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I have a rather strange problem. If I boot my Pi with only power, HDMI & and ethernet cable plugged in, the ethernet port and other USB devices will flash on (i.e. the ethernet lights and LEDs on my USB wifi dongle) then off and cycle. I don't believe that too much current is being drawn from the power supply (I've tried 1A & 2A) as I've used the Pi in this configuration before and it also doesn't work with no USB devices plugged in.

However, when I plug in my Corsair K70 to the Pi (it has 1 USB port for the keyboard and one for power - it has lights), I think it powers the other USB devices as the ethernet and wifi dongle work. Also, when attempting a reboot, I noticed that when the (micro USB) power cable is unplugged from the Pi, the Corsair USB can keep the Pi powered on (I think there might be a kernel panic).

I have looked at dmesg but all it shows is the devices being found then disconnecting.

[ 1072.100878] usb 1-1.2: USB disconnect, device number 66 // Keyboard being unplugged
[ 1073.644513] ERROR::dwc_otg_hcd_urb_enqueue:505: Not connected    


[ 1073.738090] usb 1-1: USB disconnect, device number 64
[ 1073.738134] usb 1-1.1: USB disconnect, device number 65
[ 1073.738530] smsc95xx 1-1.1:1.0 eth0: unregister 'smsc95xx' usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet
[ 1073.738632] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
[ 1073.928122] Indeed it is in host mode hprt0 = 00021501
[ 1074.167959] usb 1-1: new high-speed USB device number 68 using dwc_otg
[ 1074.168253] Indeed it is in host mode hprt0 = 00001101
[ 1074.438519] usb 1-1: New USB device found, idVendor=0424, idProduct=9512
[ 1074.438561] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 1074.454142] hub 1-1:1.0: USB hub found
[ 1074.454347] hub 1-1:1.0: 3 ports detected
[ 1074.737987] usb 1-1.1: new high-speed USB device number 69 using dwc_otg
[ 1074.838538] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
[ 1074.838580] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 1074.847715] smsc95xx v1.0.4
[ 1074.929361] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:19:5a:3a
[ 1076.481477] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
[ 1076.482688] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 1077.488139] usb 1-1: USB disconnect, device number 68
[ 1077.488179] usb 1-1.1: USB disconnect, device number 69

Then when I plug the keyboard back in:

 [ 1083.668000] usb 1-1: new high-speed USB device number 72 using dwc_otg
 [ 1083.668304] Indeed it is in host mode hprt0 = 00001101
 [ 1083.938485] usb 1-1: New USB device found, idVendor=0424, idProduct=9512
 [ 1083.938527] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
 [ 1083.954005] hub 1-1:1.0: USB hub found
 [ 1083.954225] hub 1-1:1.0: 3 ports detected
 [ 1084.237986] usb 1-1.1: new high-speed USB device number 73 using dwc_otg
 [ 1084.338525] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
 [ 1084.338540] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
 [ 1084.350547] smsc95xx v1.0.4
 [ 1084.449214] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:19:5a:3a
 [ 1085.971500] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
 [ 1085.972762] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
 [ 1087.467867] usb 1-1.2: new full-speed USB device number 74 using dwc_otg
 [ 1087.575897] usb 1-1.2: New USB device found, idVendor=1b1c, idProduct=1b13
 [ 1087.575938] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
 [ 1087.575961] usb 1-1.2: Product: Corsair K70 RGB Gaming Keyboard 
 [ 1087.575981] usb 1-1.2: Manufacturer: Corsair
 [ 1087.575998] usb 1-1.2: SerialNumber: 1204302DAE3B9407536FEC40F5001946
 [ 1087.607092] input: Corsair Corsair K70 RGB Gaming Keyboard  as /devices/platform/soc/20980000.usb/usb1/1-1/1-1.2/1-1.2:1.0/0003:1B1C:1B13.0005/input/input4
 [ 1087.659626] hid-generic 0003:1B1C:1B13.0005: input,hidraw0: USB HID v1.11 Keyboard [Corsair Corsair K70 RGB Gaming Keyboard ] on usb-20980000.usb-1.2/input0
 [ 1088.408346] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0xC1E1
 [ 1088.412633] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready

Should I give up on this Pi? (At least for anything that needs USB/ethernet) Have I destroyed some power supply component or is there hope yet?

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2 Answers 2

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This was a power supply problem. If you get something like this, check that enough power is being supplied to the Pi e.g. with a multimeter; or if you haven't got one, try a different supply and cable.

A faulty cable meant that the Pi was not receiving enough/stable enough power and was unable to power the USB.

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It is possible to backpower the Pi through the USB but I am pretty sure doing this and providing power via another means is probably a bad idea -- as in one which may lead to damage. If that Corsair keyboard is backpowering this way, it may be defective, since that is definitely not something that is a good idea to do to a normal computer (plug a voltage source into the USB jacks).

The fact that you can unplug the Pi and have it remain on obviously means it is providing power. Looking at the product description, I don't see any indication that it has some kind of circuitry to play such a role properly; it's also not clear exactly what that "extra power" jack you refer to is. My guess would be that it was meant to be used either with both plugs attached to the same computer (which would be okay; this allows it to get more than 500 mA from a USB 2.0 hub), or else you've confused the "pass through" connector, intended to provide a device jack on the keyboard (i.e., an input), for a second output jack, and because it is wired to the real output, attaching that to a power supply affects the whole circuit.

Whoops.

Either way, powering that from one place then attaching it as a device to another is, again, a bad idea. It may already have permanently damaged the Pi -- don't do it again with anything else.

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  • Thanks, just wanted to confirm that it was probably dead. Lesson learnt :P
    – Kian
    Commented Sep 23, 2016 at 20:06
  • Kian: Someone may come along with better knowledge of exactly how that could happen -- I'd just guess the 5V regulator is damaged and can't properly provide the ethernet/USB controller (it is all one chip) anymore. Note that if you are lucky, it could be polyfuse related; try leaving it unplugged for a few days and see if it is okay after that. @Ghanima So no cake for you then.
    – goldilocks ♦
    Commented Sep 23, 2016 at 20:12
  • Turns out it was just a faulty power cable! Only discovered after I had problems with a brand new Pi 🤦
    – Kian
    Commented Sep 26, 2016 at 12:12
  • I still would not plug that keyboard in using a separate power supply unless you have documentation for it that says that is okay, because if it was back-powering a pi in the way you describe I am sure it was not intended to be used that way. +/2/3 models can put out 1 A+ over the USB if you set max_usb_current (see raspberrypi.stackexchange.com/q/46437/5538), so if you want to plug both lines from the keyboard into the pi do so, but don't put one into the pi and one into a wall wart.
    – goldilocks ♦
    Commented Sep 26, 2016 at 12:18
  • I don't plan to after that scare! Thanks for the tips!
    – Kian
    Commented Sep 26, 2016 at 12:46

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