INFO: Differences between Celeritas E-Prime integration and HID [24670]

This article applies to:

Celeritas Software for E-Prime 3.0
Celeritas Software for E-Prime 2.0
Celeritas Monitor

Detail

Differences between Celeritas E-Prime integration and HID
E-Prime users planning on using Celeritas Response Devices (BRU and/or Joystick) in their experiment are strongly encouraged to use them in Celeritas mode instead of HID mode. This requires that Celeritas Software for E-Prime be installed, the Celeritas Device be added as an E-Prime Device, and that Celeritas Device Properties be used within E-Studio to configure the Celeritas Device. If Celeritas Monitor is installed rather than Celeritas Software for E-Prime, then the Response Devices can only be configured with the Celeritas Monitor software running outside of E-Prime, and the Response Devices be added as HID Keyboard, Mouse, or Joystick rather than as the custom Celeritas Device; E-Prime then interacts with these devices in HID mode rather than Celeritas mode.

Celeritas mode offers tighter integration with E-Prime than does HID mode. Celeritas mode offers both timing and data integrity advantages as well as other practical benefits. This article highlights the advantages of using Celeritas mode over HID mode.

Increased Timing Precision
In Celeritas mode, responses are time stamped with microsecond precision. In HID mode, responses are time stamped with millisecond precision. 

Increased Timing Accuracy
The accuracy of a Celeritas mode timestamp is guaranteed because the timestamp is attached to the response on the device before it is sent over USB, and the timestamp is synchronized with E-Prime to always be within 100us of E-Prime's clock. A HID mode timestamp does not have guaranteed accuracybecause random, nondeterministic delays in the OS can degrade timing accuracy without an upper bound.

Enhanced Response Information
E-Prime has access to the complete history of responses when collecting data from a Celeritas response device used in Celeritas mode. Further, Celeritas Joystick responses collected in Celeritas mode provide multiple types of cursor x information for each response; this data is not available for Joystick responses collected in HID mode. 

Enhanced Data Integrity
Data integrity is more robust in Celeritas mode for the following reasons:

• In Celeritas mode, inputs from the Response Devices are buffered with hardware timestamps and a sequence counter is used to ensure that responses are not missed. In HID mode, the host controller polls for input. Therefore, if the operating system does not check for a Celeritas response as the appropriate time, then the response will be missed. 
• Celeritas mode has a lower minimum input pulse period than does HID mode (200 microseconds for Celeritas mode versus 2 ms for HID mode). In theory, if a 1ms pulse came in with 0 debounce, the pulse might be missed in HID mode since it doesn't last long enough.

Automatic Trigger Mask Handling
When running in Celeritas mode, the Trigger Mask setting on the Celeritas Console is restored at the completion of the experiment, regardless of its use during the E-Prime experiment run. This feature is not supported in HID mode. Therefore, experiment technicians must remember to restore the Trigger Mask setting at the conclusion of the experiment when running in HID mode. Failure to do so may result in the experiment computer being flooded with the equals ("=") trigger mask character with the next run of the scanner.

Enhanced Response Mappings
Celeritas mode offers the following enhanced response mapping options:

• The Celeritas Joystick buttons can only be remapped in Celeritas mode.  Re-mapping enables the experiment to define the value that is sent for each button press.  For example, the top button on the back of the Celeritas Joystick maps to response 3 by default; this can be re-mapped in Celeritas mode to send a different response if desired. NOTE: BRUs can have their responses remapped in either Celeritas or HID mode.
• Button re-mappings for the Joystick and BRU are stored within the E-Prime experiment specification file when running in Celeritas mode. This offers true experiment portability: the same button re-mappings automatically apply when the experiment is run on any Celeritas console, since the re-mappings are part of the experiment script (ebs file). Conversely, button re-mappings that are defined while in HID mode are specific to the Celeritas console (if saved as a Console Profile) or the experiment development computer (when saved locally on the computer). Therefore, these re-mappings not “travel” with the experiment when it is run on a different Celeritas Console.
• Celeritas mode enables the Joystick resolution to be customized; these customizations are not supported in HID mode. The custom Joystick settings enable Joystick cursor movements to be scaled as needed and to be smoothed out. Joystick zones can also be defined, including movements in what would normally be a ‘dead zone’ to register.  (However, the Joystick can be configured to operate as a HID mouse, which offers some cursor movement enhancements, in both Celeritas and HID mode. )

Immediate Confirmation
When working in Celeritas mode, the experimenter sees immediate confirmation of the status of all response units; units which are not detected are visually distinct from those that are detected. Since this confirmation is not available in HID mode, there is a greater risk that the experiment session will be started with the response devices not detected.

In summary, there are numerous advantages to operating in Celeritas mode over HID mode which are detailed below.  PST always recommends that when running with E-Prime, the BRU and/or Celeritas Joystick always be operated in Celeritas mode.