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Support   SV-1    Other Resources for Communicating with SV-1

The information in this document applies to owners of an SV-1 device who want to use it with programs other than the ones listed on the SV-1 Support main page.

Available Resources

The Presentation extension (C++ code) and Python code libraries are supported by Cedrus as far as fixing bugs and providing updates.  However, we are unable to provide help in debugging your own code.

C++ and Python

Cedrus has developed Python and C++ libraries that are open sourced.

Matlab

Cedrus offers sample Matlab examples.

The Various Protocols

SV-1 supports four different protocols. A protocol simply means a method or format used to send the information to the host computer. The information below applies to SV-1 and our response pads as well.

The four protocols supported are: XID, RB-x20, ASCII, and PST SRB. Each has advantages and disadvantages:

Protocol

How it Works

Pros and Cons

XID (eXperimental Interface Device)

The computer triggers the XID device at the onset of a trial. When the subject or patient responds, the device sends back information that includes reaction time.

Reaction time is measured in hardware; this eliminates timing uncertainties in Mac OS & Windows

You can detect when two or more keys are pressed simultaneously

You can detect when a key has been released

You can detect input from the Accessory Connector

It takes the most programming to handle the XID protocol

RB-x20

Each bit within the byte indicates which key is pressed

One and only one byte is sent every time a key is pressed or released

You can detect when two or more keys are pressed simultaneously

You can detect when a key has been released

It takes some programming to decode the individual bits

ASCII

An ASCII value is sent when a key is pressed

One and only one byte is sent every time a key is pressed

Simplest protocol

You can see readable output from the response device using a terminal emulation program

You cannot detect when two or more keys are pressed simultaneously

You cannot detect when a key has been released

PST SRB (Psychology Software Tools Serial Response Box)

Each bit within the byte indicates which key is pressed

A stream of bytes is sent approximately 800 or 1600 times per second

You can detect when two or more keys are pressed simultaneously

You can detect when a key has been released

It might take some programming to decode the individual bits

The constant stream of bytes makes it more difficult to deal with

Which Protocol to Use

For adapting a Cedrus response device to your own software package, the choice boils down to XID, RB-x20 or ASCII protocols. We do not recommend the use of PST SRB protocol except with E-Prime, mainly because the constant stream of bytes can be a hassle to deal with.

If you want to offload the task of measuring reaction time and have the response device do it for you, the XID protocol is the only and best way to go.

If your experiments do not require voice key offset, i.e. when the participant has stopped speaking, then ASCII protocol is the simplest and easiest to deal with. Otherwise, we recommend that you use the RB-x20 protocol.

If you prefer to use the PST SRB protocol, contact Psychology Software Tools, Inc. directly for information about their Serial Response Box Model 200 protocol.


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Last revision: Mar 29, 2022

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