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USB Thumb Drive Causing Reboots

GeorgeIoak

I know this has been discussed both here and over on the RPi forums. A lot of talk has gone into the power rails but I haven't seen anyone definitely finding what actually causes the RPi to reboot. I have a "newer" Rev 1 board which has zero ohm resistors at the USB power lines. By adding extra capacitance I can eliminate the reboots but the drive is not always enumerated.

 

Measuring on the scope I can see the 5V rail dip a bit but the 3.3V and 1.8V appear to be stable. I'm powering the RPi through the GPIO header so that would bypass the F1 fuse at the incoming rail.

 

I'm wondering if I'm missing something glitching on the 1.8V rail or is this some type of kernel error causing the reboot? I don't see anything in the log files but I'm also not a Linux guru so maybe I'm not looking in the right places. I did ask this question the other day on the RPi forums but it seems like more engineers hang out here so I'm hoping to eliminate the fluffy comments and opinions.

 

If I missed this somewhere I apologize but hope you'll point me to the right thread.

 

I haven't torn apart a Roku2 but I see that it uses the same LAN9512 and BCM2835 so I'd be curious to see how they did their layout. I can see limiiting the current with the poly fuses but once those are gone and you have a supply with plenty of current and a strong rail I don't see why inserting a drive should cause a reboot. Perhaps this is all related to the problem of the LAN9512 1.8V output tied to the RPi 1.8V rail?

 

Looking forward to hearing what this community has to say!

Parents

  • Hi George,

     

    One way to troubleshoot the problem is connect your thumb drive through a powered USB hub to eliminate the possiblity that you are pulling too much current away from the RPi. The biggest clue is that you are seeing a dip in the 5V rail which can cause the RPi to reboot if it goes below a certain threshold point.even for just a moment.

     

    Mike

  • in reply to msilveus

    This is a known issue on the rev2 board.  It fails to reach USB hotplug standards.

     

    The issue is when you connect the device,It draws too much current...which then causes the raspberry pi to restart.

     

    As Mike said above, the only way to counter the issue is to use a powered hub.

Reply Children
  • in reply to wallarug

    A USB device should not ask for more than 100mA when first attached, only once the host has satisfied itself that the correct configuration file has been read, can the  device request more current.

     

    What happens if the drive is powered externally? - Whoops o course a thumb drive doesn't have external power - that'll teach me not to read fully.

     

    What might happen is that the network data gets priority over the USB data as the netowkr chip is both LAN and USB combined and the chip suddenly uses more power causing a glitch.

     

     

     

    Colin

     

    Message was edited by: Colin Barnard

  • in reply to bodgy

    bodgy wrote:

     

    A USB device should not ask for more than 100mA when first attached...

     

    What might happen is that the network data gets priority over the USB data as the netowkr chip is both LAN and USB combined and the chip suddenly uses more power causing a glitch.

    I think it's most likely good old charge sharing.  When you plug in a USB device with a large discharged 5V capacitor RasPi's capacitors have to provide a big current to make all capacitor voltages equal.  If the USB device's capacitor is too large, the transferred charge causes RasPi's 5V to glitch low.  This didn't happen much on Rev 1 RasPi's since polyfuses F1 and F2 slowed the charging of the plugged-in capacitor.

     

    I saw this many years ago with BeagleBoard rev B4 and wrote up a theory about it.