USB connector not Mini-AB?

Andy Green andy at
Mon Jul 21 11:44:34 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:
| ma, 2008-07-21 kello 10:24 +0100, Andy Green kirjoitti:
|> We don't monitor ID pin yet to automate this, but we will.
| Funky.
|> You need to provide some magic sysfs poking by hand at the moment to
|> push it between host and device modes.
|> ~  echo host > /sys/devices/platform/s3c2410-ohci/usb_mode
|> ~  echo 1 > /sys/devices/platform/neo1973-pm-host.0/hostmode
| There was some discussion at some point if the Freerunner can be in host
| mode without providing power _while_ charging from outside 5V (for some
| special applications like robotics, obviously with special non-standard
| cabling arrangements), but I don't know if that ended up with an answer.
| Will only changing the usb_mode accomplish this?

Yes, you should set only usb_mode <= host if you give external power
too.  If you set the hostmode guy additionally, it does three things:

~ 1) makes freerunner generate 5V for USB socket to power the device

~ 2) disables charging battery (otherwise we try to charge with the power
we generated from battery :-) )

~ 3) enables 15K pulldowns on USB D+ and D-

When we give external power but want logical host mode, we want 3) but
not 1) and 2).  So the answer is to not set hostmode to "1" in that
case, and add external 15K pulldowns on USB D+ and D-.

Then you have logical host mode that can work with external USB device,
you do not generate 5V for it because you provide it, and you do not
disable charging from this external power you are giving.  This is the
scheme for Joerg's "Y Cable" concept (which somebody actually made with
success I saw the other week).

- -Andy
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Fedora -


More information about the community mailing list