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Field notes, debugging
logs, opinions.

Long-form technical writing on industrial protocols. Mostly Modbus this year. Mostly worked examples. Mostly free of marketing.

4 posts · updated weekly
01· Illegal Function02· Illegal Data Address03· Illegal Data Value04· Slave Device Failure05· Acknowledge06· Slave Device Busy08· Memory Parity Error0A· Gateway Path Unavailable0B· Gateway Target Failed
Featured26 May 2026·10 min

Modbus function codes: reads, writes, and why some are read-only.

The major Modbus function codes (01-06, 15, 16) - what each one targets, real examples of the data they carry, and why the protocol splits read-only and read-write into separate tables.

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24 May 2026
Debugging

Modbus byte order explained: ABCD, CDAB, BADC, DCBA decoded.

How 32-bit floats and integers sit across two Modbus registers. Every byte-order variant (ABCD, CDAB, BADC, DCBA) explained, plus the field workflow to identify yours.

11 min →
12 May 2026
Debugging

Modbus exception codes explained: every code and how to fix it.

Every Modbus exception code (Modbus RTU and Modbus TCP), what each one really means in practice, and how to chase it down with a frame capture.

12 min →
10 Mar 2026
Voice

Why we're building Coilware (and why now).

A short, slightly bitter note about industrial software in 2026 and what we'd like it to be.

4 min →