USB OTG host in Angstrom

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1

Greetings,

I've been having great success with my new beagle board so far. Thanks
for all the great documentation and information. I have run into one
snag and would like to know if anyone else has seen this problem.

I've installed the Linux Angstrom distribution on a 2G SD/MMC card and
it boots just fine thanks to the great instructions.

I'm trying now to attach a USB mouse and keyboard through a powered
hub and so far have had no luck getting the USB subsystem to recognize
either of these devices. I've tried connecting only one device at a
time without the hub and still get no response.

I've taken care to use the USB mini-A to Standard-A connector
recommended here: http://www.vernier.com/accessories/access.html?usb-mini&template=basic.html

I've also used an ohm meter to make sure pins 4-5 are shorted as
required for a USB OTG host.

When Linux boots, the devices listed under /proc/bus/usb contain
these:

root@beagleboard:/proc/bus/usb# cat devices

T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 3
B: Alloc= 0/800 us ( 0%), #Int= 0, #Iso= 0
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=01 MxPS=64 #Cfgs= 1
P: Vendor=0000 ProdID=0000 Rev= 2.06
S: Manufacturer=Linux 2.6.22.1-omap1 ehci_hcd
S: Product=OMAP-EHCI Host Controller
S: SerialNumber=ehci-omap.0
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=256ms

So it looks like there's an EHCI controller in my system. But no
devices registered on the bus.

I'm guessing that the mini-A connector is wired correctly and the OTG
function of the USB device is working.

I'm now wondering if this is a hardware problem with my Beagle (rev
B4) or possibly the connector is the wrong type for what I'm trying to
do.

Would I have better luck if I connected to the powered hub using a
mini-A to mini-B connector.

Has anyone else had this type of problem?

BTW - I've also tried plugging the Beagle into a PC and it is
recognized as a device under WinXP - seems okay.

Thanks and I look forward to contributing to the project.

Dave

2

When Linux boots, the devices listed under /proc/bus/usb contain
these:
So it looks like there's an EHCI controller in my system. But no
devices registered on the bus.

I think the device listed is the USB controller contained in the OMAP,
not your external host. In general, a USB host incorporates a 1-4
port hub that serves as the root of the USB tree.

An external USB hub is a node in the USB tree. It has a single host
port (usually a female B jack or a short cable with a male A plug)
which must connect to your BeagleBoard USB OTG. The rest of the hub
ports are usually female A jacks into which you plug your USB devices
(mouse, keyboard, etc.). Do not plug your BeagleBoard cable into one
of the hub's device ports. BeagleBoard will only work as a host if
it's connected to the host port. (OTOH, it probably won't do any
damage.)

In my case, I have a hub with a host port cable with a male A plug. I
use a double-female A adapter to connect to my male A to male 5-pin
mini A cable that plugs into BeagleBoard USB OTG.

Also, one way to see if the BeagleBoard software has set it to host
mode is to check the voltage at Pin 1 of the OTG port. R5 is a
convenient place to do it. If the BeagleBoard is in host mode it
drives Pin 1 to 5V (100 mA max). If the BeagleBoard thinks it's a
device, it does not drive Pin 1. (Pin 1 is also 5V if the BeagleBoard
is connected to a hub as a USB device, but in this case it's the hub
that is driving Pin 1 to 5V.)

Hope this helps.