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Page Revision: 2015/01/27 03:08

Cedrus XID element monitors button and line states on the Cedrus input devices that support the XID (eXperimental Interface Device) protocol. The supported XID devices include the RB Series and Lumina response pads, StimTracker marker and SV-1 voice key.

Table of Contents [Hide/Show] Actions aligned with epochs of the parent event Properties     Generic Properties Description Supported Cedrus devices (with links) Selection of the monitored button or line Triggering modes Button Names Triggered Snippet Practical Use     Technique 1     Technique 2 Notes

Description ¶

The Cedrus XID element monitors a state of input device and collects accurate timing statistics of button presses, button releases and changes in the device's auxiliary input lines. The element uses an internal timer of Cedrus hardware (when available), which allows to record more accurate response times than when a standard keyboard is used. Multiple Cedrus XID element elements can be used to record from one or several input devices in parallel. The Cedrus XID element monitors button presses only within a scope of its parent event and return timing statistics relatively the onset of the parent event.

Supported Cedrus devices (with links) ¶

RB Series response pads

MRI compatible Lumina response unit

StimTracker marker unit

SV-1 voice key unit

Selection of the monitored button or line ¶

Cedrus XID element can monitor either one specific button or line, or all buttons and lines in the same time (when 'Any' Button is selected in the Monitored Button property). In many experimental tasks, e.g.2AFC, there are two response buttons for a participant. Due to flexibility of the Cedrus XID element, for the 2ADC tasks you can use different design patterns:

1. Create two Cedrus XID elements, each monitoring one of the predefined response buttons or lines
2. Create one Cedrus XID element monitoring Any button and write code that checks what button is pressed. The name of the pressed button is returned by the Triggered Button property
   

Both patterns are eligible. The first pattern allows to automatically ignore presses of irrelevant buttons. The second pattern is more convenient for collecting a reaction time in trial, because you can get from a single proxy variable link to the Triggering Time property of Cedrus XID element.

Triggering modes ¶

The Cedrus XID element can detect any button state, not only presses. There are 5 'triggering' modes, in which the element can operate. You need to select the triggering mode in advance, according to your requirements:

• First Press Only
• First Release Only
• Multiple Presses
• Multiple Releases
• Holding Down
  

Depending on the working mode, the element becomes 'triggered' when a specific input pattern is detected. The First Press Only mode is the default choice for registering the fastest reaction time, because in this mode the element picks up the first button press ignoring the rest. Other modes are self-explanatory, save for the holding down mode, which detects continuous presses, commonly used in the game-like activities.

Button Names ¶

The Cedrus XID uses a simple button naming, based on the button index: "Button 1", "Button 2" and so on. The input lines are named similarly: "Line 1","Line 2" and so on. Be aware that you need to maintain capital letter in the names, while operating on them in C# code. You can easily find out the actual button name, using the design-time press detector on the Cedrus XID element. Open an editor for the Monitored Button''' property and move the mouse cursor over the picture with a web. Then, press the desired button and check its name in the top row:

Using the press detector to set the monitored button or find out the button name

Triggered Snippet ¶

The button element can invoke custom user code each time, when it becomes triggered (e.g. on a button press). To engage the triggering snippet, open it via the snippet panel and write your code there. Note that the triggered snippet is invoked only once, on the first press, when the 'First Press Only' triggering mode is selected. The triggered snippet can be used for checking a name of the pressed button:

if (TriggeringButton=="LeftArrow")
    Positon.X=PositionX-1;
if (TriggeringButton=="Right")
    Positon.X=PositionX+1;

Practical Use ¶

Technique 1 ¶

1. Step 1
2. Step 2
   

Technique 2 ¶

1. Step 1
2. Step 2
   

 // Check the trial outcome. Result and RT just other user variables
// insert code snippet here..

Notes ¶

• Insert Notes here..
• Insert Notes here..