From mboxrd@z Thu Jan 1 00:00:00 1970 From: marex@denx.de (Marek Vasut) Date: Fri, 28 Jun 2013 13:56:51 +0200 Subject: Chipidea usb otg support for IMX/MXS (device functionality) In-Reply-To: References: <51A5A808.2070803@digi.com> <201306281142.51676.marex@denx.de> Message-ID: <201306281356.51670.marex@denx.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Dear Chen Peter-B29397, > > 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. Ok, I see it's 2.25 volts after I disconnect the microB-A thing . I should see 0.8V constantly with nothing connected on the port? Best regards, Marek Vasut