I am developing a system using LPC54114 and I do not have VBUS connected to any of the IO pins. I'd like USB to be enabled all the time, but the USB core does not enable the D+ pullup until it sees the VBUS signal going high. According to the documentation, the internal VBUS signal should be driven high internally if no signal is routed to VBUS via ICON. (313 in the ref manual: VBUS status input. When this function is not enabled via its corresponding IOCON register, it is
driven HIGH internally.)
However, this does not seem to work. What do I need to setup in the IOCON registers to make sure that VBUS is enabled all the time? The IOCON registers for pin 1-6 and pin 1-11 are both set to func 0 and if I read the VBUSDEBOUNCED bit, it is set to 0.
As soon as I set either of the IOCON registers to mode = 7, the VBUSDEBOUNCED goes high and the usb traffic starts.
How do I enable this without requiring an external signal for VBUS?