shut down by software

Any technical questions about the Epiphany chip and Parallella HW Platform.

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shut down by software

Postby paran » Wed Jul 02, 2014 9:32 pm

Hi,
1) Does parallella has a shut down feature (similar to laptops and desktops) that can be shut down and/or reboot by software instead unplugging power cable?
2) How do I communicate with parallella with PC in headless mode? How to connect?
3) Why Ubuntu Linaro was selected for this hardware?
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Re: shut down by software

Postby timpart » Thu Jul 03, 2014 2:47 am

1) sudo shutdown -h now

2) The serial port or over ethernet using ssh

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Re: shut down by software

Postby AlbertoGP » Thu Jul 03, 2014 5:58 am

Does "shutdown -h now" or "halt" turn off the heat-generating components? I guess that would be the FPGA.
More precisely, will the board still overheat if you turn off the fan after stopping it in this way?
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Re: shut down by software

Postby 9600 » Thu Jul 03, 2014 7:37 am

I don't think it does and my guess would be that you still need the fan when the processor is halted.

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Re: shut down by software

Postby tnt » Thu Jul 03, 2014 3:25 pm

You will most likely still need the fan. The board can't really shutdown itself, there is no way for it to cut the power. It will reduce the power a bit of course, but I don't think it will be all that significant. Just before the shutdown you could also deconfigure the fpga ( echo "XXX" > /dev/xdevcfg ) which will shutdown the entire fpga logic and turn off clock to the epiphany. But you'll still have the leakage currents.
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Re: shut down by software

Postby greytery » Thu Jul 03, 2014 4:17 pm

tnt wrote:echo "XXX" > /dev/xdevcfg

Just the sort of thing that should appear in a "Poff" script!

Except that I get "Permission denied", with or without 'sudo'.
(I am running with headless boot).

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Re: shut down by software

Postby FHuettig » Thu Jul 03, 2014 5:20 pm

AlbertoGP wrote:Does "shutdown -h now" or "halt" turn off the heat-generating components? I guess that would be the FPGA.
More precisely, will the board still overheat if you turn off the fan after stopping it in this way?


I just tried this while monitoring the current draw. "sudo shutdown -h now" does not affect the power consumption in any way, so even though the system is "shut down" the ARMs and the FPGA logic all continue to run as normal. It -should- be possible to put the ARMs to sleep but I don't know how. When the board powers-up, for instance, it uses much less power before the image is loaded, but apparently shutdown does not get you back to that state.

greytery wrote:
tnt wrote:echo "XXX" > /dev/xdevcfg

Except that I get "Permission denied", with or without 'sudo'.
(I am running with headless boot).


I'm not a Linux guru, but my impression from running into this problem before is that if you type "sudo echo XXX > /file" the "sudo" only applies to the command and not the redirection, so in that case you are still trying to write to "/file" as your non-root self. If you instead start a root shell by typing "sudo -s" or "sudo su" then you can redirect output to root-owned files. At least it works for me even if I'm not understanding it correctly.

De-configuring the FPGA reduces the power draw to 3W, it will be cooler but probably still needs the fan. Removing the ethernet cable drops another 0.5W. Note that you can deconfigure the FPGA and still talk to the board via ethernet, as long as you don't try to do anything that requires the FPGA resources like talk to the Epiphany.
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Re: shut down by software

Postby FHuettig » Thu Jul 03, 2014 5:22 pm

I can't type "sudo" without thinking of this. :)
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Re: shut down by software

Postby greytery » Thu Jul 03, 2014 5:59 pm

ah! it's same with the command 'make it so' - you've got to have the priviledges of rank!
Forgot that old root/redirection thing - thanks.

The 'shutdown' is a safety command to shut down all 'nix systems for software reasons. I try to remember it always - although I'm not sure just how resilient the latest ext4 file system is to just pulling the plug for those times I forget (at my age ...)
But my close-of-play procedure includes using the same on/off switch to kill the sytem and fan power together.

Looks like there's no hardware answer to the exam question of 'shut down by software' then?
One for Parallella 2.0 Design Specifications perhaps?

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Re: shut down by software

Postby paran » Fri Jul 04, 2014 1:45 am

Hi Everyone,
Thanks to all for participating in this subject. The reason I asked these question is the following:

1) Shutdown by software. -> When I run ubuntu (with hmdi) I've got the common problem like everyone else. When running Firefox, the screen is flashing black. Other browsers do the same. When I tested leaftpad and other applications some will not start, or crash, or hang on desktop screen. This forced me to unplug the unit. Next time I ended up with desktop flashing a black screen. I assumed that ubuntu got corrupted. I think that to prevent this is to do a proper shut down by software before unplugging the power. It does not have to be hardware entirely but just microSD card (for sure) and maybe some other components. On next try I will try to burn the Ubuntu again and try to repeat that and not to do to many things at the same time.
I used separate power for my fan. I cannibalized fan from old PC junk a 12V fan and I used adjustable voltage power adapter for it but both parallella and fan are coming from same cable extension so I am turning both power cables off and on simultaneously.

2) Headless connection - >is it through second usb connector or through 3 pins or ethernet?

3) Why ubuntu linaro -> was it tested before on parallella and it worked before?
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