dbus-cgwacs

Reads energy measuremens from Carlo Gavazzi Wired AC Sensors (hence cgwacs), and puts in on the D-Bus. Supported models: EM24, ET112, ET340, EM530, EM540 and selected EM-300 models.

EM530/540 support

Note that for the EM530 and EM540, only Sub-family X and PFC is supported.

Family	Sub-family	Part number	Measurement
EM530-IS	X	EM530DINAV53XS1X	CT
	PFC	EM530DINAV53XS1PFC	CT
EM540-IS	X	EM540DINAV23XS1X	Internal
	PFC	EM540DINAV23XS1PFC	Internal

EM300 support

For the EM-300 series of meters, only the series-27 meters are supported, and only X and PFB models are supported. The series-27 is a meter that simulates (in part) the registers of an EM24. The following part numbers are supported. Note the 27 series appended at the end of the part number.

Family	Sub-family	Part number	Measurement
EM330	X	EM330DINAV53HS1X27	CT
	PFB	EM330DINAV53HS1PFB27	CT
EM340	X	EM340DINAV23XS1X27	Internal
	PFB	EM340DINAV23XS1PFB27	Internal

Energy counters

• With the exception of the ET340, all 3-phase meters lack per-phase reverse energy counters. Only a total energy value is available. dbus-cgwacs estimates the per-phase reverse energy by using the proportion of negative reverse power of each phase.

• The total energy counters on the EM300 series (the ET340 and the EM-300-series-27) is simply the sum of the individual phase counters. It does not aggregate the total across all the phases, therefore resulting in a different outcome. Where energy is simultaneously imported and exported on different phases, the EM24 and EM530/540 will correctly show the total energy across all phases, while the other meters will show higher import and export numbers that may not correspond with the utility meter.

Architecture

The application consists of several layers:

• Data acquisition layer:
  • The ModbusRtu class provides a simple implementation of the modbus RTU protocol, which supports the functions ReadHoldingRegisters (3), ReadInputRegisters (4) and WriteSingleRegister (6) only.
  • AcSensorUpdater connects to an ac sensor, retrieves its identity (type & serial) and retrieves measured data. The data retrieved will be stored in an AcSensor object.
• Data model
  • AcSensor contains the latest measurements taken from an AC sensor.
  • Settings Persistent settings objects which contains global settings.
  • AcSensorSettings Persistent AC sensor settings.
• D-Bus layer
  • AcSensorBridge produces the com.victronenergy.grid.ttyUSB?? D-Bus service. Information is taken from an AcSensor, and an AcSensorSettings object.
  • AcSensorSettingsBridge consumes a subtree from the local settings. Path: /Settings/CGwacs/D[serial]

Finally AcSensorMediator ties everything together.

Error handling

It is important for dbus-cgwacs to terminate if it is not talking to a Carlo Gavazzi meter, otherwise serial-starter cannot work properly. Two kinds of errors are possible.

• A timeout:
  • There was no response to a modbus request. The default timeout is 250ms (2 seconds for zigbee) and can be overridden with the --timeout commandline option.
  • dbus-cgwacs will terminate after 5 consecutive requests ends in a timeout.
• A modbus error:
  • These include outright errors such as unsupported registers or CRC errors.
  • In order to be forgiving to intermittent conditions causing CRC errors, dbus-cgwacs will terminate after 20 consecutive errors.