Difference between revisions of "Category:How to - usb"

Revision as of 11:48, 5 December 2009

USBNet with Overo

The OTG USB port on the Overo expansion boards can be configured to support USB networking. To enable this, the OTG port needs to be configured as a USB peripheral or gadget. The default kernels from Gumstix have the OTG port configured to act as a USB host.

The procedure for changing the configuration requires rebuilding your kernel, so you should first be comfortable with setting up a build environment and building images for your Overo.

The steps below assume a recent snapshot of the gumstix-oe git tree. Two recent changes in particular have simplified the process.

1. Kernel 2.6.31 is now the default

2. The linux-omap3_2.6.31.bb recipe now has variable whose value results in modifying the defconfig file appropriately.

To get started, first edit the recipe file ${OVEROTOP}/org.openembedded.dev/recipes/linux/linux-omap3_2.6.31.bb

Change the line

MUSB_MODE ?= "host"

to

MUSB_MODE ?= "peripheral"  

or "otg".

Next rebuild the kernel and rootfs.

cd ${OVEROTOP}
bitbake -c clean linux-omap3-2.6.31
bitbake -c rebuild linux-omap3-2.6.31

And then rebuild your image.

bitbake omap3-console-image    

Change omap3-console-image to whatever image you use.

Once you have booted the new system, you still need to load the g_ether driver since it was built as a module.

You can add g_ether to /etc/modules if you always want it loaded at boot.

root@overo# modbprobe g_ether
g_ether gadget: using random self ethernet address
g_ether gadget: using random host ethernet address
usb0: MAC d6:2c:8f:d9:51:32
usb0: HOST MAC f2:99:dc:4c:cb:7a
g_ether gadget: Ethernet Gadget, version: Memorial Day 2008
g_ether gadget: g_ether ready

root@overo:~# ifconfig -a
lo      Link encap:Local Loopback
        inet addr:127.0.0.1  Mask:255.0.0.0
        inet6 addr: ::1/128 Scope:Host
        UP LOOPBACK RUNNING  MTU:16436  Metric:1
        RX packets:0 errors:0 dropped:0 overruns:0 frame:0
        TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:0
        RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

usb0    Link encap:Ethernet  HWaddr D6:2C:8F:D9:51:32
        BROADCAST MULTICAST  MTU:1500  Metric:1
        RX packets:0 errors:0 dropped:0 overruns:0 frame:0
        TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:1000
        RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

Configure the usb0 interface the way you would any other.

For example

root@overo:~# ifconfig usb0 192.168.20.2 netmask 255.255.255.0

If you then plug the usb OTG cable into a host computer ready for usb networking you'll get a console message

g_ether gadget: high speed config #1: CDC Ethernet (ECM)

The rest is all standard Linux networking.