Possibly not a NuttX-specific question.
Short version: how should an App go about determining USB
connect/disconnect (or some higher level USB device status changes that
signifies a successful, perhaps specified-type of connection to a host
PC) in a portable way?
Long version (TL;DR ?): the processor on my board has USBDEV and USBHOST
support that is intended for traditional and separate USB 2.0
connectivity. I have wrapped a USB-C controller (FUSB302) around it so I
can use a single (USB-C) connector as, essentially, an OTG connection.
This works and auto-detects whatever is connected as needing host or
device support and switches everything needed. Works a treat!
The USB-device usage is as a USB composite device (right now), one
element of which is CDC-NCM, the other MSD. This fundamentally works but
I have found that:
* The DHCPD daemon can't be run *before* the first connection to the
host otherwise it stops the CDC-NCM connection being established at
all. It might be a bug in the (example app) daemon but the quick fix
would be to start/stop it on USB connect/disconnect.
* I want to run a (new) mDNS daemon on connection to advertise
services, so I need to know when the USB is connected/disconnected
and the CDC-NCM connection is valid.
So far I have considered:
1. Moving my USB-C/FUSB302 auto switching worker function from being a
board-level function to an app-level function, but it doesn't know
what type of device connection has been made, nor if it was
ultimately successful. Doesn't sound right.
2. USBMONITOR has plenty reporting but it is a bit bewildering, is
intended for DEBUG as I understand it, goes to syslog, and, anyway,
the CDC-NCM code has no useful calls to USBTRACE (although I could
add some.
3. Write my own USBMONITOR task that makes use of the USBTRACE calls
littered throughout the code...if only I could fathom the correct
TRACE value (and then add that to CDC-NCM!). And probably not
portable as it is NuttX-thing?
Since this is *surely* something others have needed to do in the
NuttX/Linux/POSIX world, but my web trawling has so far failed to turn
up anything, I am reaching out as ever to my learned and experienced
e-friends here :-)
Thank you for reading :-)
TimH
