USB remote wake up

merijn · Joined: 06 Jul 2020 Posts: 2

Hi

I'm investigating support for USB remote wake up, but comments in CCS source code mention it is not supported

Ttelmah · Joined: 11 Mar 2010 Posts: 19496

You do understand what this feature actually 'is'?.

This allows the device to wake the PC.

The only devices that normally support it, under Windows currently are
mice, keyboards, network adapters, some USB hubs, and modems.
Basically largely only HID devices.

You need to set the bit in the config descriptor to say that the device
supports this. With this set, when Windows goes to sleep it will send the
USB device a RequestSet packet, saying that it is going to sleep (and
a requestClear when it next wakes). You should toggle a status bit
when these are received, so you know whether the host is awake.

Then when you want to wake the PC (so before doing a data send), you
have to issue a 'resume' on the USB bus. This is done by setting the USB
'K' state for about 10mSec (must be >1, and <15). This depends on your
PIC, but on the USB PIC18's, what you do is set the 'RESUME' bit in
the controller, then clear it 10mSec later.
You should then receive the requestClear packet from the host, when
it wakes.

merijn · Joined: 06 Jul 2020 Posts: 2

Thanks for your reply!

I know enough of this feature to be sure it's what I need in my project, but don't know how to implement it. Since CCS offers libraries for keyboard, mouse and CDC - all device types that support remote wake up - I would have thought it would be implemented in those libraries or somebody on this forum has added support for it and is willing to share.

I'll study the info you gave and hope I can get this implemented. Didn't have much luck with USB in the past, but I'll learn (eventually)

Merijn