Best way to route the SYNC_OUT pulse into an external recording PC / acquisition system

[dblizinski]

I'm running Open-Motion alongside a separate acquisition system and want to capture the SYNC_OUT pulse to time-align the two recordings. What cabling/adapter routes have worked best — e.g. SMA→BNC→USB, SMA→Arduino/USB, or something else?

Quick orientation: SYNC_OUT is the left SMA port on the underside of the console. It emits a 40 Hz square wave that pulses on every camera trigger. See the [SYNC_OUT spec in the docs](https://github.com/OpenwaterHealth/openmotion-sdk/blob/main/docs/scan-sequencing.md) for the full signal definition.

(If you're instead trying to drive Open-Motion's capture from an external clock, that's SYNC_IN, which is not currently available — verify current status.)

Before selecting adapters, confirm the SYNC_OUT output level in the docs ([TTL level — confirm]) and match termination/impedance on the receiving side.

Common routes:

1. SMA → BNC into a DAQ or the TTL/trigger input of your acquisition hardware. Many EEG/fNIRS rigs and lab DAQs accept a BNC TTL trigger directly. Usually, the most robust, lowest-latency path.
2. SMA → BNC → a DAQ / trigger box with a Lab Streaming Layer (LSL) outlet. If you're aligning multiple streams in LSL, bringing the pulse in through a device that publishes to LSL keeps it in the same clock domain as your other streams.
3. SMA → microcontroller (Arduino/Teensy) on a digital input, timestamping and forwarding over USB serial. Flexible and cheap, but adds a software layer and some jitter — fine for event marking; validate against your timing tolerance.

If you get a route working, reply with your setup — it helps the next person.