EV3 freezes without usb connection

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EV3 freezes without usb connection

Postby LastSamurai » Wed Jan 01, 2014 7:24 pm

I have got a strange behaviour here. I use a windows PC + Eclipse and an USB connection to load programms onto the EV3. That (+ running the programs) works. But whenever I disconnect the EV3 it freezes. LCD doesn't change anymore. Buttons still give a "beep" but they don't seem to do anything.
This is kinda annoying, cause I want to try my programm outside of pc range. Do I have to do something before I disconnect them or is this a bug?
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Re: EV3 freezes without usb connection

Postby gloomyandy » Wed Jan 01, 2014 8:42 pm

If the buttons beep then the brick is still running (as is Java), sounds like something in the Menu is hung. Have you tried writing your own program and running that before you disconnect, does your program keep running?
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Re: EV3 freezes without usb connection

Postby lawrie » Wed Jan 01, 2014 9:58 pm

Does it hang consistently every time you disconnect?

If you start the EV3 and immediately connect the PC and then disconnect, does it hang?

If that does not hang, does it always hang after you upload a program (using an ant build file) and then disconnect?

Is there anything else you did before it hung, like use one of the ev3 tools or remote access? Or do you have ssh connected?

As Andy says, it looks like something in the menu program that is not responding for some reason. I have never seen this, but I usually use Wifi rather than USB connections.
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Re: EV3 freezes without usb connection

Postby lawrie » Wed Jan 01, 2014 10:56 pm

This is rather odd. I can make it happen too. The menu starts again when I connect the PC by USB again.

If I also have a Wifi ssh connection, that hangs too, so I cannot run any commands to investigate what is happening.

However, I think I have determined it is not to do with the menu, as if I kill the menu but keep a Wifi ssh connection, that hangs too and starts again, when I reconnect the USB.

Andy, I think it must be something to do with usb networking. It doesn't happen completely consistently. Sometimes when I pull the USB connection out, the Wifi ssh connection just hangs for a while. Sometimes it seems to hang permanently (until the USB is reconnected).

I don't know why the when the menu is running it responds as far as the key beep, but does not display the new screen.
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Re: EV3 freezes without usb connection

Postby gloomyandy » Thu Jan 02, 2014 10:19 am

Hi Lawrie,
strange indeed. It sounds like the USB stuff may be causing some sort of hang in the Network stack (and hence your WiFi connection hanging). Not really sure what we can do about it to be honest as this is all standard Linux code. I guess for now the answer is don't do that.... At some point we might consider switching to the ev3dev kernel and tools, I wonder if that has the same problem. If someone is feeling brave they could check it out. There have been a lot of changes in the area of USB and DMA handling between the Lego/TI kernel and the one used in ev3dev...

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Re: EV3 freezes without usb connection

Postby LastSamurai » Thu Jan 02, 2014 9:35 pm

Strange indeed...
Lawrie got it right. Everthing's the same here. Did some testing too: - if I start the EV3 without USB connection everything works fine. If I start it with the USB connection then the known behaviour starts. Although if I start a programm and then disconnect the USB the programm still executes there is just no more LCD output. So this seems to be a network/lcd problem.
Little annoying for me cause I dont have wifi for my EV3 yet ;)
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Re: EV3 freezes without usb connection

Postby fhbc2003 » Thu Jan 09, 2014 8:22 pm

if I start the EV3 without USB connection everything works fine.

Q: Does this mean you can upload and run new programs as long as you turn on the brick before connecting to USB? Or does the behavior occur whenever you connect the USB? (I want to start working with the EV3 but I need to use USB.)
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Re: EV3 freezes without usb connection

Postby gloomyandy » Thu Jan 09, 2014 9:31 pm

The problem happens when you disconnect the USB after using it as a network connection.
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