This commit fixes the driver to respect the new device
registration mechanism via hw_proxy.rs232_devices.
It also refactors the code to more easily support multiple
scale protocols, and introduces support for the ADAM Equipment
AZExtra scale protocol. (Might be compatible with other ADAM
Equipment scales)
Support for th AZExtra scale is experimental at the moment,
especially given two annoying problems with this model:
- they do not support proper probing (stays mute until a
non-zero weight is measured), so they have to be probed
last and *assumed* to work
- the scale beeps when a read attempt is made and the
weight is not stable yet, or the weight has been already
read previously. This constant beeping during operation
is mitigated by extra delays between readings, but might
still prove to be a major issue for supporting this scale.
f579acf02f