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USB driver in WEC7 BSP for AM3874

Michi Yama
Guru 10030 points
Other Parts Discussed in Thread: AM3874

Hi,

I would like to know the behavior of the USB OTG module for AM3874.

My customer uses USB OTG module of AM3874 as host. For this reason, they connect USBx_ID pin to Ground. This means AM3874 USB roles as A device (host).

But, in this setting, bit 7 of Device control register changes frequently. Please see the below figure.

I know IDDIG bit of USB Mode register will override the ID sense value and force the controller to operate as the USB Host or a USB Device.

So the OTG module can be changed even though USB_ID pin is set as host.

But  I don't  know why USB module changes the role A device - B device frequently. Is this behavior normal action by USB driver?

Also my customer says, AM3874 OTG module always become to be as B device when the USB memory is inserted to AM3874 system. And after that, OTG module become to be as A device(host) even though USB_ID pin is always pulled down.  Is this behavior also by  USB driver?

Please let  me know.

Best regards,

Michi