WMBus RX - portapack-mayhem/mayhem-firmware GitHub Wiki

WMBus RX

Receives and decodes Wireless M-Bus (wM-Bus) telemetry from utility meters — water, gas, heat and electricity meters that report over radio in the 868 MHz band.

This is an external app (.ppma file on the SD card).

Overview

Wireless M-Bus (EN 13757) is the European standard that smart utility meters use to transmit consumption and status data by radio. The app receives these packets, validates each one with the wM-Bus CRC, and decodes the meter's identity and — for unencrypted frames — the reported values.

Select the mode that matches the meter, tune to the matching frequency, and received packets appear in the console.

Mode	Frequency	Notes
T-Mode	868.95 MHz	3-of-6 chip coding (default mode)
C-Mode	868.95 MHz	compact mode
S-Mode	868.3 MHz	slower, stationary mode

The app does not retune automatically — set the frequency field to the frequency shown above for the selected mode.

Controls

Control	Description
Mode	wM-Bus mode: T / C / S (see table above).
Frequency	Tune to the mode's frequency (10 kHz steps).
RF Amp	RF amplifier: `0` = off, `1` = on (+14 dB).
LNA	IF gain (0–40 dB). See Receive Quality Issues.
VGA	Baseband gain (0–62 dB).
RSSI / Channel	Signal strength and channel power meters.
Last Err	Reason the last frame was rejected (CRC fail, length error, coding error …) or `None`.

Decoded fields

For each valid packet the console shows:

Field	Meaning
Mfr	Manufacturer — 3-letter flag code decoded from the meter header
ID	Meter serial number (hex)
Ver	Device version byte
Type	Device / medium type — e.g. Water, Cold water, Hot water, Gas, Electricity, Heat, Heat cost allocator, Smoke detector
CI / Enc	Control-information byte and encryption status: `None`, `AES-128`, `DES` or `Mode n`
V:	Up to three decoded data values (shown only for unencrypted frames)
Hex	Raw hex dump of the frame

Encrypted frames (AES-128 / DES) are identified but their values cannot be read without the key.

Protocol

Wireless M-Bus (EN 13757-4) operates in the 868 MHz short-range band using FSK. T-Mode uses 3-of-6 chip coding, C-Mode is the newer compact mode, and S-Mode is the slower stationary mode. Each frame is verified with the wM-Bus CRC (polynomial 0x3D65) before it is decoded.