red light after computer wakes up

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metebalci
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red light after computer wakes up

Post by metebalci »

I realized 4424A was not working after computer wakes up, there was a red light on the unit, and PicoScope did not find the unit, however it was visible in Windows 11 device manager. Re-plugging the unit also did not help, I had to restart the PC and then it worked as expected. I thought maybe it is related to USB power down during sleep and disabled the power down on the hub it is connected to. Now after the sleep, PicoScope found it but could not run/use it, the light did not go to green. Re-plugging it worked this time. So my question, is the behavior after sleep defined or should I always re-plug it after sleep or is there a certain setting in Windows that should be used or is it related maybe to some USB controllers ?

Mete

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Re: red light after computer wakes up

Post by metebalci »

I think my question is broader than this. I am also trying to use it with MATLAB and sometimes I see red light and when it appears MATLAB cannot find it, PicoScope 7 also cannot find it. Reconnecting USB does not change, red light stays. I guess the red light is some sort of error signal, but why I cannot reset it ? Is it related to Windows / Windows driver ? I restarted the computer but the red light did not disappear but this time MATLAB found it. So I am very confused what red light signals, and why it happens, and why sometimes programs cannot connect to it but other times can even with red light is on.

metebalci
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Re: red light after computer wakes up

Post by metebalci »

I still experience this issue, after computer woke up from sleep, I found the unit with red light turned on, picoscope could not find it. I have a linux virtual machine running on vmware workstation, I installed picoscope there and connected the unit to virtual machine and it works. Then, I plugged the scope back to Windows and it is not working. It feels like there is an issue with either windows drivers or picoscope windows version, is there a way to debug this ? I tried different USB ports, and tried multiple times unplug/plug and linux is working everytime whereas windows is still not working.

nurber
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Re: red light after computer wakes up

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metebalci
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Re: red light after computer wakes up

Post by metebalci »

I understand it is related to sleep but it is quite strange that it does not recover after replugging, and after the sleep it works with linux but not with windows (11). I disabled USB sleep to check if that helps.

metebalci
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Re: red light after computer wakes up

Post by metebalci »

I disabled USB sleep both in power plan and at the usb root hub at device manager where the picoscope is plugged and it seems to be working OK. I understand the sleep may cause a problem but I think it should recover from that at least by re-plugging (assuming there is no bug in windows or somewhere else in my system).

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Re: red light after computer wakes up

Post by Gerry »

Hi metebalci,

Unfortunately, we only have complete control over our Hardware and Software products, so it's difficult to address issues that relate to hardware and software that our products rely on, such as Operating Systems and Computer Hardware. Sleep mode for Windows O/S is clearly one of these cases, and resuming communication over USB after the computer wakes from Sleep Mode is by no means a simple thing to resolve. There are hidden complexities and when you add to that any nuances that the different Manufacturers of computers can have on the implementation of sleep mode in their products and how the software handles those, you can start to appreciate how difficult this can be to resolve.

In General, PicoScope 7 should now be a bit more robust in recovering from sleep mode, However, where it isn't, currently, there are only 2 options:
[1] You may be able to prevent the PicoScope not responding after waking, by making adjustments to how your computer sleeps (as you have done)
[2] You may have to go through a procedure for reconnecting USB.

So, for the benefit of others who may be experiencing this problem:

Preventing the USB port from sleeping
In Windows you can Disable USB Selective Suspend, which should stop the USB Port from disconnecting the communication. There is some information on how to do this, for the different versions of Windows, here: https://www.startech.com/en-gb/faq/usb- ... sleep-mode.
If that doesn't work then, you can also disable the hub from shutting down by:
1/ In the search box of your toolbar type "co" for Computer Management, then click on "Run as Administrator" in the drop down list.
2/ Select the Device Manager to open it
3/ Go to the menu and select View>'Devices by connection'
4/ Click on the USB Host Controllers to find your PicoScope in the Drop down list
5/ For the USB devices that the PicoScope is listed under (e.g. in the screen shot below,
Finding the hubs used by your PicoScope .png
that includes:
a) Host Controller
b) Root Hub
c) Generic Hub
Right click on them and select Properties
6/ Select the Power Management Tab and deselect "Allow the computer to turn off this device to save power"

Forcing a connection after wake up
If you don't want to, or can't disable the USB port from sleeping then there are some steps you may, unfortunately, need to take to help you to recover from Sleep Mode issues, as follows:
1/ Power-cycle the PicoScope, by disconnecting and then reconnecting the device, which should prompt PicoScope 6 & 7 to search and find your device. Note that if you are using a powered USB hub, then you will probably need to unplug the PicoScope, then power-cycle the hub first, so that the Computer is able to communicate with it, and finally reconnect your device to the hub.
2/ If the PicoScope Software is not resuming then you may need to restart your PicoScope Software.
3/ If after power-cycling, the device is not visible in the Device Manager then you should restart your computer.
4/ If Steps [1], [2] and/or [3] are unsuitable then you may be able to find an alternative machine that works better with your PicoScope during Sleep Mode, or that you can use which doesn't need to be put into a power saving mode.

In the worst case scenario, if none of the above are suitable or effective (e.g. if the Red light on your PicoScope still doesn't clear) then you should contact our Help Desk at support@picotech.com to discuss further help.

Regards,

Gerry
Gerry
Technical Specialist

metebalci
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Re: red light after computer wakes up

Post by metebalci »

Gerry wrote:
Fri Sep 22, 2023 6:34 pm
Hi metebalci,

Unfortunately, we only have complete control over our Hardware and Software products, so it's difficult to address issues that relate to hardware and software that our products rely on, such as Operating Systems and Computer Hardware. Sleep mode for Windows O/S is clearly one of these cases, and resuming communication over USB after the computer wakes from Sleep Mode is by no means a simple thing to resolve. There are hidden complexities and when you add to that any nuances that the different Manufacturers of computers can have on the implementation of sleep mode in their products and how the software handles those, you can start to appreciate how difficult this can be to resolve.
Thanks Gerry for the detailed explanation. I fully understand issues around USB sleep and wake. I find only one case that I experienced (I did not repeat it, so I cannot say this happens always) problematic, which is, after sleep, Windows could not detect the device (after restarting the software, replugging USB etc. nothing helped), however, Linux on the same Windows and hardware but running as a guest inside vmware workstation could detect the device. From this, I derive there was either a problem with Windows, or a non-Picoscope software interacting with Windows, or Picoscope driver. I dont know much about Windows architecture so I cannot say more, and as I said I did not repeat this to see if it is always the case.

I have already disabled USB selective suspend and disallowed sleep on relevant USB controllers and hubs, so I think it is mostly OK for now. In case this is not enough, I also created a task to trigger on workstation lock (because I think a task cannot be triggered before sleep) which kills (taskkill) the picoscope app (picoscope.exe). I think this might also be useful in some unexpected cases. I run picoscope from the last session, so this works fine for me.

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