M-Bus Driver

dc3-driver-mbus reads heat, water, and gas meters over the M-Bus (Meter-Bus, EN 13757) wired bus. It builds REQ_UD2 requests, SND_NKE/SND_UD frames, verifies the response checksum, and decodes the data records into values.

Protocol background

M-Bus (EN 13757) is the European standard for remote meter reading. A master sends short frames to address a meter by primary address, and the meter replies with a long frame containing a variable-length data record (DIF/VIF/data) that carries the measured quantity.

• Driver name / code: M-Bus Driver / MbusDriver
• Type: DRIVER_CLIENT (opens the serial port and polls the meter)
• Underlying library: jSerialComm (self-built EN 13757-2/3 frame encode/decode — no native jrxtx dependency)

Attribute configuration

Driver attributes (device-level driver-attribute)

Attribute	code	Type	Default	Description
Serial Port	port	STRING	/dev/ttyUSB0	Serial port device path
Baud Rate	baudRate	INT	2400	Baud rate (M-Bus default 2400)
Data Bits	dataBits	INT	8	Data bits
Stop Bits	stopBits	INT	1	Stop bits
Parity	parity	INT	2	Parity (2=Even)
Timeout	timeout	INT	1000	Read timeout in milliseconds
Primary Address	primaryAddress	INT	0	M-Bus primary address (0-250)

Point attributes (point-attribute)

Attribute	code	Type	Default	Description
Record Index	recordIndex	INT	0	0-based index of the data record to read
Data Format	dataFormat	STRING	FLOAT	Data format: FLOAT, HEX, ASCII

Collection and health

• Collection cycle: default cron 0/30 * * * * ? (one polling round over all points every 30 seconds).
• Health/online: device health defaults to cron 0/15 * * * * ?, lease timeout 45 seconds.

Capability matrix

Capability	Supported	Notes
Read	✓
Write	✓ (SND_NKE reset and SND_UD select frames)
Subscribe	—

Implementation status: available ::

Frames are self-built (no native jrxtx dependency); MbusFrame handles REQ_UD2/SND_NKE/SND_UD building, checksum verification, and DIF/VIF record parsing.

Minimal onboarding example

1. Create a Device using M-Bus Driver, set port=/dev/ttyUSB0, baudRate=2400, parity=2, primaryAddress=0.
2. Add a Point (READ_ONLY) with recordIndex=0 and dataFormat=FLOAT.
3. Start the driver; within 30 seconds the value appears in PointValue.

Further reading

• Driver overview — entry point to all protocol drivers and selection
• Driver capability matrix — quick reference of read/write/subscribe capabilities
• Device onboarding — a complete onboarding walkthrough