ToTaL Control System
The ToTaL Control System has been developed to provide PLATO users a flexible tool to control the opening and closing of the spectacle lenses, by means of simple TTL (0 or 5 volt) pulses. [1] The system consists of a software interface and the ToTaLcontrol Pulse Generator hardware (shown in photo). The ToTaL Control System requires a computer, with at least one USB port, running Microsoft Windows XP, Vista, 7 or 8 operating system. [2]
The system is able to generate both periodic and non-periodic series of control puls
es. Adjustable pulse parameters include Open-time duration, Close-time duration, cycle period, onset delay, and number of pulse cycles.
The left and right eye lenses can be triggered completely independently.
All trial Start and Stop times are stored on the unit’s SD card, thereby enabling post processing analysis of all visual information presentation times.
Because it has its own microprocessor, the ToTaLcontrol Pulse Generator has to be connected to the host computer only for changing the pulse generation instructions (and/or for uploading the data from an experiment). Otherwise, the pulse generator can be operated without being attached to the host computer.
There are four possible methods for commanding the pulse generator to start generating pulses:
1. Through the ToTaLcontrol software interface, with communication through the computer’s USB port. Running trials in this mode involves simple start/stop interactions through a dialogue box.
2. For more advanced users, a second software interface option involves communicating with the pulse generator through concurrent applications being run under Matlab.
3. By means of external trigger signals generated by other equipment within an experiment (such as pushbuttons, force platforms, light beams, etc.).
4. Manually, by means of pressing Start/Stop and Left/Right trigger buttons on the ToTaLcontrol pulse generator box itself.
These triggering alternatives are shown in the accompanying block diagram. For the first two modes, communication is through the USB port. For the third and fourth modes it is not necessary for the pulse generator to remain connected to the computer (other than to provide power, instead of using a 9v battery).
Three Alternative Methods for Triggering a Series of Output Pulses
Remote (Wireless) Operation
The ToTaL Control System has also been designed with the option of triggering the ToTaLcontrol Pulse Generator rem
otely. With the Pulse Generator and the PLATO Driving Circuit both operating with (9V) batteries, an experimental participant is thus free to walk around freely (while carrying both devices), without the need to be tethered to any of the fixed equipment in an experiment through a triggering cable. This operation requires acquisition of the ToTaL Remote Controller (shown in photo).
In order for the ToTaL Remote Controller to communicate with the ToTaLcontrol Pulse Generator, a (2.4 GHz) antenna must be attached to each device. The range of reliable wireless communication ranges from 5 to 50 m, depending primarily on factors such as the presence of obstacles between the two devices (including participants’ bodies), reflections from surrounding surfaces, battery strength, etc.
Because the ToTaL Remote Controller has been designed to enable the carrying out of a completely untethered experiment, the only means of activating a series of pulses is through external triggering, as shown in the block diagram below. For this mode of operation all manual inputs to the Pulse Generator are de-activated, to prevent inadvertent activation by experiment participants . There is also no means for controlling the system through the computer interface in this mode of operation.
Wireless Operation Mode, Showing External Trigger Activation and Communication Through Antennas
For clarification(!), a comparison of the non-wireless and wireless modes of operation is shown photographically below.
Comparison of Wireless and Non-wireless Operating Modes for External Triggering
[1] Although our primary objective has been to provide control signals for the PLATO visual occlusion system, the device can also be used as a generic programmable dual channel TTL pulse generator.
[2] More precisely, the software will run on any Windows operating system that can run the .NET framework 4.0. This does not include Windows 95, NT Server, or Server 2003 for Itanium based systems. Our experience has also been that the software functions well when using Windows emulation software, such as Parallels, on a Mac.