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The Various Protocols Supported by
the RB Series Response Pads
Last
Revision: March 3, 2004
The information in this
document applies to:
Owners
of an RB-530,
RB-730, RB-830, or
RB-834 response pad who want to use it with programs other than the ones listed
on the RB Series Support home page.
Summary
The RB-x30 generation of
response pads is the fourth one that Cedrus has built and supports four different protocols. This document compares these protocols.
The Available Choices
If you decide to use an RB
Series response pad with a program other than the ones described on the
RB Series Support home page, the first task is to chose
which protocol suits your application best. A protocol is simply a fancy
word for a method or format used to send the information to the host computer.
The four protocols supported
are: XID, RB Series, ASCII, and PST SRB. Each has advantages and disadvantages:
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XID (eXperimental Interface Device) |
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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. |
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Reaction
time is measured in hardware; this eliminates timing uncertainties
in Mac OS and Windows |
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You can
detect when two or more keys are pressed simultaneously |
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You can
detect when a key has been released |
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You can
detect input from the Accessory Connector |
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It takes the most
programming to handle the XID protocol |
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RB
Series |
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Each bit
within the byte indicates which key is pressed |
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One and
only one byte is sent every time a key is pressed or released |
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You can
detect when two or more keys are pressed simultaneously |
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You can
detect when a key has been released |
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It takes some
programming to decode the individual bits |
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ASCII |
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An ASCII
value is sent when a key is pressed |
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One and
only one byte is sent every time a key is pressed |
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Simplest
mode |
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You can
see readable output from the response pad using a terminal
emulation program such as HyperTerminal in Windows or VersaTerm on
the Mac |
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You cannot detect when
two or more keys are pressed simultaneously |
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You cannot detect when
a key has been released |
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PST SRB
(Psychology Software Tools
Serial Response Box) |
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Each bit
within the byte indicates which key is pressed |
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A stream
of bytes is sent approximately 800 or 1600 times per second |
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You can
detect when two or more keys are pressed simultaneously |
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You can
detect when a key has been released |
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It might take some
programming to decode the individual bits |
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The constant stream of
bytes makes it more difficult to deal with |
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Which Protocol to Use
For adapting an RB Series
response pad to your own software package, the choice boils down to XID, RB
Series or ASCII modes. We do not recommend the use of PST SRB mode 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 pad do it for you, the
XID mode is the only and best way to go.
If your experiments do not
require knowing when two keys are pressed simultaneously or when a key has
been released, then ASCII mode is the simplest and easiest to deal with.
Otherwise, we recommend that you use the RB
Series mode.
If you prefer to use the PST SRB mode, you
will need to contact Psychology Software Tools, Inc. directly for
information about their Serial Response Box Model 200 protocol.
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