It doesn't matter which experiment generator you use to run your computer-based psychology experiments the Black Box ToolKit USB TTL Module helps with basic TTL event marking/TTL triggering when you don't have access to a parallel port.

USB TTL event marking module key features

Designed as a parallel port replacement for simple event marking. Plug in to a USB port on your PC and our USB TTL Module will appear as a Virtual Com Port (VCP). To event mark send two hex bytes from your experiment generator. Quickly and easily TTL event mark/TTL trigger with any experiment generator via standard one line serial commands, e.g. task events in E-Prime. Works out of the box with E-Prime, SuperLab, Presentation, Inquisit, PsychoPy or any other software that can read and write to a standard serial port.

When triggering from MRI, EEG, ERP, MEG systems wait for a sync pulse that has been converted to two incoming hex bytes. Think of the module as a USB to TTL adapter or TTL to USB interface.

All USB TTL modules ship with a USB host lead. An optional breakout board enables you to wire your own cables before making them permanent.

*Remember although our USB TTL Modules are millisecond accurate they can't automatically correct for any mistimings that are inherent within the experiment generator you use. Hardware capable of sub-millisecond accuracy. Timing accuracy tied to PC and experiment generator used.

If you wish to check the accuracy and consistency of your experiment generator, or system as a whole, you are advised to use a Black Box ToolKit v2 together with a BBTK USB response pad. For independent TTL event marking/TTL triggers you should combine a response pad with our mBBTK v2 which is designed for monitoring stimuli and event marking.

Key features

  • 16 Digital +5 V TTL Lines
    • 8 TTL Input
    • 8 TTL Output
  • TTL Input Lines configured as an 8 bit port
  • TTL Output Lines configured as an 8 bit port
  • Change detection on TTL Input lines
  • TTL Input to 2 hex bytes conversion representing 255 possible states
  • Event marking: 2 hex bytes to TTL Output across 8 bit port representing 255 possible states
  • TTL Output lines automatically latch once set
  • Works out of the box with PCs/Macs/Linux – fully plug in & play
  • Appears as a Virtual Com Port (VCP)
  • Compatible with all Psychology experiment generators, e.g. E-Prime, SuperLab, Presentation, Inquisit, DMDX, ERTS, DirectRT, PsyScope, PsychoPy, OpenSesame etc.
  • Works with any software that can access a standard serial port
  • Comes complete with our own timing validation software which checks round trip timing on your PC
  • Fully documented API complete with examples
  • Small and unobtrusive – Dimensions: 67.1mm x 28.2mm x 67.1mm (WHD)
  • LED indicators for Input (green) and Output (red)
  • Full-speed USB 2.0 (compatible with USB 3.0)
  • Scans for TTL I/O changes 109,000 times each second
  • Millisecond accurate TTL event marking*

Example usage

Using the BBTK USB TLL event marking module is easy. Simply open a standard serial port and send two hex bytes to event mark. In the examples shown below for PsychoPy, E-Prime and MATLAB the module event marks on TTL Out Line 1 (01) immediately prior to a stimulus image being displayed. Once the stimulus terminates all TTL lines are cleared with 00.




import serial
ser = serial.Serial(0, 115200, timeout=1)
<My Stimulus Image Shown Here>
Serial.WriteString "01"
<My Stimulus Image Shown Here>
Serial.WriteString "00"
s = serial('COM1');
set(s, 'BaudRate', 115200, 'DataBits', 8, 'StopBits', 1, 'Parity', 'none');
fprintf(s, '01');
<My Stimulus Image Shown Here>
fprintf(s, '00');

Breakout board

A breakout board lets you quickly and easily connect individual TTL lines before making a permanent connection.


Pins 2~9 correspond to TTL Output Lines 1~8 and pins 10~17 to TTL Input Lines 1~8. Pins 18~25 are grounds. Output pins shown in RED, input pins in GREEN.

Configuration and latency testing

Configuration software lets you check that the module is operating correctly and assess round trip timing on your PC.

Technical specifications

  • ABS plastic enclosure – Dimensions: 67.1mm x 28.2mm x 67.1mm (WHD)
  • Full-speed USB 2.0 (compatible with USB 3.0)
  • 1x 25-way male D connector for connecting your equipment to 8x TTL Output/TTL trigger lines and 8x TTL Input lines from your equipment. Plus 8x GND pins
  • Appears to the host PC/Mac/Linux system as a standard serial port (VCP – Virtual Com Port)
  • Connects to the host PC via standard USB type A to B lead
  • Fully updatable firmware - 32K flash RAM (100,000 Erase/Write Cycles)
  • Supplied with configuration and latency validation software for Windows XP, Vista, Win 7, Win 8/8.1 and Win 10
  • Built-in hardware timing checks based on elapsed time between two sequential event marks
  • Checks for a TTL event mark or trigger event 109,000 times a second (109kHz sampling rate)
  • Typical time to send a TTL output or event mark from a two byte hex code from the PC, 254µs#
  • Typical time to respond to a TTL input/trigger pulse or sync signal and send a two byte hex code to the PC, 350µs#
  • Typical time for 50 TTL outputs or event marking pairs (on|off), M = 290µs, SD = 10µs, measured using our configuration and latency validation software for Microsoft Windows (Win 7 64 SP1, USB 2) and modules internal hardware timer#

#Dependent on specific USB subsystem and using the USB TTL Configuration utility to check correct for correct installation.

*Remember although our USB TTL event marking modules are millisecond accurate they can't automatically correct for any mistimings that are inherent within the experiment generator you use.

Unless otherwise labelled, all products offered for sale by The Black Box ToolKit Ltd are for academic study and/or research use only.

About company

The Black Box Toolkit Ltd was founded in 2003 by a team of psychologists, software experts and electronic engineers.

Dedicated to improving the millisecond timing accuracy and experimental rigor of researchers in the behavioral and brain sciences.

We provide hardware, software and consultancy solutions across a wide range of fields to make this a reality. Print flyer

Get in Touch

  • Phone:
    +44 (0)114 3030056
  • Email:
  • Address:
    The Black Box ToolKit Ltd,
    PO Box 3802, Sheffield,
    S25 9AG, UK