Communication between Bitalino and OpenSignals

Bluetooth, USB, UART, Storage, etc.
biotech
Posts: 5
Joined: Mon Nov 03, 2014 3:19 am

Communication between Bitalino and OpenSignals

Postby biotech » Mon Nov 03, 2014 4:00 am

Hi there,

I'm new with Bitalino and I need some help to understand the way communication takes place. ¿Can someone tell me please if the Bitalino sends digital or analog outputs to OpenSignals?

Thanks!

BITalino
Site Admin
Posts: 567
Joined: Tue Aug 27, 2013 3:47 pm

Re: Communication between Bitalino and OpenSignals

Postby BITalino » Mon Nov 03, 2014 9:39 am

biotech wrote:Hi there,

I'm new with Bitalino and I need some help to understand the way communication takes place. ¿Can someone tell me please if the Bitalino sends digital or analog outputs to OpenSignals?

Thanks!


Hi there,

Although the sensors have an analog output, the data is sampled and transmitted as digital codes produced by the ADC on the MCU block. Both OpenSignals and the APIs typically receive those digital values by default.

On OpenSignals you can choose to visualize the data in the corresponding units, however the raw data is always recorded as digital values. To convert from the digital values to the corresponding units please refer to the following thread:
http://forum.bitalino.com/viewtopic.php?f=12&t=128

Do feel free to contact us for any additional information you may need.

Best regards,
The BITalino Team

biotech
Posts: 5
Joined: Mon Nov 03, 2014 3:19 am

Re: Communication between Bitalino and OpenSignals

Postby biotech » Mon Nov 03, 2014 3:25 pm

Thank you so much for your answer and the very clear explanation. Very useful also the link to the related thread with the conversion formulas.

So to see if I got it all right, both OpenSignas and the APIs have a DAC system to convert the digital outputs from the Bitalino to analog values. Right?

Thanks again!

BITalino
Site Admin
Posts: 567
Joined: Tue Aug 27, 2013 3:47 pm

Re: Communication between Bitalino and OpenSignals

Postby BITalino » Mon Nov 03, 2014 4:27 pm

Hi,

What OpenSignals and some APIs implement are the transfer functions (the ones listed on the other thread we've shared) that convert the digital codes from the ADC to the real units.

Still, the most feasible way for you to have (on a computer) an approximation to what would be the original analog value is to interpolate from the digital points collected with the device: http://en.wikipedia.org/wiki/Interpolation

This is not particular to BITalino; if you think of it, analog values exist for the smallest fraction of time you can think of, therefore being virtually impossible to record a true analog signal on a device with limited storage capabilities such as a computer or mobile phone.

What BITalino and devices alike do (even for audio, video, etc.), is sample the signals and quantise them to create discrete series of digital values. In the case of BITalino you can sample signals at up to 1000Hz (1ms time division) and 10-bit resolution (1023 digital values).

A device capable of sampling at higher rates and with higher resolution will give you more points on discrete series, but not the analog signal. From the discrete series of digital values what one can do is map each value to the corresponding physical unit (e.g. 0 maps to -1.65mV and 1023 maps to 1.65mV on EMG data).

This mapping results from the characteristics of the analog signal conditioning front-end on the sensor, in particular the offset, gain, and operating voltage, as you can see from the transfer functions.

Please accept our apologies in case you find our explanation to be too elementary, but the resulting text is suitable for users with different degrees of expertise. Do contact us for any further question you may have.

Best regards,
The BITalino Team

biotech
Posts: 5
Joined: Mon Nov 03, 2014 3:19 am

Re: Communication between Bitalino and OpenSignals

Postby biotech » Mon Nov 03, 2014 5:59 pm

The explanation given was great!

Thank you so much again for helping me to understand how it works.


Return to “I/O”




cron