USB enumerated sense function

Wizard · Joined: 27 Mar 2006 Posts: 9

Hi there, I'm using a 18F4550 with an USB connection.

I have came to the conclusion that If I don't use the sense pin (100k resistor to ground and 100k to the pin, from the Vbus), the

Ttelmah · Guest

You need the sense pin to do this. Once a device is connected, it _is_ 'enumerated', and this remains true, even if the device is then disconnected. This is normal behaviour for USB devices (even hubs and things respond the same in this regard). 'Enumeration', does not mean that there is a live connection, but that the device has been connected to a system that recognised it, and loaded drivers to support it.
If you don't have a spare pin (which is presumably why you don't want to use connection sense), then consider having the PC driver code send a transfer at regular intervals. Then have a timer on the USB device, which flags an error if a transfer is not received in a reasonable time.

Best Wishes

daveh · Guest

*Solved - see end*
Is there any way to reset the enumeration flag?

I am using a sense pin however that only indicates that 5v is present. If the device is plugged into a powered hub not connected to a computer or a computer when it's starting up/shutting down or a computer that doesn't yet have the driver installed there will be 5v present. Once I sense that the 5v is removed i'd like to reset the usb_enumerated() flag.

I have a red & green LED, Red indicates that the USB is plugged in (sense pin high) and Green indicates a valid connection (sense pin high AND enumerated) both are off if there's no connection.

If I initially plug this in to a powered hub (not connected to computer) it works correctly (red light) however if I plug it into a computer (get the green light) then plug it into the unconnected powered hub I still get green. If I re-issue the usb_init() command it resets ok.

I notice that when I plug this into a computer it goes from red to green, then when I unplug it and re-plug it in it goes Green then red then green. So it appears to be re-enumerating?

Is there a way to reset the usb_enumerated() w/o using the full usb_init()? Or maybe it is best to re-initalize it?

Ok with a little more research I found the answer. With the connection sense pin defined as "USB_CON_SENSE_PIN" I periodically call usb_task().