I am attempting to use the USB OTG and USB Host 1 interfaces on the i.MX6U. The OTG interface connects to a PC and the Host 1 interface connects to a LAN7500 ethernet controller. Out of 10 prototype boards, 2 boards do not recognise the LAN7500 and 1 board does not enumerate on my PC when connected. I've checked all power supplies and soldering connections and haven't found differences between the boards.
I am using at Epson TSX-3225 24Mhz crystal with 12pF capacitors to ground on the input and output pins. I also have a 2.2M resistor from the input to ground. USB_H1_VBUS is supplied with 5V and VDDUSB_CAP is connected to ground through a 2.2uF and 100nF capacitor. The Host 1 USB pair runs directly to the LAN7500 and the OTG diff pair runs directly through a micro USB cable to the PC. Both USB diff traces are impedance matched at 90 Ohms.
I have checked the power requirements on the LAN7500 and have been unable to find any problems there. When I probe the diff pair on a non-functional board the signals stay low.
Has anyone had similar experiences with the USB interfaces or know what I could be doing incorrectly?