Case study

Fosi Audio MD3: mapping the DAC and replacing its controller firmware

fosi-md3 investigates the Fosi Audio MD3 USB DAC and implements replacement firmware for its ESP32-S3 controller. Its notes map the USB mux, DAC I2C control, Savitech link and stock settings record from hardware observation and firmware disassembly; the ESP-IDF implementation preserves audio control and photo storage. The author reports testing on one unit.

Targets: Firmware · Protocol
Category: Independent reconstruction cases
Relationship: Independent reconstruction project
Sources reviewed: 2026-11-06
Evidence class: C2 code & docs, no demo or download

Stars: 0
Last commit: 2026-11-01
Language: C
License (GitHub): MIT

GitHub data as of 2026-11-10

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Evidence

Observed: Code, documentation and a demo observed; no download method found.
Checked: 2026-11-08

How evidence classes are assigned

Requirements & limits

Prerequisites: A Fosi Audio MD3 unit and a backup of its own 32 MB flash for restoration.
Prerequisites: ESP-IDF 5.5.1 and LVGL 9.2 for the replacement firmware; documented use was on macOS.
Limits: The author reports testing on one unit; power transitions remain unverified.
License: MIT license for the repository's original code and documentation.

Cite

BibTeX

@misc{fosi-md3-case,
  title = {{Fosi Audio MD3: mapping the DAC and replacing its controller firmware}},
  howpublished = {\url{https://github.com/BenevolentFutures/fosi-md3}},
  url = {https://github.com/BenevolentFutures/fosi-md3},
  urldate = {2026-11-06},
  note = {Awesome REA entry: \url{https://awesomerea.org/resources/fosi-md3-case/}}
}

Plain text

Fosi Audio MD3: mapping the DAC and replacing its controller firmware. https://github.com/BenevolentFutures/fosi-md3 (accessed 2026-11-06). Awesome REA entry: https://awesomerea.org/resources/fosi-md3-case/

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Primary sources

README.md GitHub · BenevolentFutures/fosi-md3 · Revision c34b4bf
docs/hardware.md GitHub · BenevolentFutures/fosi-md3 · Revision c34b4bf