Openbci_gui: Unexpected error during push_chunk: The number of buffer elements to send is not a multiple of the stream's channel count.

[athanoid]

Problem

I have connected the Pulse Sensor and it is working fine in the GUI. I can see the analog signal and the BPM.
However, when I try to send the pulse data via LSL, I get the following error:

Unexpected error during push_chunk: The number of buffer elements to send is not a multiple of the stream's channel count.

From what I understand, probably the lsl code is expecting more channels?

Expected

Stream Pulse Sensor data via LSL

Operating System and Version

Ubuntu 20.04 - 64bit

GUI Version

v5.0.2 - 2020/12/16

Running standalone app

Running the standalone app.

Type of OpenBCI Board

Cyton

Are you using a WiFi Shield?

No

Console Log

Unexpected error during push_chunk: The number of buffer elements to send is not a multiple of the stream's channel count.

[retiutut]

@athanoid Can you please provide the full console log?

[retiutut]

I was not able to replicate this issue with push_chunk, but I did have issues with the Pulse Widget itself in 5.0.2. Thank you for making this issue!

It may be time to update the Pulse Widget...

-RW

[wjcroft]

Is the issue in the Pulse Widget, or the Networking Widget?

[retiutut]

• Pulse Widget in GUI v5.0.2 does not function properly, as seen in GUI v4.2.0.
• I received 0 data using LSL Networking Test Script (found in this repository) from Pulse Sensor data type in Networking, even with the widget opened.
• Output promised in Output Guide for LSL is not happening right now for Pulse Sensor (should be 3 values)

Maybe I did something wrong, so I will test on other computers also.

Initially, it looks like the BPM processing is happening too often or not enough, and this jacks up the data that would come from the widget. This is related to NodeJS Drivers -> BrainFlow transition in the GUI.
🛠

[athanoid]

* Pulse Widget in GUI v5.0.2 does not function properly, as seen in GUI v4.2.0.

* I received 0 data using LSL Networking Test Script (found in this repository) from Pulse Sensor data type in Networking, even with the widget opened.

* Output promised in Output Guide for LSL is not happening right now for Pulse Sensor (should be 3 values)

Maybe I did something wrong, so I will test on other computers also.

Initially, it looks like the BPM processing is happening too often or not enough, and this jacks up the data that would come from the widget. This is related to NodeJS Drivers -> BrainFlow transition in the GUI.
hammer_and_wrench

Thanks for looking at it.

Will it be also possible that the 3 channels sent via LSL, namely: raw signal; BPM and IBI are using different sampling frequencies and the LSL stream is instantiated with a fixed one? (125hz)

[retiutut]

@athanoid It is still important to have the full GUI console log. Can you please provide one?

[athanoid]

@athanoid It is still important to have the full GUI console log. Can you please provide one?

oops, here it goes:

Console Log Started at Local Time: 2021-01-18_16-18-11
Screen Resolution: 1920 X 1080
Operating System: Linux
Welcome to the Processing-based OpenBCI GUI!
For more information, please visit: https://openbci.github.io/Documentation/docs/06Software/01-OpenBCISoftware/GUIDocs
OpenBCI_GUI::Setup: GUI v5 Sample Data exists in Documents folder.
ControlP5 2.3.1 infos, comments, questions at http://www.sojamo.de/libraries/controlP5
TopNav: Internet Connection Successful
Local Version: v5.0.2, Latest Version: v5.0.2
GUI is up to date!
The file "/root/Documents/OpenBCI_GUI/Settings/UserPlaybackHistory.json" is missing or inaccessible, make sure the URL is valid or that the file has been added to your sketch and is readable.
OpenBCI_GUI::Control Panel: Playback history file not found or other error.
null
OpenBCI_GUI::Setup: Setup is complete!
sourceList: click! 
Channel count set to 8
ControlPanel: Found Cyton Dongle on COM port: /dev/ttyUSB0

-------------------------------------------------
ControlPanel: Attempting to Auto-Connect to Cyton
-------------------------------------------------

ControlPanel: Found Cyton Dongle on COM port: /dev/ttyUSB0
Success: Host and Device on Chan using COM port: /dev/ttyUSB0
[DEFAULT]: Attempting to Start Session...
initButtonPressed: Calling initSystem() after next draw()
OpenBCI_GUI: Start session. Calling initSystem().


=================================================
||             INITIALIZING SYSTEM             ||
=================================================

Channel count set to 8
InitSettings: Saving Default Settings to file!
SessionSettings: 3 active widgets saved!
[SUCCESS]: Session started!
New widget [10] selected for container...
Your cursor is in Time Series
Sending config string to board: /2
[DEFAULT]: Starting to read analog inputs on pin marked A5 (D11), A6 (D12) and A7 (D13)
[DEFAULT]: openBCI_GUI: startButton was pressed. Starting data transfer, wait a few seconds.
Brainflow start streaming
[DEFAULT]: Data stream started.
OpenBCI_GUI: openNewLogFile: opened ODF output file: /root/Documents/OpenBCI_GUI/Recordings/OpenBCISession_2021-01-18_16-18-12/OpenBCI-RAW-2021-01-18_16-18-44.txt
New widget [3] selected for container...
Your cursor is in FFT Plot
Networking: Protocol mode set to LSL. Stopping network
Stream update numChan to 8
nPointsPerUpdate 10
dataToSend len: 80
Networking: StringList size=5 [ "Pulse", "obci_eeg1", "PPG", "3", "false" ]
[DEFAULT]: Network Stream Started
[DEFAULT]: Network Stream Stopped
ConsoleLog: Copying console log to clipboard!

[retiutut]

So where did this error come from?

Unexpected error during push_chunk: The number of buffer elements to send is not a multiple of the stream's channel count.

[athanoid]

So where did this error come from?

Unexpected error during push_chunk: The number of buffer elements to send is not a multiple of the stream's channel count.

From the linux console:

[retiutut]

@athanoid I bet I will get the same error if I try on Linux.

Thanks so much for providing information in a timely manner. This means I can start investigating a fix ASAP.

😇

[retiutut]

I was able to replicate this issue on Linux!