FieldReg · Modbus decoder · iOS
FieldReg is an offline Modbus / PLC register toolkit for the iPhone in your pocket. Decode 1, 2, or 4 registers into every interpretation at the same time — signed and unsigned integers, FLOAT32/64, in all four byte orders — plus address conversion, 4–20 mA loop maths, a bit & CRC inspector, and eight offline field sheets. It never phones home.
Scroll · six screens, all working in airplane mode
Five tools, plus a promise
No connection, no account, no clutter — just the maths you reach for at the panel, every interpretation on screen at once.
1, 2, or 4 registers as signed/unsigned ints and FLOAT32/64 across ABCD, CDAB, BADC and DCBA — with a plausibility flag pointing at the value that makes physical sense. Hex or decimal entry, smart paste, one-tap word swap, automatic history.
Protocol 0-based ↔ 1-based data model ↔ 40001 ↔ 400001, with the read and write function codes for each entity. Enter any reference and the entity follows.
Linear scaling and a 4–20 mA loop calculator with NAMUR range flags. 0/25/50/75/100% injection tables you can export as CSV straight into the loop-check record. Save instrument presets.
A tappable 16-bit grid with hex, decimal, binary and octal live side by side, and CRC-16/MODBUS with the on-wire byte order spelled out.
Function codes, exception codes, RTU/TCP framing, RS-485 wiring, serial gotchas, data types & byte orders, PLC addressing, and the 4–20 mA quick sheet — all offline.
No accounts, no analytics, no tracking. Your register values never leave the device — the App Store privacy label reads “Data Not Collected” because nothing is.
Free forever, Pro once
The free tier is genuinely useful on its own. Pro is a single one-time purchase — not a subscription — and you can restore it on every device signed in to your Apple Account.
Free
A$0
FieldReg Pro
One‑time · price shown on the App Store
The support page covers restores, unlocks, and the common questions — or email us directly.