says the bootloader itself is never written.
- **License:** LICENSE is the MIT license, copyright 2026 Fletcher.

## Primary sources

1. <https://github.com/FletcherD/tc66-custom-fw/blob/65accb42ce94526649f7553c927d4edae9389a71/README.md>
2. <https://github.com/FletcherD/tc66-custom-fw/blob/65accb42ce94526649f7553c927d4edae9389a71/rust/Makefile>
3. <https://github.com/FletcherD/tc66-custom-fw/blob/65accb42ce94526649f7553c927d4edae9389a71/tools/tc66flash.py>
4. <https://github.com/FletcherD/tc66-custom-fw/blob/65accb42ce94526649f7553c927d4edae9389a71/LICENSE>

## More in Firmware and hardware

- [UV-K5: an open reimplementation of Quan Sheng firmware v2.1.27](https://awesomerea.org/resources/uv-k5-firmware-case/index.md) · Case study
- [R64Emu: low-level Nintendo 64 hardware reconstruction](https://awesomerea.org/resources/r64emu-n64-case/index.md) · Case study
- [Nuked-MD-FPGA: Sega Mega Drive chipset reconstruction](https://awesomerea.org/resources/nuked-md-fpga-case/index.md) · Case study
- [CamLink 4K: replacement gateware and firmware for an Elgato capture card](https://awesomerea.org/resources/camlink-4k-case/index.md) · Case study
- [pw_firm: a Pokéwalker firmware decompilation](https://awesomerea.org/resources/pw-firm-pokewalker-decomp-case/index.md) · Case study
- [Strato: Nintendo Switch system emulation on Android](https://awesomerea.org/resources/strato-switch-emulation-case/index.md) · Case study

## 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.