Using Cedrus

Last update: July 20 2022

• Cedrus_TTL.m is a function that enables hexidecimal TTL to NLX transmission during a behavioral task.
• This function is based off of the script CedrusSetup.m. The script is not needed for any of these functions to work, but just provides more detail about the code written in the Cedrus_TTL.m function.
• The source of CedrusSetup.m, getByte.m, and setPulseDuration.m can be found in support documents on the Cedrus website.

Requirements

• getByte.m and setPulseDuration.m must be on the MATLAB path for Cedrus_TTL.m to work.
• MATLAB must be opened before the Cedrus c-pod is connected to the computer from which the behavioral task runs. If the c-pod is connected before MATLAB is opened, it won't work.
• Must use MATLAB R2020a or later version

User guide

1. Assign distinct TTL markers for event types

• An example of what this would look like can be found in hexidecmial TTL key.txt.

2. Every time you wish to send a TTL, the following code should be written immediately following the line containing the event.

• Example:

        subjdata.ts.stimStart(t) = Screen('Flip',wind,[],1); %show the stimuli
        if do_TTL
            %DatapixxAOttl(); % TTL pulse marking screen flip that shows choice options
            write(device,sprintf("mh%c%c",70, 0), "char"); % TTL pulse marking screen flip that shows choice options
        end
  

Where DatapixxAOttl();, used to send TTLs with Datapixx and now obsolete, is replaced by write(device,sprintf("mh%c%c",70, 0), "char");

3. Replace the number within the sprintf call with the event marker of your choosing for every distinct event.

• In the example above, 70 would be used to mark stimuli presentation, and would be changed to a different number for a different event type.

4. Call Cedrus_TTL.m with outputs from within the main behavioral task function or script.

Note: This function needs to be called before the first time the Screen function is called if using Psychtoolbox.

• Example: [~, device] = Cedrus_TTL()