Sequence nSeq

Functionality, Add-ons, etc.
an.ng
Posts: 4
Joined: Mon Oct 02, 2017 7:40 pm

Sequence nSeq

Postby an.ng » Tue Oct 03, 2017 2:21 am

We connected 3 Bitalinos to a computer and recorded them at the same time. In the txt file, we noticed that the nSeq for Bitalino-1 starts at 4 and Bitalino-2 starts at 11... Why so?

We want the data to be synchronized, so do we need to align the data according to the nSeq? or it is already synchronized?
Thank you very much.

Capture.PNG
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BITalino
Site Admin
Posts: 554
Joined: Tue Aug 27, 2013 3:47 pm

Re: Sequence nSeq

Postby BITalino » Tue Oct 03, 2017 6:49 am

Hi,

The difference between nSeqs happens because the actual recording only starts when all devices have started acquiring data.

Generally there are a few milliseconds delay between them, and in this case data from the BITalino with nSeq 0 was the last to start arriving, with nSeq 4 was the second and with nSeq 11 was the first.

In order to synchronize the devices you need to have a common marker triggered between them. This can be done with anything ranging from light sensors on two of the devices and an LED on the other, or with a synchronization cable connected between digital ports.

With this setup whenever you activate a digital output on the "master" device, this will be marked on the data from that device as an activation of the digital output and on the receivers as a change on a digital input pin or amplitude level of the analog signal (in case of the light sensor approach).

I hope you found this information useful. If you have further questions, let us know. To help in this process we have a sync cable on our store:
https://store.plux.info/cables/231-synchronization-cable.html

Best regards,
The BITalino Team

an.ng
Posts: 4
Joined: Mon Oct 02, 2017 7:40 pm

Re: Sequence nSeq

Postby an.ng » Wed Oct 04, 2017 7:31 pm

Thank you very much. We did send markers to one of the Bitalinos using the Pushbutton but we did not use the synchronization cable. The marker is presented by the I1 channel switching from 0 to 1 and 1 to 0 (photo attached). So, in this case, all the data that are in the same row with the marker are synchronized? All Bitalinos are recorded at 100 Hz.
Best regards,
Attachments
markers.PNG
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BITalino
Site Admin
Posts: 554
Joined: Tue Aug 27, 2013 3:47 pm

Re: Sequence nSeq

Postby BITalino » Wed Oct 04, 2017 8:28 pm

Hi there,

Was the pushbutton connected to all devices?

Best regards,
The BITalino Team


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