Why you a talking about only voltage? One of the difference between OTG aned HOST is max amperage. For OTG you can use up to 100 mA, but for HOST up to 500 mA (the maximum allowed according to USB standards), both have 5 V between 1 & 4 pins.


On Wed, Apr 18, 2012 at 4:11 PM, Lou Morda <lmorda81@gmail.com> wrote:
Hey guys,

Jack and Don suggest that I keep posting on here... hopefully someone can answer.

I've got an overo connected thru a stagecoach.  I'm connecting a usb peripheral to the usb otg port of the stagecoach.  The usb device is a radio.  Sometimes the gumstix connects with the radio, and other times it does not.

I've learned the following in the last couple of days.  First, other people are having problems with the USB OTG port.


Second, the radio I have needs a 5V signal to let it know that a USB connection is present, and it does NOT draw any current.  So, it seems that sometimes the gumstix sends the required 5V, and sometimes it does not.  Third, according to the above post, I'm not using the correct cable.  I've got a Standard A USB 2.0 cable coming from the radio, and I've connected that to the USB OTG port with a mini B adapter. Fourth, the connection works every single time if I put a powered usb hub in between the USB OTG and the raido.

Two questions:

Do i HAVE to use a powered usb hub?  I'm pretty sure if I do that may kill my project.

If I use the USB mini B to mini A cable on the gumstix website (and also talked about in the above mailing list post), will that "work every time" without a powered usb hub?  Like, if I use that cable, then will the gumtsix know that it is a usb host "every time", and send the required 5V signal to the radio?


-Louis Morda
 SAIC Computer Scientist

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