# FieldReg – Modbus Decoder — Decode PLC registers offline

> Decode PLC registers offline (iPhone/iPad app by Aphelion Engineering Pty Ltd.)

- Source: https://appshunter.io/ios/app/fieldreg-modbus-decoder/id6782255844 (this page in markdown: same URL + `.md`)
- Developer: [Aphelion Engineering Pty Ltd](https://appshunter.io/developer/1896778280)
- Category: Utilities
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 26.0 · 1 MB
- Languages: American English
- Released: 2026-06-24
- Data updated: 2026-06-29
- User reviews in markdown: https://appshunter.io/ios/app/fieldreg-modbus-decoder/id6782255844/reviews.md

## What is FieldReg?

The register decoder that lives in your pocket — and never phones home.

You're at a panel with a flow meter publishing FLOAT32 and a SCADA tag that reads garbage. FieldReg decodes 1, 2, or 4 Modbus registers into every interpretation simultaneously — signed and unsigned integers, FLOAT32/64 — in all four byte orders (ABCD, CDAB, BADC, DCBA), with a plausibility flag that points at the value that makes physical sense.

Decode — hex or decimal entry, smart paste, swap word order in one tap, automatic history.
Address — protocol address ↔ 1-based ↔ 40001 ↔ 400001, with read/write function codes per entity.
Scale — linear scaling, 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.
Bits & CRC — tappable 16-bit grid, hex/decimal/binary/octal live, CRC-16/MODBUS with the on-wire byte order spelled out.
Reference — eight offline field sheets: function codes, exception codes, RTU/TCP framing, RS-485 wiring, serial gotchas, data types, PLC addressing, 4–20 mA.

100 % offline. No account. 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: 16-bit decode, FLOAT32 in all four orders, and the address converter. One affordable one-time purchase unlocks the rest — no subscription.

Made by a controls engineer, for the people standing in front of the panel.

—
Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Privacy Policy: https://aphelionengineering.com.au/fieldreg/privacy/

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| FieldReg Pro | $12.99 | one-time |



## Version history (last 1 release)

### 1.0.0 — 2026-06-24

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-29.*