Aquisition problem - Problem with the USB port

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25 Jan 2012
Posts: 3

Hello everyone,

I'm using a CS328A (serial number > 4000) via USB on a WinXP machine with the standalone cleverscope software.
Everything worked great some weeks ago, but when I tried to scope something again yesterday, I was suddenly confronted with those problems:
- When starting a continuous capture ("Auto" button), it needs about 2 seconds until I see the first frame. Before, it started nearly instantaneous.
- In most cases, aquisition won't work at all (whether triggered or not doesn't matter). The button looks active, but nothing happens. Sometimes, an error message will occur, telling me that there is a problem with the USB port, sometimes not. Sometimes, aquisition will start after several tries and wait times, sometimes not.

I haven't changed anything regarding the scope drivers or application, so this behaviour was strange enough. But then, I tried
- changing the USB port
- changing aquisition/trigger/program/view settings in every way
- updating the cleverscope software to the newest version
- uninstalling and reinstalling VISA driver and application
and still, the problem remains.

Does someone have a clue how and why this happens, and how to get the scope to working properly again? I can't work with a scope that will aquire only sporadically...

31 Jan 2012
Posts: 399

Dear Lord,
Our first guess is that you have an interfering USB device that is hogging bandwidth. An example is the PicKit device. Try unplugging other USB devices and seeing if anything changes. Have you recently acquired a new device? We would not expect the Cleverscope app to behave the way you are describing!

31 Jan 2012
Posts: 3

Dear bartschroder,
Thanks for your response!
I have tried your suggestion to remove all other USB devices (of which no one should normally have high bandwidth usage), but there was no change of the problem.
My device is the same I have already used before; it is not new.

But now I noticed a regularity of the behaviour:
Always exactly 10 seconds after I have turned off the aquisition, Windows seems to disconnect and reconnect the device as I hear the typical sounds for that. Only after this strange automatic reconnect, I'm able to start a new aquisition. Once it is started, it can last forever without any problems. Starting aquisition during these 10 seconds results in the behaviour I described in the first post: an activated button, but no data update.
So maybe it is a Windows problem? But I can't think of any reason why Windows would want to cut and reestablish the USB connection always 10 seconds after an aquisition has been stopped...?
Oh, besides: The error message "problem with the USB port" occurs only when I try to start the aquisition during the time of the reconnect (about 1 to 2 seconds long).
Did you ever hear of something like this?

10 Feb 2012
Posts: 399

Dear Lord,
we have been trying to get to the bottom of this problem. We have not been able to reproduce it under USB. Interestingly, we can reproduce exactly the problem you are seeing when using an Ethernet connection, and this sequence:
1. Start up acuisition unit.
2. Start program, and acquire something. First acquisition happens correctly.
3. Leaving the acquisition unit connected, and powered up, exit the program, and then start it again. Click Auto as soon as it starts. If the time from close down to Auto is less than 10 seconds, we getthe USB disconnected message (the next version of the application correctly identifies the failoed connection). After a failure, if we wait more than 10 seconds, the acquisition unit starts correcty.

After some research, we discovered this was caused by the Windows (and Bit Defender does it as well) Firewall. It stops rapid disconnection and reconnection. Disabling the Firewall made the problem go away. This is apparently an anti-virus activity.

You are using USB, which is different. All the same, you might like disabling your firewall, just to check it out.

8 Mar 2012
Posts: 3

Dear bartschroder,
I have tried to deactivate firewall and anti-virus software, but nothing changed. But I'm used to this behavior now, so I can work with it quite comfortably.
Thanks to you and your team for putting such an effort into this!
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