Hello,
I am not the world's biggest USB expert, thus I am a little puzzled about the LPC2478 needing to handle USB interrupts regularly even when not connected to a host (without the USB cable connected, even). I am running a CDC connection. Is there a good explanation for this or do I need to disable the ISR until I see USB Vcc appearing?
> the LPC2478 needing to handle USB interrupts regularly even when not connected to a host
Usually, you don't see any USB interrupt while disconnection. It may be caused by noise on the D+/D- pins.
For self-powered device,
- Disable USB engine while disconnection (PCUSB bit of PCONP). Initialize it after the detection of VBUS voltage
OR
- Attach extra pull-ups (100k or more) to the D+ and D- pins, if the USB engine is kept alive.
Tsuneo
Thanks, Tsuneo. Will do.