M-Bus Data — M-Bus Meter Test Tool

What it does

M-Bus Data (formerly the M-Bus Meter Test Tool) is a Windows program we built to check quickly whether an M-Bus meter can be read through an M-Bus converter. It is written mainly for meter manufacturers: they plug the converter they were given into a computer and see, at their own bench, whether their meters talk to our reading infrastructure.

The program is released to meter manufacturers free of charge. It is a single executable. Nothing needs installing; it opens with a double-click and also runs from a USB stick. It asks for no tenant or apartment details, only meter and measurement data. The simplicity is deliberate: the goal is not billing but a clear answer to one question, does this meter read on this bus?

Each row shows its result in colour: green for read, red for no response, yellow for a reply whose telegram could not be decoded. For a meter that reads, index values, flow and return temperatures and flow rate go into the table. The selected meter's full telegram records and the cleaned raw frame in HEX can be inspected in the lower panel.

How it works

The user picks a COM port, enters the meter number and type (heat meter, hot water, cold water) and clicks "Start reading". The program opens the port itself, reads the meters in turn and closes the port when finished; there is no separate "connect" button. A converter plugged in while the program is running appears in the port list within seconds. The last port and the meter list are saved in a settings file next to the executable and come back on the next launch.

Three features help with long meter lists:

• Batch add: a sequential number range (leading zeros are kept) or a list pasted from Excel or an email. A preview shows how many meters will be added, and duplicates are skipped.
• Meter scan: if the numbers are unknown, the program searches the bus. In a secondary address scan you type the digits you know and leave the rest as F; if several meters answer at once, the search narrows by one more digit. A primary address scan queries each address from 0 to 250. Number, manufacturer and type are read from the identification field of the returned telegram.
• Read unread meters: only failed or untried meters are retried. Right-clicking a row reads just that meter, or everything from that row down.

A strip under the table shows total, read, failed and remaining counts, so progress through hundreds of rows is visible without scrolling.

When a meter does not answer

Retry count, command delay, delay between retries and port timeout are adjustable. Check the COM port and baud rate first (most meters use 2400, some 9600), then try a longer command delay for slow meters. "Repeat from the start" reads the list in a loop for endurance testing. A log of every byte sent and received is kept in the background and can be saved to a file when our support team asks for it.

Technology

M-Bus Data is a Python desktop application with a Qt interface, packaged as a single file. Communication follows the EN 13757 M-Bus structure: silencing the bus (SND_NKE), waking a meter by its number (SND_UD) and requesting its data (REQ_UD2), over a serial port set to 8 data bits, even parity and 1 stop bit.

The commands match those of our M-Bus Meter Reading software, and automated tests compare the two byte for byte, so a meter that reads in the test tool has been queried exactly as the main program would query it. The wake-up command has two forms and some meters answer only one, so retries alternate between them. Stray bytes on the bus before a frame are discarded, but every discard is logged; data is never changed silently.

The program updates itself only from our own domain over https, and a download whose SHA-256 fingerprint does not match is not installed. Without internet it keeps working without warnings, since manufacturers often use offline workshop computers.

Where it is used

• Manufacturers testing a meter model's M-Bus communication with a converter at their bench
• Finding meters with unknown numbers by scanning the bus
• Separating "no response" from "response that could not be decoded" and sharing the raw telegram and byte log with support
• Watching how a bus and its meters hold up over long looped reading runs

After testing, meters are read day to day with our M-Bus Meter Reading software and M-Bus Master devices.

Product site

The current version and a step-by-step user guide are on the M-Bus Data guide page at m-bus.com.tr.