Set up TTL in Neurobs Presentation with Smarting Pro

Jelena Mladenovic

Jelena Mladenović, PhD

September 9, 2022

If you are up for an EEG experiment which requires offline recording – for example, record EEG in the woods where there is no internet connection, so you’re recording EEG on an SD card; Good news – you are in the right place! In this blog, we will walk you through a way to set up TTL in Neurobs Presentation software, using cable triggering and Smarting PRO mobile EEG.

Smarting Pro supports TTL input of 1 bit. It is a cable that is plugged, on one side, into the amplifier (as an audio jack of 2.5mm) and on the USB port of a computer on the other side. Below you will find an example of setting up TTL in Neurobs Presentation.

How To

  1. Windows 10, 64bit (in this example we used Windows but check if it applies to other platforms)
  2. Install drivers for TTL, download here. 
  3. The TTL cable that Smarting Pro uses is this one.
  4. Install Neurobs Presentation 

You should have an experiment scenario already made in Neurobs Presentation or you can use this simple one (mbt sound example). Note that the experiment file (.exp) keeps the path of the computer it is saved on, and the ports it used. To solve this problem, just save it as a new experiment with Save As in Presenter. But before saving, make sure you have changed the Port Settings in the Presenter, as follows.

Fig 1. TTL setup (left), Windows Device Manager (right).

Then go to Presentation->Settings, Add an OUTPUT Port, because you are sending triggers from the computer to the EEG amplifier. Note that this applies to any other output (cable) using serial port, not only TTL.

Fig 2. Adding the output port in Presentation.
Fig 3. Filling the values for TTL.

After you have filled in the values like in the Figure above, just click on Close.

Some useful info about setting the ports in Neurobs Presentation can be found on their website: Output Port Settings, Event Port Output

Finally, if you want to use the demo examples from Presentation, like the well-known N-Back task, simply add the port as indicated earlier, and Save As new experiment file (it will modify the .exp file with the correct port and path).

TTL is “physically” marked onto the EEG data with minimal delay and can be recorded directly onto the SD card of the amplifier together with the EEG. Additionally, they can be both sent together back to the computer (mbt Streamer) via Bluetooth. In that case, open and connect the mbt Streamer to allow receiving EEG streams on your computer (capturing bluetooth packets). You can also see TTL triggers marking EEG signals in real-time on mbt Streamer. TTL protocol facilitates the integration of embedded systems e.g. it could send events from the Arduino board (using a serial communication).

Fig 4. To test if TTL is working, simply look at the EEG signals in real time in the mbt Streamer, and Send Test triggers from Presentation.
Fig 5. Every time you press Send (simulating a stimulus), in real time you can see a vertical line appearing in the EEG signals within the mbt Streamer with no delay. Do not mind the EEG signals, the cap is not even placed on the subject’s head.
Fig 6. Remember in mbt Streamer to click ON for TTL markers if you wish to record them also as LSL markers. In that case, you will have EEG streams, and TTL triggers as LSL.
Fig 7. Depicts the path of TTL triggers and EEG. (1.) triggers are sent from Neurobs Presentation for each stimulus via TTL cable to Smarting PRO amplifier, instantly marking the EEG streams “physically”. (2.) EEG streams (with triggers) are streamed via Bluetooth back to the computer where (3.) they are converted into LSL streams and sent to the network as multicast LSL protocol to be received by any other computer on the same network.

This way you can see how TTL markers, once physically integrated into the EEG, are streamed along with the EEG signals through bluetooth and converted into LSL streams.

Conclusion

Let us know how it goes and if you have any questions feel free to reach out to us on our contact page.

*Conclusion written by mbt team

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