Higher sample rates / sample at 2000hz to SDcard?
tskips
Denmark
So... i am aware that the higher sample rate discussion has already been mentioned in a few threads, and i am sorry if this all should be obvious to me.
I do really wonder though, whether it would not be possible to drastically increase the sample rate, if one chose to only use one or two channels?
And if so, how would one go about telling the ADS1299, to only process data from channel 1 and 2 ?
I do really wonder though, whether it would not be possible to drastically increase the sample rate, if one chose to only use one or two channels?
And if so, how would one go about telling the ADS1299, to only process data from channel 1 and 2 ?
Comments
Thanks a lot for the detailed reponses. I see now that i should have given a little more detail, as too what i wanted: i am currently trying to look at BAEP's which requires a sampling frequency of at least 2000 Hz (i'd like 3000).
As the AD12199 has the max sampling frequency of 16000 Hz, this leads to the necessity of reducing the amount of channels no matter what. I'll surely look into the wifi shield and the other possibilities but these will not solely be able to solve the problem.
But if i for an instances merely wanted to transfer 2 channels to an sd card, could you give me a few hints as to where in the code to look? (I quess i'll avoid interfacing with any software which expects 8 channels in this way ?)
(I will be looking at the other forum posts regarding the SD card, after posting this comment, but nonetheless i don't think the channel reduction question has been asked before, if so i am sorry)
Best regards
Tobias
First i did as follows:
- overwritten the SD card using the sd formatter software
- followed the "Cyton Board Programming Toturial", to upload the 3.0.0 code.
secondly, as it didn't really work out for me, i also did the following
- downloaded the newest GUI
- as the "~"-sign is badly accessible in the danish keyboard layout, i've changed the following in the "OpenBCI_32bit_Library_Definitions"
To
Now, the problems i had after both the first and the second time was, not being able to pres "~ ~" or "f f" and get the sample rate. (And neither getting any response when doing "~ x"/"f x" (where x is a number))
and not being able to save anything useful to the sd card, whenever i press "a", it just sorta freezes up for a second and the EEG graph in the gui is then updated extremely slowly.
The resulting data whether i let it run for 5 minutes or just stop it right away is shown in the attached screenshot.
Whenever i try to convert the sd file through the OpenBCI_Gui run with Processing (Choosing Playback(from file) -> Select SD File), Processing delivers the following error "NumberFormatException: For or inputstring: "8���...."
Would any of you happen to have any advice, as too what to do next ?
(the screenshot can be found at: https://ibb.co/iSAt7k)
I changed : "#define OPENBCI_CHANNEL_OFF_1 '1'"
To : "#define OPENBCI_CHANNEL_OFF_1 '9'"
Now when pressing 9, channel 1 turned off, indicating that the code was uploaded correctly.
but when clicking "f 2" it merely turned of channel 2...
have i misunderstood the whole "f + number" thing. (I'm currently pressing and not holding f, then pressing and not holding a number) .
I got it working now through Arduino IDE.
The output file on my SDcard doesn't change though, it still seems rather unlike the sample data in the guide.
I can't seem to find any "attach file" feature?
and again! thanks a lot! I really appreciate your effort!
https://drive.google.com/file/d/0B90vk1SBDiruSGUzaU1sNXdScFU/view?usp=sharing
I'm sorry to say that i don't remember which ones where recorded under which circsumstances.
The one that looks the most like what i've commonly seen is this one:
https://drive.google.com/open?id=0B90vk1SBDirubVp4ZElneUJTXzA
I do not know where to verify if that is the beta2 version.
I should mention though that this problem did seem to persist from before i uploaded the v3.0.0 firmware to the board,
which makes me wonder whether the cause is actually something about the sd-card... (my current one is a 16 gb samsung, class 10, uhs speed 1)
I'll try testing with another one, as soon as i've found one, on of the next days.
I am back and sorry about the long delay.
I have now re downloaded the v3.0.0-beta2, uploaded this to the board and gotten myself a brand new Class 10 micro SD, which have been formatted twice with the SDFormatter application before use.
Using the arduino serial monitor i then firstly sent "~1" to change the sample rate.
next send "a", to record signal, followed by "j", after some time.
next i changed the sample rate back to 250Hz by sending "~6"
and send "a". which resulted in an error, which can be seen in the following log:
https://drive.google.com/open?id=0B90vk1SBDiruZGdzbGR6RjVKNEU
The first file was empty/filled with blanks, and so it seems impossible for me to derive anything from this.
Should i move this to a new thread?
i then proceeded the same way as above.
I did this four times, the first three were blank, the fourth 8000 Hz was blank, but the 250 Hz recording was this:
https://docs.google.com/document/d/14-zUbAzOigYmWnGdEaJucfVBhH7BCHIcxk_Xl3E5Pck/edit?usp=sharing
But once again i would like to mention that this problem persists from when i was using v2.x.x.
i just tried a fresh download of:
OpenBCI_32bit_Library v2.0.1
OpenBCI_32bit_SD
and uploaded these to the board, the results are exactly the same.
EDIT:
I did this, thinking that the 2.0.1 build would be stable and tested, dont hesitate to tell me if my reasoning is off here.
1. Yes. Looking to release a 3.0.0 release candidate by end of week which supports wifi. I had to rip out the whole back end of the GUI lol and moved all mission critical board connections to an electron hub. So now a single cross platform sub app serves the data for cyton, ganglion and both over wifi.
2. It's open source, there are tons of examples of UDP on ESP8266 Arduino (some nice Google terms right there!) But udp is too basic for a reliable connection after testing and testing so I didn't want to focus on it for the 1.0.0 release. There is an open issue for adding udp support on GitHub, you should comment on that too track whenever the feature is added. I must admit, I NEVER thought of using udp as a stimulus channel, that's pretty dang interesting!
One more question, since the wifi is so much faster than the serial bluetooth would it be appropriate to add a "marker" channel to the data now - just a simple int. If we do it now then all the raw data files will have the correct format. If we don't then we need some way to identify whether a new stream has a marker or not.