> > > > -----Original Message----- > > > From: Marek Vasut [mailto:marex@xxxxxxx] > > > Sent: Sunday, July 07, 2013 9:10 AM > > > To: Chen Peter-B29397 > > > Cc: shawn.guo@xxxxxxxxxx; Michael Grzeschik; maxime.ripard@free- > > > electrons.com; Hector Palacios; linux-usb@xxxxxxxxxxxxxxx; > > > s.hauer@xxxxxxxxxxxxxx; alexander.shishkin@xxxxxxxxxxxxxxx; Estevam > > > Fabio-R49496; Marc Kleine-Budde; m.grzeschik@xxxxxxxxxxxxxx; linux- > arm- > > > kernel@xxxxxxxxxxxxxxxxxxx > > > Subject: Re: Chipidea usb otg support for IMX/MXS (device > functionality) > > > > > > Hi Peter, > > > > > > > > Where can I measure this? > > > > > > > > > > > Two possible reasons: > > > > > > > > > > > > 1. You have not gpio control for vbus toggle when role switches. > > > > > > > > > > This works well. > > > > > > > > > > > 2. Your hardware has some problems that the vbus can't lower > than > > > > > > 0.8v. > > > > > > > > How can I check that? > > > > > > > > Just measure the voltage of your otg vbus pin. > > > > > > It's 2.5 volt for me. What am I supposed to observe happening there? > > > > http://marc.info/?l=linux-usb&m=137242465920952&w=2 > > Dang, must have missed that one, sorry. > > The VBUS is slowly discharging from around 5V to 2.5V , what does that > tell me? > It needs to check your hardware, it is probably there is a high capacitance at vbus pin. Besides, the vbus should be lower than 0.8v if it is disconnected from pc. Best regards, Peter -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
