LPC1787 VBUS pin - self powered

[lpcware]

Content originally posted in LPCWare by SimonThome on Mon Oct 13 07:26:56 MST 2014
I am using the LPC1787 in a self-powered USB device. I am unable to get the LPC1787 to detect the host (and drive the USB_CONN2 pin) when the VBUS pin is driven high from the bus. If I disable VBUS in the IOCON register, then everything works fine. Problem is this is only acceptable for a bus powered application.

Is this a know problem on the 1787?

[lpcware]

Content originally posted in LPCWare by SimonThome on Thu Oct 16 23:40:13 MST 2014
Hi Thanks for the reply, but I am refering to USB Device on a 3rd party proprietary stack

[lpcware]

Content originally posted in LPCWare by terrype on Thu Oct 16 19:45:07 MST 2014
Hi Simon,

I am working with LPC1769 expresso board with LPCOpen2.0., MY usb host msc is working fine but i cannot hot swap the external usb flash.
1. I insert a USB key and LPC1769 epresso board read text file from key
2. I remove the USB key it detect the that usb key is removed but not de_enumerated
3. Insert a new key(or same key) it detect that usb key is inserted but never enumerat
4. It fail to read text file

you may not called usb_enumerate() function

[lpcware]

Content originally posted in LPCWare by SimonThome on Tue Oct 14 00:38:34 MST 2014
It turns out my USB Host stack was disabling the USB_DEV_CLK_EN flag in the USB OTG clock control register, when it was being initialized after the USB Device stack was initialized. This disabled the detection of the presence of the USB bus voltage on the VBUS pin.

The application note "AN11392 - Guidelines for full-speed USB on NXP's LPC microcontrollers" should update the section on ESD diodes and the voltage divider to the VBUS pin.
Consider the following scenario of a self powered USB device:
When the 1K5 pull-up resistor on D+ is enabled, followed by the USB host being disconnected, this will still forward bias the ESD diode between D+ and VBUS. With the suggested resistor divider values of 24K and 39K this will still cause  a logic high to be registered by VBUS, thus the USB controller and stack will not register that the host has actually disconnected from the device.

Can someone at NXP please provide some feedback on this? - Thanks.