RF communication is finally working. It wasn't easy to get those cheap chinese RF modules working but this library helped me a lot.
Two new commands have been added:
--RFCH<xxx> - set RF channel (0-127)
--AD<aaaaaaaaaa> - set 5-byte address for RF communication (HEX)
These two commands are also used for setting the USB dongle on PC side, which must have the same channel and address as energy meter you want communicate with.