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.

Designed as a parallel port replacement for simple event marking.

USB TTL event marking module pricing.

USB TTL event marking module key features

Designed as a parallel port replacement for simple event marking. Plug into 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 hardware is millisecond accurate and helps you produce simple event marks in your experiments it cannot automatically correct for any mistimings that are inherent within the experiment generator or other hardware you use. In short it does not guarantee that your event marks or triggers are accurate as your experiment generator is responsible to all timings and all it provides is a simple USB-TTL interface between your computer and third party equipment.

For example, if your experiment generator presents an image and does not produce an event mark in a timely fashion, your OS intervenes, or an anti-virus check runs, your event marks will remain inaccurate regardless of the quality of the event marking device. What | Why | How

For self-validation you should independently check the accuracy and consistency of your experiment generators presentation and response event marking with a Black Box ToolKit v3 together with a BBTK USB TTL module.

To independently TTL event mark stimuli and responses with sub-millisecond accuracy you should use our mBBTK v2. The unique mBBTK v2 takes over all timing and event marking duties from any experiment generator so you can be 100% sure of your presentation, synchronization, response timings and event marks.

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*
  • Platforms supported:
    • Microsoft Windows XP SP3, Vista SP2 (32/64), Windows 7 SP1 (32/64), Windows 8 (32/64), Windows 10 (32/64), Windows 11 (64 bit)
    • macOS / iOS#
    • Linux#
    • Android#
#BBTK Microsoft Windows software Apps not supported directly. Full API provided for control over serial regardless of platform used.

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.

Replacement USB host lead (A to B)

Used for connecting the base kit to the Host PC.

USB-C host lead (C to B)

Used for connecting the base kit to the Host PC, laptop, tablet or phone.

Replacement 25-way TTL breakout board lead

Used for connecting the breakout board to the rear of the BBTK.


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 for correct installation and validate latency before use.

*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.

Who are we

Founded in 2003 by a team of psychologists, software experts and electronic engineers we are dedicated to improving the millisecond timing accuracy and experimental rigor of researchers in the behavioral and brain sciences.

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