SDK commands to get the data files from SD card to the computer
Hi, I'm using brainflow, Cyton and SD card to save EEG data. after stoping the data stream, are the datas still in the internal buffer? so that we can save it on our computer as well in .csv file with 250Hz? or do we
have any SDK commands to get the data from sd card right after it saves on SD card?
It just that I'm converting the data type of the EEG file and doing some post-processing with brainflow.
Sincerely,
Shyamal
Comments
The buffering on the Cyton mainboard RAM is minimal, only a sample or so until it is either sent to the RFduino radio or stored on the SD card. You are expected to remove the SD card and read it on your computer card drive. There is no SDK command to read SD card and send over the radios.
Understood, now to convert the hex values in those files we need to set the scale factor to be about 0.02235 according to this thread https://github.com/OpenBCI/OpenBCI_GUI/issues/1014 Also, according to this https://github.com/OpenBCI/OpenBCI_GUI/blob/4ab8cf7e024aed367e0cca07f02ad4e3b4366836/OpenBCI_GUI/DataSourceSDCard.pde#L287 the logic behind negative values and postive values is understood. However, I cannot figure it out how can i implement this in python to convert the whole file. I need help for this because our research need 250Hz sampling rate in order to carry on with the experiments.
https://github.com/OpenBCI/OpenBCI_GUI/issues/1014
Linking this thread and this issue. Upping the priority and planning this for next GUI which is now in active development.
Hi William,
I'm doing a measurement where the data is transferred over the radios to the computer. But the patient can sometimes leave the room and cause a disconnection of the radio signal, and then when he is back in the room the radios reconnect . I want to save the data that is lost when the radios are not connected. Is there a way to write the data to the SD card when the radios are not connected, and once they reconnect, send that data from SD card to the computer?
I know it might be complicated but I need to know if it's possible at all or not and how to try and deploy such a thing.
Thanks,
Gilad
Hi Gilad,
You are free to rewrite the firmware, but it is not recommended. The current firmware has no way of sensing if the radio channel is blocked due to dongle reception issues. The packets are just sent (pushed) from the PIC32 over a serial link to the onboard RFduino. (No feedback pathway in the event of radio failure.) And then that RFduino forwards, over the air, to the dongle RFduino. Thus it would be problematic on how the PIC32 would know to start sending to the SD card.
Additionally you have a kind of "catch 22" issue. In that the radio link, in 8 channel mode, only runs at the maximum packet rate of 250 packets per second. This radio link cannot run faster. So... If you want to "catch up" the stream, you will always be behind by the amount of time the radio link was down.
William