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[How-to] use a digital sensor together with a push button for marking events?

biosignalsplux includes a diversified set of analogical and digital sensors on his catalogue (for more information please check the list of available sensors ).

Currently, with a single hub, it is possible to collect data from 4 to 8 analogical sensors simultaneously and in a totally synchronised way, taking into consideration the available hubs (4 or 8-channel hub).

This interesting number is extremely useful on researches where a coupled analysis of data from different origins is needed, for example, during a sports activity, may be useful to understand how heart rate changes and which is the contraction intensity of some muscles, something achievable through biosignalsplux, 1 ECG sensor and 1 EMG sensor per muscle under analysis.

But, you can go a little further and expand your biosignalsplux experience by pairing three hubs together (using PLUX synchronisation kit providing a way to do acquisitions with up to 24 analogical channels.

However, for working with digital channels there are more restrictions (for now ;) ), taking into consideration that a hub only includes 1 or 2 ports with a digital functionality (as demonstrated on the figure below for the orange and red labels).
biosignals | biosignalsplux digital ports.

In the current discussion it will be explained how to get the most out of the two available digital ports, through an illustrative example.

Imagine that you need to collect Functional Near-Infrared Spectroscopy (fNIRS) data , trigger the start of acquisition with a push-button and also mark some additional events during the acquisition... that is possible as it will be demonstrated !

1 - Sensor Connection
The first step that must be followed refers to the connection between fNIRS sensor and biosignalsplux hub.
You should connect the fNIRS UC-E6 plug to the bottom left port of biosignalsplux hub (Ground/Digital Port), as demonstrated on the following figure:
biosignals | connection between the fnirs sensor and the hub

2 - Push-Button Connection
Connect the push-button UC-E6 plug to the synchronisation/native digital port of biosignalsplux hub.
biosignals | connection between the push-button and the hub

3 - Configure OpenSignals
3.1 - Enable your device
biosignals | enable biosignalsplux device on the opensignals interface

3.2 - Activate Channels 9 and 10
biosignals | definition of the active channels

3.3 - Specify "fNIRS" sensor on the previously activated channels
biosignals | specification of the sensor type

3.4 - Activate the "TRIGGER" option (with this functionality we ensure that the acquisition will only start when the push-button connected to the "SYNC" port is pressed)
biosignals | activation of trigger functionality

4 - Start of the Acquisition
4.1 - Click on OpenSignals "REC" button
biosignals | start of a real-time acquisition

4.2 - Press push-button for triggering the start of acquisition
biosignals | triggering the start of data acquisition

5 - Mark Events
5.1 - Press the push-button every time you want to mark an event
It should be taken into consideration that we cannot see the events on the real-time timeline. However every time we "mark" an event the "DIGITAL INPUT" indicator on OpenSignals interface will become blue
biosignals | marking events with the push-button

Change on "DIGITAL INPUT" indicator when an event is marked:
biosignals | demonstration of event recognition on opensignals

6 - Access to the Marked Events
On the OpenSignals visualisation environment it is possible to see the marked events on the digital output channel.
biosignals | check the digital events triggered by the push-button

All this marked events are included on the acquisition files generated by OpenSignals as demonstrated on the second column of the .txt file presented on the following animation.
biosignals | stored events on opensignals files

The previous steps are a good example of how to combine two digital ports on a single acquisition and using only one device. Other combinations are possible, but many of the described principles remain the same.

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