Since nobody has responded yet I'll try to provide a little help. Which USB devices do you have?
You can use
-d N to select specific devices you
want to use, where N is the device number. You should be able to see the device numbers by running bfgminer with the
-n argument (open a command window, navigate to bfgminer's folder, type
bfgminer.exe -n, press Enter. It will list devices and exit so you need to have the command window open first... otherwise it will just close before you can read it.)
I found cgminer's options for enabling/disabling specific devices to be easier (better). There are three methods you can use for selecting which USB devices to run or not run. But switching to cgminer means you have to uninstall the USB to UART drivers and use Zadig to install the WinUSB drivers. You'd then have to also switch to using cgminer for the USB devices, assuming you'll be running another instance for them.
From the cgminer readme on enabling/disabling USB devices:
The --usb option can restrict how many Avalon, BFL ASIC, BitForce FPGAs,
Klondike ASIC, ModMiner FPGAs or Icarus bitstream FPGAs it finds:
--usb 1:2,1:3,1:4,1:*
or
--usb BAS:1,BFL:1,MMQ:0,ICA:0,KLN:0
or
--usb :10
You can only use one of the above 3
The first version
--usb 1:2,1:3,1:4,1:*
allows you to select which devices to mine on with a list of USB
bus_number:device_address
All other USB devices will be ignored
Hotplug will also only look at the devices matching the list specified and
find nothing new if they are all in use
You can specify just the USB bus_number to find all devices like 1:*
which means any devices on USB bus_number 1
This is useful if you unplug a device then plug it back in the same port,
it usually reappears with the same bus_number but a different device_address
You can see the list of all USB devices on linux with 'sudo lsusb'
Cgminer will list the recognised USB devices with the '-n' option or the
'--usb-dump 0' option
The '--usb-dump N' option with a value of N greater than 0 will dump a lot
of details about each recognised USB device
If you wish to see all USB devices, include the --usb-list-all option
The second version
--usb BAS:1,BFL:1,MMQ:0,ICA:0,KLN:0
allows you to specify how many devices to choose based on each device
driver cgminer has - there are currently 5 USB drivers: BAS, BFL, MMQ.
ICA & KLN
N.B. you can only specify which device driver to limit, not the type of
each device, e.g. with BAS:n you can limit how many BFL ASIC devices will
be checked, but you cannot limit the number of each type of BFL ASIC
Also note that the MMQ count is the number of MMQ backplanes you have
not the number of MMQ FPGAs
The third version
--usb :10
means only use a maximum of 10 devices of any supported USB devices
Once cgminer has 10 devices it will not configure any more and hotplug will
not scan for any more
If one of the 10 devices stops working, hotplug - if enabled, as is default
- will scan normally again until it has 10 devices
--usb :0 will disable all USB I/O other than to initialise libusb
NOTE: The --device option will limit which devices are in use based on their
numbering order of the total devices, so if you hotplug USB devices regularly,
it will not reliably be the same devices.
On a somewhat related note: If you're mining scrypt coins it should only use GPUs automatically.
