RB-x40 + m-pod: event markers from task computer via usb?

We have an RB-840 that I’d like to use with a biosemi eeg setup. If we use a m-pod, I gather TTL will be sent for photo sensor or button press (as configured by Xidon?).

But we’ll lose the task PC LPT->biosemi receiver connection currently used for event specific triggers (e.g. left sided event vs right sided event). In it’s place, we would send USB event markers to RB-840 which would forward them onto the EEG recording via the m-pod+biosemi receiver.

  1. Is that roughly (usb->RB->mpod) correct?
  2. how are usb markers typically set for RB-x40? In python, I see set_digital_output_lines – is that the right place to look?
  3. If we need to set USB markers, are we restricted to running the response box in more advanced modes? (would be ideal to run as ASCII if m-pod is already handing precision timing for photo & buttons within the recording)
    • otherwise, are there any hurtles to both watching for button pushes (check_for_keypress?) and simultaneously setting USB event markers?
  4. Our task event markers currently run 0-255. pin config screenshots look like we’d loose a bit for each button and photo sensor we want to uniquely identify. The biosemi receiver and stim channel are both 16-bit. Is m-pod/Xidon capable of allocating all 16-bits – can we keep our tasks’ current event marking scheme?
    • esp for start and stop triggers and legacy tasks


Hello Will,

  1. The approach you describe is correct. There is another approach but it’s more expensive because it involves purchasing a StimTracker Quad and this external TTL input kit. With this approach, you don’t have to rewrite your existing code. See Using an External Input Source.

  2. I’m not a Python programmer but that sounds correct. We can provide tech support if you get stuck.

  3. Alas yes, if you want to send event markers via USB, the response pad can be only in XID mode. ASCII mode will not work unless you use the StimTracker Quad approach. There are no hurdles to watching for button presses and setting USB event markers simultaneously.

  4. Yes, we support all 16 bits.

Let me know if you have further questions.

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