LPC54114 without VBUS connected to 1-6 or 1-11

[stefanburstrom]

Hi!

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?

best regards,

Stefan

[Dezheng_Tang]

You do need to configure P1.6 as VBUS in order for USB to work.

Inside the USB IP, once this pin is configured as VBUS, it controls the pull-up on D+ line internally once DCON bit (bit 16) in DEVCMDSTAT register is set to 1. In IOCON, by default, all the pins are pulled up internally including p1.6, so, even if you disconnect the USB cable, you may not see the connect change in the status register. You need to set

to the mode bits to inactive once you configure this p1.6 as VBUS in IOCON.

In short, even if you want USB enabled all the time, you need to configure P1.6 as VBUS and can't use this pin for some other purposes.