VBUS required for USB0 on LPC55S16?

[janpieterderuit]

Hi,

I'm trying to make USB0 work as USB device on an LPC55S16.
As we didn't see any note about using VBUS for USB0 in the documantation, we didn't connect it (on P1_11 or P0_22) on our board.

However, I only get USB0 to work when I pull one of those pins high (and the pin should be set to the VBUS function of course).

When I look on the forum, I see some posts about this issue for other LPC families, so I suppose it's the same for LPC55?
Can you please confirm?

As a sidenote:
When I configure P1_11 or P0_22 with USB0_VBUS function, I still get the correct GPIO pin state (high/low) when reading register GPIO->B[port][pin] (using GPIO_PinRead).
Is that intended behavior (which would be beneficial for us), or should we avoid that?

Thanks in advance.

Jan Pieter de Ruiter
Airios

[xiangjun_rong · Accepted solution]

Hi, Jan,

If you use the USB0 module as device mode, You have to connect the USB0_VBUS pin of LPC55S16 to VBUS pin of USB connector so that the USB0 port of LPC55s16 can detect if the USB0 is connected to USB host or not.

The USB0_VBUS is NOT 5V tolerant, so you have to connect the VBUS pin of USB connector to the USB0_VBUS pin(either P0_22 or P1_11) via a resistor divider.

xiangjun_rong_0-1640920041690.png

Regarding your second question, when you configure the P0_22 or P1_11 as USB0_VBUS function via IOCON module, you can read the pin's logic via GPIO input register, you are right. Generally you can read the pin logic via GPIO input register even if you configure the pin as the other peripheral instead of GPIO.

I attach the schematics of LPC55S16-EVK, pls refer to R66/R67 resistor divider.

Hope it can help you

BR

XiangJun Rong