I have a PCB with a PowerPC 85xx (Freescale QorIQ P1020) MCU and an ISP1507B USB ULPI PHY that is supposed to act as a host controller.

On the board, the USB_POWERFAULT input on the MCU and the FAULT input on the ISP1507 are connected to a comparator that is active high whenever VBUS is missing (it thus comes out of reset with this pin active). The VBUS pin on the ISP1507 is connected through a 1k resistor to the VBUS pin on the USB connector, enabling it to sense the voltage. An external voltage switch that is controlled by (activated with low level) PSW_N on the ISP1507 supplies 5V current to the USB connector.

My problem is that U-BOOT does not turn on the VBUS voltage using it's PSW_N pin when I run the command "usb reset". If I however force-feed the USB connector with 5V using a battery, "usb reset" finds my mass storage device in the connector.

Is there any easy way of getting U-BOOT to handle the FAULT- and PSW_N-pins they way I need them to?

Best Regards Daniel Nilsson