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Page Revision: 2015/01/16 12:40

HID Input element detects button presses/releases on HID (Human Interface Devices) and monitors changes in device's analog axis. The HID devices include the keyboards, mouses, joysticks, gamepad and some response boxes. If you need to record keys on primary input devices, e.g. on the system mouse, use the Button element for slightly better timing. The HID Input element collects accurate timing statistics of key presses and releases and changes in analog axis, hence, it can be used for recording reaction time of participant responses. Multiple HID Input elements can be used to record for one or several input devices in parallel. The HID Input element monitors an input device only within a scope of it's parent event and return local timing statistics, e.g. a press time as the number of milliseconds since the onset of the parent event.

Table of Contents [Hide/Show] Actions aligned with epochs of the parent event Properties     Generic properties Selection of the monitored button Triggering modes for buttons HID Button Names Triggered Snippet

Selection of the monitored button ¶

The HID Input element can monitor either one specific button, or all buttons 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. Given flexibility of the HID Input element, for the 2ADC tasks you can use different design patterns:

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

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 the button element.

Triggering modes for buttons ¶

When monitoring buttons, the HID Input element is not limited to registering just button presses. There are 5 'triggering' modes for buttons, in which the HID Input 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 ignores all successive presses. Other modes are self-explanatory, save for the holding down mode, which detects continuously presses, common in the game-like activities.

HID Button Names ¶

The HID Input element uses the button naming defined by an HID device. For example, the keyboard number buttons in the horizontal row are denoted as 'D1','D2'..'D0'. Other HID devices name their buttons as: 'Button 1', 'Button 2' and so on. Be aware that you need to maintain capital letter in the button names, when operating with them in C# code. You can easily find out the actual button name, using the design-time press detector on the HID Input 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 HID Input 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=="NumPad4")
    Positon.X=PositionX-1;
if (TriggeringButton=="NumPad6")
    Positon.X=PositionX+1;