What type of external triggers are supported?#

DSI devices record triggers as unsigned integers on a dedicated trigger channel. The bit depth varies by device:

Device	Trigger Bits	Value Range
DSI-24	8-bit	0–255
DSI-EEG+fNIRS	8-bit	0–255
DSI-VR300	4-bit	0–15
DSI-7	4-bit	0–15
DSI-Flex	4-bit	0–15

The 8-bit devices are the only ones that use all 8 trigger data lines. The 4-bit devices (DSI-VR300, DSI-7, DSI-Flex) use data lines D1–D4 only.

Trigger values appear in DSI-Streamer as decimal numbers and are represented visually by diamonds in the lower-left corner of the screen (D1 through D8, left to right).

Hardware Triggers (MMBT-S)#

The MMBT-S is the recommended device for sending hardware triggers directly from a stimulus computer. It connects via USB, presents as a serial port, and converts writes to the serial port into TTL pulses recorded on the DSI trigger channel. Your stimulus software (PsychoPy, MATLAB, Unity, custom scripts) writes a trigger value at the moment of stimulus onset.

Trigger Hub#

The Trigger Hub consolidates up to 8 independent trigger sources into a single output connected to the DSI headset — via wired cable or wireless receiver. It is used when you need more than one trigger source or require inputs that the MMBT-S alone does not support.

Input types:

Input	Connector	Use Case
Analog (Ch-3, Ch-6)	BNC	Function generators, TTL/CMOS logic, any 0–20V signal
Analog (Ch-7, Ch-8)	3.5mm stereo	Two-channel analog input
Audio (Ch-4)	3.5mm stereo	Line-level audio — triggers on audio envelope; < 0.5ms latency
Switch / Photodetector (Ch-1, Ch-5)	3.5mm stereo	Push-button events or screen flash detection via photodetector
Parallel Port	DB-25	Up to 255 trigger values from a PC’s parallel port

All analog and parallel port inputs accept 0–20V; the threshold is adjustable from 0.63V to 5.8V via a front-panel selector. Trigger outputs are 0–5V, matching DSI headset input requirements.

Latency:

Connection	Latency
Digital / analog / switch inputs	< 100 µs
Audio input	< 0.5 ms
Wireless transmission	12 ms ± 10 µs (compensated automatically in DSI-Streamer)

Other features:

Wired or wireless: connects to the headset via a trigger cable (parallel port output) or a wireless receiver that plugs directly into the headset’s trigger port. Wireless range is up to 9m; up to 18m with the included repeater.
AutoTrigger: generates a 1 Hz square wave on all outputs for clock-drift alignment across multiple acquisition systems (e.g., EEG + eye tracking).
Multi-device: a single Trigger Hub can be paired to multiple wireless receivers, enabling synchronized trigger delivery across multiple headsets (hyperscanning).

Minimum pulse specs: 20ms pulse width; 40ms minimum interval between triggers.

Software Triggers (LSL)#

Software triggering is supported via Lab Streaming Layer (LSL). LSL markers are time-synchronized with the EEG stream at the recording level, making them suitable for most stimulus presentation workflows.

For full details on trigger methods, timing, and setup

See the Learning: Triggers & Event Alignment page for a complete guide covering hardware triggers, software (LSL) triggers, serial port triggering for game engines, how to measure timing offsets, and recommended reading order.