Irregular timing with 2 g.tec amps
Irregular timing with 2 g.tec amps
Im sorry if this has been addressed before.
I am having irregular timing when I connect two gUSB amplifiers for recording. I don't have this problem when I record with one.
I am using the CursorTask_gUSBamp batch file that came with the distribution, and two gUSBamps connected with a sync cable. I tried uploading the parameter file, but this not allowed? I am recording at 256 sps, 16 channels, 8 on each amp.
Could this be a driver issue? My amps are ~6 years old (not exactly sure if they are version 2, or earlier). I tried following the instructions about drivers on the User Reference:gUSBampADC page http_nospam_www.bci2000.org/wiki/index. ... gUSBampADC. I do have gUSBamp.dll (version 1.0.0.1) in my Windows\system32 folder, but no such driver in by BCI2000/prog directory.
Thanks in advance,
Andrew
I am having irregular timing when I connect two gUSB amplifiers for recording. I don't have this problem when I record with one.
I am using the CursorTask_gUSBamp batch file that came with the distribution, and two gUSBamps connected with a sync cable. I tried uploading the parameter file, but this not allowed? I am recording at 256 sps, 16 channels, 8 on each amp.
Could this be a driver issue? My amps are ~6 years old (not exactly sure if they are version 2, or earlier). I tried following the instructions about drivers on the User Reference:gUSBampADC page http_nospam_www.bci2000.org/wiki/index. ... gUSBampADC. I do have gUSBamp.dll (version 1.0.0.1) in my Windows\system32 folder, but no such driver in by BCI2000/prog directory.
Thanks in advance,
Andrew
Re: Irregular timing with 2 g.tec amps
Andrew,
I would suggest to contact g.tec to get a new driver. Yours appears to be ancient.
Gerv
I would suggest to contact g.tec to get a new driver. Yours appears to be ancient.
Gerv
Re: Irregular timing with 2 g.tec amps
I've updated both the drivers and firmware for my amps.
From the gUSBamp demo application:
SNR=UA-2006.10.05
HWVER=V2.0
VER=2.0.2
SNR=UA-2006.10.06
HWVER=V2.0
VER=2.0.2
In device manager, I can see that both are using driver version 3.4.1.20
With both amps connected, I get block time irregularities every 5 seconds or so. (This is an improvement compared to nearly continuous block irregularities) When I ran CursorTask with 1 amp, I saw no timing irregularities
From the gUSBamp demo application:
SNR=UA-2006.10.05
HWVER=V2.0
VER=2.0.2
SNR=UA-2006.10.06
HWVER=V2.0
VER=2.0.2
In device manager, I can see that both are using driver version 3.4.1.20
With both amps connected, I get block time irregularities every 5 seconds or so. (This is an improvement compared to nearly continuous block irregularities) When I ran CursorTask with 1 amp, I saw no timing irregularities
Re: Irregular timing with 2 g.tec amps
Which BCI2000 version are you using?
Gerv
Gerv
Re: Irregular timing with 2 g.tec amps
What happens when you use the TaskManager to set the CPU Priority of the Source module to Real Time?
Gerv
Gerv
Re: Irregular timing with 2 g.tec amps
While CursorTask was running, I changed the priority on the gUSBampSource process from Realtime to Normal to Low.
Realtime: Normal: Low: It makes sense that the stimulus duration becomes more erratic when I devote more CPU to the source module, but I see no differences in the block irregularities.
Realtime: Normal: Low: It makes sense that the stimulus duration becomes more erratic when I devote more CPU to the source module, but I see no differences in the block irregularities.
Re: Irregular timing with 2 g.tec amps
A few more ideas.
#1: I understand you do 256 Hz. What is the SampleBlockSize?
#2: Does anything change if you go to 16 channels on each amp (32 total)?
#3: How did you connect the g.USBamps? If you use a USB splitter, or even otherwise, they may be on the same USB controller, and what you see may be an issue with that controller. You could try to put the two amps on two separate controllers (e.g., connect one to the front of the computer, and one to the back).
Gerv
#1: I understand you do 256 Hz. What is the SampleBlockSize?
#2: Does anything change if you go to 16 channels on each amp (32 total)?
#3: How did you connect the g.USBamps? If you use a USB splitter, or even otherwise, they may be on the same USB controller, and what you see may be an issue with that controller. You could try to put the two amps on two separate controllers (e.g., connect one to the front of the computer, and one to the back).
Gerv
Re: Irregular timing with 2 g.tec amps
1) My sample block size is 8
2) Changed both amps to record 16 channels each. No change.
3) I connect my amps with the sync cable, and plug each of their usb cables into a port on my laptop. I tried plugging one into a port on the opposite side of the laptop, but there was no change.
2) Changed both amps to record 16 channels each. No change.
3) I connect my amps with the sync cable, and plug each of their usb cables into a port on my laptop. I tried plugging one into a port on the opposite side of the laptop, but there was no change.
Re: Irregular timing with 2 g.tec amps
I think I am running out of possible reasons for this. We definitely know of (even much more demanding) configurations that do not show these irregularities. The only thing I can still think of is to try a different computer, or to see if you can increase the polling cycle of the USB controller and/or decrease the time slice of the Windows scheduler.
What I do know is that these timing irregularities do not happen often and are quite small (half a Sample Block=16 ms). You will also not lose any data. Thus, this will only be of concern for a very small fraction of applications. The effect on typical mu-rhythm or P300 experiments should be negligible.
Gerv
What I do know is that these timing irregularities do not happen often and are quite small (half a Sample Block=16 ms). You will also not lose any data. Thus, this will only be of concern for a very small fraction of applications. The effect on typical mu-rhythm or P300 experiments should be negligible.
Gerv
Re: Irregular timing with 2 g.tec amps
Thank you for your help Gerv,
I agree with your second point. I haven't seen any data loss with these irregularities. How exactly might periodic 16 ms delays affect a P300 task? My guess is not much because the P300 signal is broader than this.
Andrew
I agree with your second point. I haven't seen any data loss with these irregularities. How exactly might periodic 16 ms delays affect a P300 task? My guess is not much because the P300 signal is broader than this.
Andrew
Re: Irregular timing with 2 g.tec amps
I do not think that a sporadic 16 ms jitter will affect the P300 system very much. We have been very successful with P300 experiments with wireless EEG devices that typically have quite poor timing performance.
Gerv
Gerv
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