# X-40 laser rangefinder: circuit and firmware reconstruction

> The X-40 laser rangefinder study reconstructs the tape measure's circuit and replaces its firmware for DIY distance measurement. The author captured I2C packets with a logic analyzer, decoded modulation-frequency values and wrote firmware that processes signals with a Goertzel algorithm; PC utilities display captured data and results.

- Type: Case study
- Targets: Firmware · Protocol
- Category: Independent reconstruction cases
- Relationship: Independent reconstruction project
- Sources reviewed: 2026-11-08
- Added to the catalog: 2026-11-09
- Original resource: <https://github.com/iliasam/Laser_tape_reverse_engineering>
- Primary source: <https://github.com/iliasam/Laser_tape_reverse_engineering/blob/fd829618ed7075ca104cbe742e6d5be4f7f31813/README.md>
- Catalog page: <https://awesomerea.org/resources/x40-laser-rangefinder-case/>
- Record JSON: <https://awesomerea.org/resources/x40-laser-rangefinder-case/record.json>
- Chinese version: [简体中文](https://awesomerea.org/zh/resources/x40-laser-rangefinder-case/index.md)

## Requirements & limits

- **Prerequisites:** Requires a supported X-40 module; the README lists 512A, 701A, U85A/U85B and B2A families, while M88B is unsupported.
- **Prerequisites:** The fast distance firmware requires zero-distance calibration on first start.
- **Testing evidence:** The author reports accuracy varying from 1 to 10 mm with distance and surface type.
- **License:** MIT License.

## Primary sources

1. <https://github.com/iliasam/Laser_tape_reverse_engineering/blob/fd829618ed7075ca104cbe742e6d5be4f7f31813/README.md>
2. <https://github.com/iliasam/Laser_tape_reverse_engineering/blob/fd829618ed7075ca104cbe742e6d5be4f7f31813/PC_utility/Readme.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.