Sampling reliability measures

Functionality, Add-ons, etc.
BITalino
Site Admin
Posts: 554
Joined: Tue Aug 27, 2013 3:47 pm

Re: Sampling reliability measures

Postby BITalino » Tue Aug 30, 2016 10:37 am

Hi Ole,

That part of the code implements the bit packing processing, the result of which is a data packet as the one shown in the last page of the following data sheet (Fig. 6):
http://bitalino.com/datasheets/MCU_Block_Datasheet.pdf

Note that the size of the data packet varies according to the number of channels selected for acquisition. For the new firmware you can see additional information here:
http://bitalino.com/datasheets/REVOLUTI ... asheet.pdf

Best regards,
The BITalino Team

ole.traupe
Posts: 43
Joined: Tue Jun 17, 2014 10:50 am

Re: Sampling reliability measures

Postby ole.traupe » Tue Aug 30, 2016 11:32 am

Thank you for the additional information! Obviously, I got confused by the left-to-right order of the frame diagram.

ole.traupe
Posts: 43
Joined: Tue Jun 17, 2014 10:50 am

Re: Sampling reliability measures

Postby ole.traupe » Tue Aug 30, 2016 12:16 pm

There is still something I don't quite understand, I'm afraid. The code I posted above truncates channel 5 and 6 at 6 bit in case so many channels are actually requested (otherwise not). But I read here that on the plugged version channels 5 and 6 always have 6 bit precision:

viewtopic.php?f=1&t=82

How does that go together? Is the plugged firmware different? Is there a download section for the firmware's? I wasn't able to find it.

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

Re: Sampling reliability measures

Postby BITalino » Tue Aug 30, 2016 1:59 pm

Hi Ole,

Your interpretation of the firmware is indeed correct... channels A5 and A6 are only truncated to 6-bit only if so many channels are requested, otherwise they will arrive with 10-bit.

The description on the thread you've pointed out is considering the case where all channels are acquired simultaneously. On the data packet description of the revised MCU data sheet for BITalino (r)evolution we tried to make this more clear:
http://bitalino.com/datasheets/REVOLUTI ... asheet.pdf

Best regards,
The BITalino Team

ole.traupe
Posts: 43
Joined: Tue Jun 17, 2014 10:50 am

Re: Sampling reliability measures

Postby ole.traupe » Tue Aug 30, 2016 3:18 pm

I see, thank you.

So data from sensors connected to 5 or 6 (upper right two connectors on the board) get eventually truncated in case more than 4 channels are requested. Is that it?

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

Re: Sampling reliability measures

Postby BITalino » Tue Aug 30, 2016 3:31 pm

That's it... if only 4 channels are acquired and A5 and/or A6 are amongst them, they will have 10-bit.

If only 5 channels are acquired and A5 or A6 is one of them, it'll have 6-bit.

If all channels are acquired, A5 and A6 will always have 6-bit.

We've done this because for data packets with little over 8 bytes the communication was unreliable.

Best regards,
The BITalino Team

ole.traupe
Posts: 43
Joined: Tue Jun 17, 2014 10:50 am

Re: Sampling reliability measures

Postby ole.traupe » Wed Aug 31, 2016 8:15 am

Seems fine to me, as I would deem 6 bit resolution fit for data other than physiology.

Last question in this regard for now: with the basic Bitalino board BAT (battery) always was the 6th channel. I read somewhere in the forum (forgot where) that the plugged version does not include battery by default (due to community requests) but this can be achieved by cutting a via on the board and connecting two pins with a drop of solder. Is this correct? Would you mind posting a photo of the board with the respective positions highlighted?

Also, where can I download more recent firmware source files for the boards, also for the newer hardware editions? I would like to replace one channel with a sequence number with larger scope.

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

Re: Sampling reliability measures

Postby BITalino » Wed Aug 31, 2016 8:33 am

Indeed the 6-bit channels can be used for signals where not much sensitivity is needed, like the light sensor or the accelerometer (in many cases).

In the previous version of BITalino the battery level was indeed obtained through channel A6 for the purpose of controlling the low battery LED (in addition to providing a way of monitoring the device battery status on the target applications).

In the Plugged device it was disconnected by default in order to enable users to use A6 as an effective sensor data channel (and prevent concurrent analog inputs on that port).

You can re-connect the battery channel on the BITalino Plugged at any time, by shunting the two pads highlighted in the attached picture, although once you do that you shouldn't connect any additional sensor to that channel.

Note however that in our late-model BITalino (r)evolution, the battery level now has its own independent channel to control of the low battery LED (now channels A1-A6 are all effective sensor inputs).

If you want to have the battery level on BITalino (r)evolution you can either connect the ABAT pin to one of the analog inputs (in which case you need to disconnect the sensor connected to that input) or simply read it by using the newly introduced "status" command described here:
http://bitalino.com/datasheets/REVOLUTI ... asheet.pdf

The firmware currently being used on BITalino (r)evolution can be found on the following link, but the pin assignment has changed when compared to the original BITalino, reason for which if you're using an older model you should confirm the MCU pin assignment before flashing your device:
https://github.com/BITalinoWorld/firmwa ... revolution

Best regards,
The BITalino Team

BITalino Plugged [kit].JPG
Pads to shunt in order to have the battery level on channel A6
BITalino Plugged [kit].JPG (91.54 KiB) Viewed 2066 times

ole.traupe
Posts: 43
Joined: Tue Jun 17, 2014 10:50 am

Re: Sampling reliability measures

Postby ole.traupe » Thu Sep 01, 2016 9:58 am

Thank you for your extensive comments and the image! Seems that I've got all the info I need (totally forgot about your Github repo).

Again, thanks a lot!
Ole


Return to “Features”