On 2011-02-14 10:14, Geo wrote: > Joe Koberg wrote: > I have tried using the $80 and $81 USB keyboard codes from an AVR HID > device but they are ignored by my windows XP PC. > My Dell Latitude laptop has Fn volume control keys but according to the > utility (mentioned below) they use reserved scan codes (presumably a > specific keyboard driver required). > This utility for viewing USB keycodes on the PC helped to discover that > windows was not dealing with the keyboard codes:- > > > I can change the windows volume control from the USB port by identifying > the hardware as a "Consumer Device" and using the report descriptor from > this page:- > > As he uses a PIC and encoder it may be useful to you. > Changing the volume control via USB /does/ reset the screensaver timeout. > Yes, after doing some reading it looks like the consumer device usage=20 page is the way to go... In fact I think I read that the keyboard usage=20 bytes are signed chars, so no values over 0x7F are accepted by Windows. However now I have to go poke around in the JALlib usb libraries and=20 learn how to define/use the different descriptor. Too bad, the previous=20 attempt was so dang easy with less than 30 lines of code! I guess I=20 will have a chance to submit a usb_consumer.jal to the JALlib project=20 along with my new arbitrary-precision fixed-point arithmetic library.... Thank you very much for your on-topic reply! Joe Koberg --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .