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Page Revision: 2014/04/12 21:50

LPT Port port element allows sending and receiving data via the parallel port (LTP) of a PC computer. The element can be used in standard experimental tasks, for example, for sending synchronization triggers to an EEG recording station.

Table of Contents [Hide/Show] Description Snapshots Practical Use     Manual I/O working mode     'Auto-output on event onset' mode     'Triggering on specific input' mode Notes Synchronized Internal Actions Generic Properties

Description ¶

The LPT port element allows the use of the parallel port (LTP) on PC computers for bidirectional data exchange. The LPT port can be described (at the software level) as a simple digital device that has 8 input and 8 output lines. Each line is binary, such that the ON/OFF status that can be set (for the output lines) or read (for the input lines) at any moment of time. Simplicity and instant access of the LPT port make it very useful in experimental scenarios that require a precise synchronization between experimental events and external hardware.

Snapshots ¶

Practical Use ¶

The parallel port element supports 3 different working modes. In the Manual I/O mode you have direct access to digital lines of the parallel port via the Input Value and Output Value variables and can program communications manually. In other working modes the element performs communications automatically such that no or little coding is required.

Manual I/O working mode ¶

In this mode the element can be used to send and receiving digital codes manually through the LTP port, at the desired moment. The element has two properties: [Input] and [Output]. These are linked to the current input and output of the parallel port correspondingly. The current port input can be always accessed by reading a value of the [Input] property in your code snippets. Note that any changes of the port input between two subsequent property readings cannot be tracked in this working mode. Assigning a value to the [Output] property in code snippets causes an instant update of the port output lines with the new value.

'Auto-output on event onset' mode ¶

In this mode the element sets the port output lines synchronously with onset of the parent event. The status of each output line is chosen according to the current value of the Output Value property, for example "00101101". A new value can be assigned to the Output Value at any runtime moment, but it does not causes an instant update of the output lines, as in the Manual I/O Mode. The element will wait for the next onset of its parent event to set the port line. This working mode is handy when you need to send an instant trigger to an external device every time, when some event occurs in an experiment. For example, if event contains a visual stimulus and the Parallel port element, the trigger will be sent as the stimulus is presented on the screen. You also can select a shape of such output signal in time relatively to the duration of the parent event:

1. Level signal shape. If this signal shape is selected, the element simply sets the output lines of the parallel port to the value defined bythe Output property synchronously with activation of the parent event.
   
2. Pulse signal shape. If this signal shape is selected, the element performs a signal synchronization program consisting of 3 steps. Shortly before activation of the parent event the port output is set to the ground (each line is Off) level. When the parent event is actually activated the element sets the port output lines to the value defined by the [Output] property. Later, after a time interval defined by [Pulse Duration] property, the element sets the port output back to the ground. If the pulse duration is greater than the actual duration of the parent event, the element grounds the signal pulse at deactivation of the parent event.
   
3. Trigger signal mode. If this signal shape is selected, the element performs a signal synchronization program consisting just of 2 steps. Shortly before the parent event is activated the element sets the current port output to the ground (zero) level. When the parent event is actually activated the element changes the port output to the value defined by Output property. Subsequent port output changes can be done only with other parallel ports elements.
   
   

Notice that the element in this working mode has an action scope. This means that the output can be set only when the parent event is activated.
Note, for output information, please see Output.

'Triggering on specific input' mode ¶

In this working mode the parallel port element monitors one or several input lines of the parallel port in order to detect their changes into a specific binary state. The monitored lines and their sought states are defined by the [Trigger Value] property of the element. The element alerts a successful detection by switching to the triggered state. The element triggering is always accompanied with recording of the exact trigger time and executing of the dedicated code snippet (if present). Thus, you can use a specific port input for controlling the flow of your experiment, performing custom actions and collecting accurate input timing. Notice that the element in this working mode has an action scope. This is the input monitoring and triggering are possible only while the parent event is active. However, you can always share the same parallel port among multiple parallel port elements, and each element would seek for its own triggering input. The elements also can be set to have multiple triggering in case in the port input may contains multiple occurrences of the trigger string (by default, in this working mode the element is triggered only once on the first triggering input arrival).

Notes ¶

1. You can use multiple parallel port elements in your experiment but, if they share the same hardware port, you should take in account and resolve possible interferences, like tracking the actual status of output lines that cannot been read directly.
   

1. For better synchronization of the port output (in AutoOutput and InputTrigger modes) move the Parallel Port element at the top of the elements list in the parent event. Elements there get to work one by one, as soon as the parent event is activated, so the top position in the list will minimize possible delays.
   

Synchronized Internal Actions ¶

Mode	Experiment Start	Parent Event Onset	Status change between Onset/Offset	Parent Event Offset	Experiment End
Manual (output)		Becomes ready for output.	If sentNow = True, then at this moment the output value is transmitted via the port.	Deactivates
Output on event Onset		Transfers output values over the ports.
Input Listener		Starts to listen to the input ports.	By default, the element listens to any signal and gets triggered as soon as it receives a signal. If a mask is set via the triggering input property, then the element gets triggered upon receiving the desired input signal (as defined by mask).	Stops listening.

Generic Properties ¶

Name	Description	Constraints	Value Type	Upon Runtime Change
Port Settings
Output Address	Address of the output gate in the parallel port. Default is 0x0378 (888)	Design Time..	Int32
Input address	Address of the input gate in the parallel port. Default is 0x0379 (889)	Design Time..	Int32

+=== Properties inherited from clParallelPortElement === Inherited properties of clParallelPort

Name	Description	Constraints	Value Type	Upon Runtime Change
Port Settings
Working Mode	Defines a working mode for the element.Select the 'Output on event onset' mode for sending signals synchronously with an onset of the parent event,or 'Triggering on input' mode for catching the particular pattern in port input. For custom reading/writing scenarios use the 'Manual IO' mode, in which port communications can be controlled by your code.	Design Time..	Int32
Output
Test Output	Sends a test output signal through the port using the selected signal profile and the current Output Value.	Designtime Command..
Signal Profile	Defines the time-amplitude profile of the output signal. The 'Level Change', 'Pulse' and 'TTL' profiles are available. Last two can be used to send the EEG triggers.		Int32
Preface Duration	Defines the duration (ms) of the guarantied zero preface interval for the TTL or Pulse signals. Increase the preface duration marginally, if your recording hardware does not detect port signals. Note that a non-zero preface delays the onset of the actual signal.		Double
Pulse Duration	Duration of an output pulse in ms. The value is applied only, if the Pulse signal profile is selected.		UInt64
Output Value	Value to be sent through the port. Can be defined in integer or binary format, e.g. Output='01010000'; or Output=255;		clBinaryInteger
Send Now	Runtime command that that initiates an instant transfer of the current output value through the port. Manual command calls at runtime are only required, if the element works in the Manual I/O mode.	Runtime Command..	Boolean	Execute the command by assigning true in code: SendNow=true;
Input
Test Input	Open a input monitor window showing real-time port input with the current settings. Use it for testing at designtime.	Designtime Command..
Input Value	Returns the current state of the port input lines. The property is not updated automatically. Manual reading of the property value in snippets is required to obtain the current input. The value can be read either to the integer or binary formats, e.g. 'string S=Input;' may return '01010101'.	Status..	clBinaryInteger
Triggering Input	eturns the current state of the port input lines. The property is not updated automatically. Manual reading of the property value in snippets is required to obtain the current input. The value can be read either to the integer or binary formats, e.g. 'string S=Input;' may return '01010101'.		String
Trigger Once	Returns the current state of the port input lines. The property is not updated automatically. Manual reading of the property value in snippets is required to obtain the current input. The value can be read either to the integer or binary formats, e.g. 'string S=Input;' may return '01010101'	Design Time..	Boolean
Runtime Status
Is Triggered	Indicates whether the element has been triggered at least once, since activation of the parent event. Triggering occurs only in the 'Input Detection' working mode.	Status..	Boolean
Trigger Time	Indicates the local event time of the last element triggering. Triggering occurs only in the 'Input Detection' working mode.	Status..	UInt64

+=== Properties inherited from clElement === Inherited properties of clElement

Name	Description	Constraints	Value Type	Upon Change
Control
Is Enabled	If set to false the element is completely omitted when the experiment is run.	Design Time..	Boolean
Title	Title of the element.	Design Time..	String