About
FirmGod is a small set of calculators for the parts of embedded and industrial protocol work that are easy to get wrong and tedious to check by hand: Modbus frame construction, CRC parameters, and the byte order conventions that decide whether a 32-bit register pair reads as a temperature or as noise.
How results are verified
Correctness matters more than features here, because a calculator that is quietly wrong is worse than no calculator at all. Two things guard against that:
- Catalog check values. Every CRC model is tested against the published CRC of the string
123456789. That single value exercises the polynomial, initial value, both reflection settings, and the final XOR simultaneously. - Specification examples. The Modbus frame builder is tested against worked examples from the protocol specification, including the exact byte sequences those documents publish.
These checks run as an automated test suite, so a change that breaks one of them cannot ship.
Privacy
Every tool runs entirely in your browser. Frames, register values, and messages you paste are never uploaded. The privacy page covers the site's cookies and advertising in detail.
Reporting a problem
If a result disagrees with your hardware, that is worth hearing about — the interesting cases are usually a vendor doing something the specification does not describe, which is exactly the kind of thing these tools should handle. Send the input, the value you expected, and the device if you can name it, to contact@firmgod.com.
A note on accuracy
These calculators are provided as-is and without warranty. Verify anything safety-relevant against your device documentation and your own measurements before relying on it in production.