Is there a way for the LPC to measure the VBUS voltage via its own ADC?
not sure how the "VBUS_valid" thresholds are measured internally in the chip (or usb phy?)
I found the VBUSVALID_THRESH register, but that doesn't really give me the value of VBUS unless I step through it up and down a few times, not really precise. I'm mainly after being able to read-out a 1-2digit value of what VBUS is at any given time. (ps. boards already fabbed, and no tap from vbus to an adc input pin)
VBUS_valid and USB1_VBUS Threshold input level are the same. Regarding VBUS threshold, it depends on if your device is connected to a high-power or a low-power host. for example, In device mode on LPC55, our device tolerance slightly exceeded USB 2.0 spec. requirement, VBUS_valid is 4.192V.
Thus if USB module detects USB1_VBUS is less than 4.192. USB module can't work normally.
Hope this helps，