Is USB problem supply related ?

Hardware related problems and workarounds

Is USB problem supply related ?

Postby theover » Tue Aug 12, 2014 12:04 am

To check this out a bit, I decided to take the supplied supply unit, put a FET (a BUZ102SL) in between to switch it on and off with, and made a debounced signal to put the FET in on and off mode nearly instantly.

I used a 74HCT00 to make a bi-stable circuit, tapped the +5 Volt from the wall wart to feed it, now I can easily switch the Parallella (a 7010 with connectors) on and off, knowing for sure the FET will supply voltage very fast (and only very little loss about 60mV), and completely de-bounced (no switch artifacts).

Works fine, and I might have a higher probability percentage of functioning USB on my Conrad hub, but: still sometimes the USB didn't start up.

Another problem I've been looking at is that I sometimes got file errors at reboot, on my Parallella supplied sd-card, even though most of the time I filled it with the right OS and files, and it first works fine. I've been pretty neat in using "shutdown -H" and waiting till I was pretty sure the ARMs were in Halt mode to pull the plug out of the wall socket. Yet every now and then, of course after having put a lot of new install stuff on the card (like audio drivers and tools and update Adapteva examples), it creates garbage at startup, too much to find a kernel (FPGA program does continue to work, the LED comes on), and when I take out the card to check in my well working card reader on a Linux system, indeed it says it needs repair. Sometimes FSCHK will repair it, but a couple of times (booting) later, and it ends up having to be rewritten from start. Then it works again.

So I tried if a de-bounced "off" of the board will remedy these occasional file system glitches. Just starting X up, login in, doing a few things, and then killing the power abruptly with the new circuit I made worked without visible error, tomorrow I'll try a few more times with a new "shutdown" to see if the voltage drop of pulling power supply out of the wall socket is the cause of the disk corruption problem.

T.
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Re: Is USB problem supply related ?

Postby ajtravis » Tue Aug 12, 2014 12:51 am

theover wrote:To check this out a bit, I decided to take the supplied supply unit, put a FET (a BUZ102SL) in between to switch it on and off with, and made a debounced signal to put the FET in on and off mode nearly instantly.
[...]
So I tried if a de-bounced "off" of the board will remedy these occasional file system glitches. Just starting X up, login in, doing a few things, and then killing the power abruptly with the new circuit I made worked without visible error, tomorrow I'll try a few more times with a new "shutdown" to see if the voltage drop of pulling power supply out of the wall socket is the cause of the disk corruption problem.

Hi, T.

I've been having problems with USB too and tried setting a bootdelay of 5s thinking that this would allow the power supply to 'settle' before booting Linux. I've also had occasional problems with the SD cards, but thought it was because they were not making contact properly: Re-inserting the cards seemed to fix the problem. The ext4 filesystem uses a journal, which means any uncompleted transactions will be done from the journal when the filesystem is mounted. I've not seen serious filesystem corruption - Just a few orphaned inodes occasionally after a crash.

I've tried the PSU's supplied by Adapteva and a Maplin 8.4A 4-port USB charger, but it made no difference to the reliability of USB being initialised. I find that USB usually works from a cold boot, but if I subsequently reboot or reset then the USB PHY is not detected by the Linux kernel unless I switch the power off and leave it off for more than 15 mins. I'm now wondering if it has something to do with using the UART for serial communications interfering with the USB initialisation because USB seems to be detected more often if I don't use the UART as a serial Linux console.

Hope we can nail this problem down!

Tony.
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Re: Is USB problem supply related ?

Postby ralphmcardell » Thu Aug 14, 2014 5:06 pm

@theover:

Regarding your comments about SD-card file errors at reboot:

I have has similar issues and have had to date to completely re-format and re-create boot and OS images on two of my four Parallella's cards. I also found that sometimes performing a fsck with the partitions mounted on another machine would work, but as you found a few times later the image was so messed up only a format and re-write from scratch would do.

Look forward to you posting more on your findings re: pulling power supply out of wall socket.

Regards

Ralph
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Re: Is USB problem supply related ?

Postby theover » Fri Aug 15, 2014 2:21 pm

I didn't do more than start up and stop a number of times , some with shutdown, some just when Ubuntu wasn't doing much, no SD corruption yet, but that didn't happen too often. In my case, too, besides some unused nodes and so on, the SD card really appeared wrecked somehow, it simply wouldn't even allow the kernel to be loaded properly, and would continue to shoot error messages over the screen.

My USB problem is the "won't start" kind, so the PHY isn't recognized or something, and it can work to simply reset the system at some point, but of course that isn't good for the state of Linux, so that isn't a nice idea. I didn't start sequencing the supply parts (should be possible with the extension board, where some supply enables could be driven buy external sequencing logic), nor did I try some form of reset delay, which probably should be a real fix, combined with possibly a kernel upgrade.

In short most of the times I started with this circuit:

Image

Image

the USB worked, but not exactly every time :(.

T.
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