OK now try the following
Code:
calibre-debug -c "from calibre.devices.scanner import DeviceScanner; s = DeviceScanner(); s.scan(); print s.devices"
calibre-debug -c "from calibre.devices.scanner import DeviceScanner; from calibre.devices.prs505.driver import PRS505; s = DeviceScanner(); s.scan(); print s.is_device_connected(PRS505);"