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EdgeTX RC Input Logger for RadioMaster MT12

1. Architecture

Overview

The logger is split into two layers:

  1. Logging core (RCLOG/RCLOGC.lua)

    • Auto-discovers all available sources at startup.
    • Controls sample rate via getTime().
    • Buffers samples in RAM and flushes to the SD card in batches.
    • Manages recording state and file lifecycle.
    • Writes a stable CSV format for the desktop app.

  2. EdgeTX wrappers

    • TELEMETRY/RCLOG.lua — recommended for real sessions; runs in the background via background() while the model is active.
    • TOOLS/RCLOG.lua — useful for manual tests launched from SYSTEM > TOOLS without touching model configuration.

Both wrappers call the same core. The core is configured via an options table passed to newLoggerApp().

Source discovery

At init() the script auto-discovers all available sources by calling getFieldInfo(name) for each candidate and storing the returned id. Sources that don't exist on the radio are silently skipped.

Discovery order and candidates:

Group Names tried
Raw inputs (pre-mixer) input1 … input16
Output channels (post-mixer) ch1 … ch16
Switches sa sb sc sd se sf sg sh
System tx-voltage timer1 timer2 rssi
Telemetry sensors RxBt Curr Cels Tmp1 Tmp2 RPM

At runtime, values are read with getValue(fieldId) — a single call per source per tick using the pre-resolved field ID. getFieldInfo() is never called inside the sample loop.

Internal flow

init()
  → detect EdgeTX version
  → auto-discover sources (getFieldInfo per candidate)
  → refreshValues() once

background() / run()  [called every EdgeTX tick]
  → refreshValues()   [getValue(fieldId) for each source]
  → sample(nowTick)   [write csvRow to buffer if interval elapsed]
  → shouldFlush()     [flush buffer to SD if threshold reached]

destroy()
  → flushBuffer()     [final write, close file]

2. SD card folder structure

SDCARD/
├── LOGS/
│   ├── 20260512_214501_TT02.csv
│   └── 20260512_220812_TEKNO.csv
└── SCRIPTS/
    ├── RCLOG/
    │   └── RCLOGC.lua        ← shared core
    ├── TELEMETRY/
    │   └── RCLOG.lua         ← telemetry wrapper
    └── TOOLS/
        └── RCLOG.lua         ← tool wrapper

Notes:

  • LOGS/ already exists on a normal EdgeTX SD card; the script does not create directories.
  • Log filenames follow the pattern YYYYMMDD_HHMMSS_MODELNAME.csv. If no RTC is available, a tick-based fallback is used: t<tick>_MODELNAME.csv.
  • RCLOGC.lua is the shared core — never called directly by EdgeTX.

3. Generated CSV

Values are written raw — exactly as returned by getValue(fieldId). No normalization or calibration is applied.

Typical raw value ranges:

Source type Range
Analog (inputs, channels) −1024 … 1024
Switch −1024, 0, or 1024 (3-pos) / −1024 or 1024 (2-pos)
Telemetry (RxBt, Curr, etc.) Sensor-dependent units

Example output with the default 4-channel layout:

timestamp,input1,input2,ch1,ch2,ch3,ch4,sa,sb,tx-voltage
100,-512,0,-530,10,512,0,-1024,1024,124
104,-490,12,-510,14,512,0,-1024,1024,124
108,-470,24,-492,18,512,0,-1024,1024,124

Conventions

  • timestamp — getTime() ticks, 10 ms each. The desktop app converts to time_ms by subtracting the first tick.
  • Column names are exactly the source names discovered at init() — whatever getFieldInfo() returned for that radio.
  • Only sources that existed on the radio at startup appear as columns.
  • Values of 0 are written if getValue() returns nil for a source.

Sample rate

Fixed at 25 Hz (sampleIntervalTicks = 4 ticks of 10 ms). EdgeTX does not guarantee exact callback timing, so sample timing is based on getTime() — never on counting callbacks.

Flush policy

Samples are accumulated in a RAM buffer and written to the SD card in batches:

  • After 25 samples (1 second at 25 Hz), or
  • After 100 ticks (1 second) have elapsed since the last flush — whichever comes first.

The file is opened in append mode, written, and closed immediately after each flush. This minimises the open-file window and limits data loss to at most 1 second of samples if power is cut.

4. User interface (LCD)

The LCD layout on the MT12 monochrome display:

RCLOG TEL                    25Hz
────────────────────────────────
ST  [████████░░░░░░░░░░░░░]  +42%
THR [░░░░░░░░░░█████░░░░░░]  +28%
────────────────────────────────
REC  00:12.4              3108
/LOGS/20260517_180258_TT02.csv
                          ENTER
  • ST bar — live display of input2 (steering), normalized for display only.
  • THR bar — live display of input1 (throttle), normalized for display only.
  • ENTER — toggles recording on/off.
  • While recording: shows elapsed time and total sample count.
  • While stopped: shows number of discovered sources and ENTER hint.
  • Errors and warnings appear in the footer line.

Note: the display normalization (normalizeRaw) divides by 1024 and clamps to −100..100. This is only for the bars on screen — it does not affect the CSV values.

5. Recording control

ENTER toggles between stopped and recording:

  • Stopped → Recording: opens (or creates) the session file, writes the CSV header if the file is new, starts sampling.
  • Recording → Stopped: flushes the buffer and closes the session.
  • In Tool mode, EXIT or RTN calls destroy() and exits the script.

There is no menu, no calibration wizard, and no pre-recording setup. The script starts immediately on ENTER.

6. Performance notes

What the design does

  • Resolves all getFieldInfo() calls once at init() — never inside the sample loop.
  • Uses getValue(fieldId) (by numeric ID) rather than getValue("ch1") (by name) — avoids string lookups on every tick.
  • Buffers samples in a Lua table; writes to SD only on flush, not on every sample.
  • Opens and closes the file on each flush — no persistent file handle.

What to avoid when extending

  • Calling getFieldInfo() inside background() or run().
  • Keeping a file handle open between flushes.
  • Complex string.format() calls or large concatenations inside sample().
  • Targeting sample rates above 25 Hz in Lua on monochrome radios — the scheduler cannot reliably sustain them.

7. Video synchronisation

Practical approach

  1. Primary: use the timestamp field (10 ms ticks) as the session clock.
  2. Sync mark: create a visible or audible event when recording starts (switch flip, beep) — align this point in the video editor.
  3. Fine offset: use offset_ms in MT12OverlayStudio to correct camera latency or capture-card delay.

Recommended workflow

  1. Record the session video.
  2. Press ENTER on the radio to start logging; create a sync mark.
  3. Transfer the CSV from the SD card.
  4. Load the CSV in MT12OverlayStudio.
  5. Adjust offset_ms once per session until the overlay aligns.

8. Official sources