Millisecond accurate USB response pad technical specifications
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For the more technically minded, specifications for our millisecond accurate USB response pad can be seen below. We think it's important for you to have full confidence in our USB response pad when using it in your psychology experiments.

We have taken the decision to publish full technical and timing specifications for our USB response pads as all too often the equipment you use on a daily basis is of unknown quality.

In our view, if other vendors do not publish specifications for their hardware or software you should not be using it!

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Technical specifications

Physical specifications *Nominal accuracy
  • Carbon fibre effect plastic enclosure (202mm x 137mm x 35mm LWH)
  • 4x Japanese Seimitsu PS 14 GN 30mm dia buttons, overall dia 34.5 mm (certified for min 1,000,000 presses)
  • 4x Active Switch Closures (9-way D) to short out external push-to-make buttons on external equipment
  • Depending on model up to 8x unique TTL markers rather than ASC port (one per button, 9-way D)
  • 1x 2.5mm stereo socket for +5V TTL event marker on any button down
  • 4x 3.5mm mono sockets for external push-to-make button input
  • Full-Speed USB 2.0 (USB 3.0 compatible)
  • 4x unique +5V TTL event markers for use with The Black Box Toolkit v2 or other equipment (9-way D)
  • Appears to the host PC/Mac/Linux system as a standard HID keyboard (no drivers required)
  • Anti-ghosting technology means that up to 6 buttons can be held down and released in any order whilst being correctly reported to the host operating system – meets full USB HID keyboard specifications
  • Fully updatable firmware – 32K flash RAM (100,000 Erase/Write Cycles)
  • In USB response pad mode checks for a button press 50,000 times a second (50kHz sampling rate)
  • In Black Box response pad mode checks for a button press 221,000 times a second (221kHz sampling rate)
  • Typical time to recognise a button press 10 millionths of a second (10.20µs)
  • Typical time to transmit keystroke(s) to PC after detecting a button down 60-87 millionths of a second (60-8 µs) – status of up to 6 buttons/keys from 8, transmitted on first available USB packet
  • Typical time to recognize a button up 75 millionths of a second (75µs)
  • 2.5mm socket +5V TTL pulse width 50ms (interrupt driven timer)
  • 4x ASC's 0.4 ms inherent delay due to use of Solid State Relays (SSR) to protect your equipment
  • 4x BBTK +5V TTL signal matches button down onset, duration and offset
  • 25ms button up debounce (a button has to be cleanly up for 25ms before a key up signal is sent to the PC)#

#This can add 25ms to key down durations – onsets or RT's are unaffected as these are sent to the host PC immediately. ALL standard keyboards and other response boxes typically have longer debouncing periods. In addition operating systems have a set key repeat rate during which they don't accept key presses faster than a certain rate.

Remember although our USB response pads are millisecond accurate and help reduce RT variability in your experiments they can't automatically correct for any mistimings that are inherent within the experiment generator you use (key features).


In order to validate our claims for accuracy we have tested the shipping electronics and firmware thoroughly. Below are a series of screen grabs from one of our Tektronix oscilloscopes.

   
Physical button down (1) to TTL event marker (2) USB mode sampling rate, i.e. how many times a second button status is checked
   
   
Physical button down (1) to USB keystroke sent on first available USB packet to PC (2) – NB this is the worst case measure for our test PC, mean 60µs BBTK mode sampling rate,
i.e. how many times a second button status is checked
   
Physical button up (1) to TTL event marker (2) TTL pulse width