Hi Mr. Taylor,
I made changes of USBDemo picbasic code according your advice and after compilation I obtain error messages:

Error[113 ] c:\pbp_prog\usbdemo.asm 61 : Symbol not previously defined (ADRead)
Error[113 ] c:\pbp_prog\usbdemo.asm 62 : Symbol not previously defined (ADRead)

I do not know why is happen?

Thanks,
Kuba230