Configure USB power for a webcam



I am trying to plug in a USB webcam to record photos or video.
I have installed fswebcam to take a test picture, but it is not working.
I believe the problem is that the USB port is not able to supply enough power for the webcam.

  1. Trying to take the picture, there is no recognized camera in /dev/video0:
pi@autopi-:~ $ fswebcam test_pic.jpg
--- Opening /dev/video0...
stat: No such file or directory
  1. When the camera is plugged:
pi@autopi:~ $ lsusb -v | egrep "^Bus|MaxPower"
Bus 001 Device 006: ID 046d:081b Webcam
    MaxPower              500mA
  1. Trying to find about the power of the USB ports (this one should be it since the id matches):
pi@autopi:~ $ usb-devices
T:  Bus=01 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#=  6 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=046d ProdID=081b Rev=00.10
S:  SerialNumber=F5908A20
C:  #Ifs= 0 Cfg#= 0 Atr= MxPwr=

There doesn’t seem to be a fixed MxPwr value.

  1. In fact, after plugging the webcam:
pi@autopi:~ $ dmesg
[  120.973410] usb 1-1.1: new high-speed USB device number 6 using dwc_otg
[  121.314925] usb 1-1.1: New USB device found, idVendor=046d, idProduct=081b
[  121.314950] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=2
[  121.314963] usb 1-1.1: SerialNumber: F5908A20
[  121.315687] usb 1-1.1: rejected 1 configuration due to insufficient available bus power
[  121.315710] usb 1-1.1: no configuration chosen from 1 choice
[  121.315721] usb 1-1.1: No support over 100mA
[  121.315985] usb 1-1-port3: 500mA is over 100mA budget!
[  121.316004] hub 1-1:1.0: 150mA over power budget!

So my question is, how can I get around this?
Is there a way to increase this threshold?
Since the USB ports are not in the Pi Zero (but in the autopi board) maybe you could help.

Thanks in advance,

Raspberry Pi 3B+ with AutoPI 4G/LTE Power Issue[SOLVED]

Hi Iker,

You can override the power safety by altering the udev rules:

echo 1 > /sys/bus/usb/devices/1-1.4/bConfigurationValue

Replace “1-1.4” with your USB device ID.

Please notice, you need some kind of script to persist this after a reboot.



Hi @Peter,

Thanks a lot for the prompt reply.
I did cat /sys/bus/usb/devices/1-1.1/bConfigurationValue first.
I obtained a 1, and later it started working.
Not sure of what happened but now it works every time (even after reboot :man_shrugging:).

Thanks for the support.


Hi iipr,

I’m also playing around to get a USB camera working. I actually got one myself.
You stated that you installated fswebcam on the autopi. Did you install it by simply running “sudo apt-get install fswebcam” ? If not, what syntax did you use?

Your help would be much appreciated…

Best regards,


Hi @Pravin,

Yes, that’s what I did. Here there is some more information.

Depending on what you want to do, it may be useful to try OpenCV directly from Python.