SNUADC channels are read one after another¶
The SNUADC firmware reads its 8 channels in turn, about 0.1 ms each, so within one sample the last channel is read up to about 0.8 ms after the first. The channel order is not known.
| Status | likely: consistent, with a known gap. |
| Devices | SNUADC |
| Variables | ECG lead II (SNUADC), Arterial pressure (SNUADC), Plethysmogram (SNUADC) |
What it means¶
A fixed sub-millisecond skew between SNUADC channels: a floor on same-clock alignment such as ECG to arterial pressure. A monitor line seen in both ART and PLETH puts ART about 0.3–0.4 ms ahead.
Evidence¶
| Study | Date | Status | Summary |
|---|---|---|---|
| Monitor clocks in the waveforms' spectral lines | 2026-10-17 | open | Differences of the raw converter counts show lines from the monitor's analogue outputs: 240 Hz in arterial pressure and plethysmogram, and a 30 Hz family in the plethysmogram alone. Each measures a monitor clock against SNUADC. |
| The SNUADC firmware | 2026-10-13 | current | The public SNUADC firmware explains the board's timing: it sends no time stamps, samples on its 16 MHz crystal, loses time rather than bunching samples after a stall, reads its channels one after another, and truncates its values. A predicted fault at the microsecond counter's wrap was not found in the data. |