ubuntu-phone team mailing list archive

["Stephen M. Webb" <stephen.webb@xxxxxxxxxxxxx>]

On 15-09-12 08:11 AM, Ed Kapitein wrote:
> Hi,
> i want to use a raspberry pi to charge the BQ 4.5, without a (powered) hub.
> The BQ is not charging when i plug it into the pi, and the pi never enumerates the BQ on its usb bus.

Sounds like they're both OTG connections, each waiting for the other to assert host mode.

It's possible neither device has a kernel that supports host mode on the OTG port:  you can check on the devices using
the command line 'grep CONFIG_USB_OTG /boot/config-$(uname -r)'.  In particular, this is required on the Pi, which has a
USB Standard-A connector so needs to play the host.

It's also very possible you're using a regular USB cable and not an OTG cable, so host-slave nego never happens and
they're both waiting in slave mode for the other device to assert dominance through hardware signalling.  See the
Wikipedia entry https://en.wikipedia.org/wiki/USB_On-The-Go for a detailed description.

--
Stephen M. Webb  <stephen.webb@xxxxxxxxxxxxx>