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Signal-quality checks

YAMS → 📡 Signal Quality pulls a raw ECG/PPG snapshot from every connected wristband so you can see electrode / optical contact before you trust a recording. Initialize the MSense device on the Session Dashboard first, then open this tab.

The Signal Quality tab, idle

Snapshot vs live stream

  • 📡 Snapshot all wristbands — a fixed-length capture (128 KiB per wristband: ~21 s of ECG or ~8 s of PPG of pre-buffered history, then a forward window it acquires live). Saved to disk — the session folder if a recording is running, otherwise <home>/data/sqc_snapshots/.
  • ▶️ Start live stream (all) — a continuous stream into a rolling in-memory plot, for a longer contact check. Not saved to disk or the .xdf.
  • ✖ Cancel all / ⏹️ Stop live stream (all) — stop whatever is running.

Capture mode

Mode Stops when… Use for
All the full 128 KiB is through a complete reference snapshot
History Only the pre-buffered history window is through a fast check — no waiting for live acquisition
Custom N seconds of forward data have arrived "give me 5 s of live signal and stop"

Custom — stop after N s is only editable when Capture mode is Custom.

Streaming mode

How the wristbands share the single BLE radio:

Mode Behaviour
Sequential one wristband finishes completely before the next starts — safest, slowest
Parallel all at once — fastest wall-clock, more likely to stall
Hybrid pipelined — the next wristband starts once the previous drops out of its heavy history burst

Reading the status line

Each wristband shows a live line while a snapshot runs:

You see Meaning
📡 receiving (forward) 95.2 KiB/128.0 KiB (74%) + transfer stats healthy, in progress
💾 finalizing… decoding and saving
✅ ECG/PPG … saved \`` done — the file is on disk
✂ partial Ns Custom / History Only cut it short on purpose
🚫 rejected: <reason> the wristband refused (e.g. BUSY, NOT_RECORDING)
❌ <reason> / ❌ stalled … the transfer failed — see Abnormal handling

A snapshot in progress

Plot options

  • PPG channels show — Raw / Filtered / Both.
  • Filtered Y-axis min / max — fix the scale so successive snapshots compare.
  • Show history/forward boundary — a dashed line where the pre-buffered history gives way to live-acquired data.

Headless

A snapshot can be triggered and its outcome read from the API — see Headless control & API.

Next: MSense tools (YAMS).