LPC Microcontrollers中的主题 Re: Measure USB1_VBUS via internal ADC?

Measure USB1_VBUS via internal ADC?

dav1 — Mon, 08 Aug 2022 16:11:04 GMT

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)

Re: Measure USB1_VBUS via internal ADC?

ZhangJennie — Fri, 12 Aug 2022 09:02:44 GMT

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，

Jun Zhang