cidermole / dbus-cgwacs

dbus-cgwacs

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

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.