I was wondering if the VBUS signal on the AM1808 could be bypassed, such that the USB interface will still operate without a valid VBUS signal?
It looks like the USBOTGMODE bits in the CFGCHIP2 register may allow for this possibility, however I wanted to confirm it as the user's guide makes it sound like VBUS is needed:
“When assuming the role of a peripheral, assuming that the firmware has set the POWER[SOFTCONN] bit and has enabled the data lines and there is an external host sourcing power on the USB0_VBUS line, the USB2.0 controller will transition to session when it sees power (must be greater or equal to 4.01V) on the USB0_VBUS pin. The USB 2.0 controller will then set the SESSION bit upon detecting the power on the USB0_VBUS line. This will force the USB2.0 controller to sense the state of the USB0_ID pin. If the USB0_ID pin has been left floating, it will know that it has to assume the role of a device and will enable its 1.5 kohm pull-up resistor to signify to the attached external host that it is a Full-Speed device. Note that even when operating as a High-Speed; it has to first come up as Full-Speed. The USB2.0 controller will then await for a reset signal from the host.”
