A companion app for the EEVblog 121GW multimeter, for iPhone, iPad, Mac, Android, Windows and Linux. Built with .NET 10 and .NET MAUI.
Website · Support · Privacy · The 121GW
- Live LCD. A drawing of the meter's display: main and sub readings, units, the bar graph and every symbol.
- Remote buttons. Press any of the meter's eight buttons from the app, short or long.
- Logging. Every reading is logged while connected, with a live trend graph and min/max/average/peak-to-peak. Logging keeps running with the screen locked (iOS), and the recording is kept on disk, so closing the app doesn't lose it.
- Readable graphs. The meter screen shows the last 10 minutes; full screen shows the whole recording, with long recordings drawn as an average line over a min/max band. Pinch to zoom, drag to pan.
- Saved sessions. Save a recording with a name and notes; each keeps its graph and statistics.
- CSV export. Timestamped readings in SI units, ready for a spreadsheet.
- Continuity beep. In continuity and resistance modes the phone beeps and vibrates below a threshold you set, with hysteresis so it doesn't chatter.
- Signal and battery. The connection line shows the meter's signal strength and battery.
- Reconnects by itself to the last meter when it comes back in range (can be turned off in Settings).
- Demo meter. Try the app without a meter (simulated readings).
- Works with Claude (Mac, Windows and Linux). An optional, local-only MCP server lets an AI assistant read the meter, look at recent readings, press buttons and save sessions. See docs/MCP.md.
Readout is an independent, open-source project. It is not made, endorsed or supported by EEVblog. 121GW and EEVblog are trademarks of their owners.
| Platform | Status |
|---|---|
| iOS / iPadOS 15+ | ✅ |
| macOS (Mac Catalyst) 12+ | ✅ |
| Android 6+ | ✅ |
| Windows 10/11 | ✅ builds on Windows |
| Linux (GTK 4.12+, BlueZ) | Preview: MAUI's GTK4 backend, see Linux |
You need the .NET 10 SDK and the MAUI workload (dotnet workload install maui), plus Xcode
for Apple targets and the Android SDK for Android.
dotnet test --project Readout.Testsdotnet build Readout -f net10.0-maccatalystNo meter? Every build has Try the demo meter on the connect screen.
The wiki has the rest:
- Building: every platform, code coverage, running on a device.
- Publishing: store packages, Linux tarballs, releasing from a tag.
- Linux: running it, what's different there, testing in Docker.
- Repository layout: what each project holds.
In this repository: the 121GW protocol, the MCP server, FS9721 meters through an ESP32 bridge and releases from CI.
The meter protocol comes from the official EEVblog 121GW app by David Ledger (MIT). See THIRD_PARTY_NOTICES.md.
MIT. Privacy: PRIVACY.md (no data collected).