M-Bus Master on Raspberry Pi Pico

I have a working M-Bus Master implementation on the Raspberry Pi Pico, through a port of libmbus to the Pico C SDK.

The port itself was straightforward - the Pico’s hardware_uart API is easy to port to from libmbus’s current termios serial implementation.

To build pico-mbus:

Install the Pico C SDK if you haven’t already got it - pico-build provides a simple way of doing this
Clone and build pico-mbus

I’ve tested this, naturally, with the M-Bus Master Hat, although it should work with other M-Bus Master hardware serial implementations.

Wiring instructions are given in the README.

Here is the Pico output from scanning my M-Bus test rig, using mbus-scan, with slaves configured at addresses 1, 2 and 48.

------------
M-Bus: Start
M-Bus: Turn bus power on
M-Bus: Pause for 1000ms
M-Bus: Create serial context
M-Bus: Connect to serial
M-Bus: Using UART0
M-Bus: Set baudrate to 2400
M-Bus: TX Pin: 0
M-Bus: RX Pin: 1
M-Bus: Set flow control: CTS off RTS off
M-Bus: UART settings: Data 8 Stop 1 Parity 1
M-Bus: Set search retries value to 0
M-Bus: Scanning primary addresses:
Found an M-Bus device at address 1
Found an M-Bus device at address 2
Found an M-Bus device at address 48
M-Bus: Scan complete - results:
       Slaves found:    3
       Collisions:      0
       Addresses found: 1 2 48
M-Bus: Disconnect
M-Bus: Free context
M-Bus: Turn bus power off
M-Bus: Pause for 10000ms before rescanning

Here is the Pico output from querying, using mbus-query, device at address 48.

------------
M-Bus: Turn bus power on
M-Bus: Pause for 1000ms
M-Bus: Create serial context
M-Bus: Connect to serial
M-Bus: Using UART0
M-Bus: Set baudrate to 2400
M-Bus: TX Pin: 0
M-Bus: RX Pin: 1
M-Bus: Set flow control: CTS off RTS off
M-Bus: UART settings: Data 8 Stop 1 Parity 1
M-Bus: Initialize slaves
M-Bus: Primary address: 48
M-Bus: Query complete - results:
<?xml version="1.0" encoding="ISO-8859-1"?>
<MBusData>

    <SlaveInformation>
        <Id>30137315</Id>
        <Manufacturer>ATS</Manufacturer>
        <Version>1</Version>
        <ProductName></ProductName>
        <Medium>Heat: Outlet</Medium>
        <AccessNumber>207</AccessNumber>
        <Status>00</Status>
        <Signature>0000</Signature>
    </SlaveInformation>

    <DataRecord id="0">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Energy (kWh)</Unit>
        <Value>0</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="1">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Volume (1e-2  m^3)</Unit>
        <Value>5</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="2">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>On time (hours)</Unit>
        <Value>70254</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="3">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Power (kW)</Unit>
        <Value>1</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="4">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Volume flow (m m^3/h)</Unit>
        <Value>0</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="5">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Flow temperature (1e-2 deg C)</Unit>
        <Value>1</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="6">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Return temperature (1e-2 deg C)</Unit>
        <Value>1</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="7">
        <Function>Instantaneous value</Function>
        <StorageNumber>0</StorageNumber>
        <Unit>Temperature Difference (1e-2  deg C)</Unit>
        <Value>1</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

    <DataRecord id="8">
        <Function>Instantaneous value</Function>
        <StorageNumber>1</StorageNumber>
        <Unit>Time Point (date)</Unit>
        <Value>2023-09-02</Value>
        <Timestamp>1970-01-01T00:00:16Z</Timestamp>
    </DataRecord>

</MBusData>
M-Bus: Disconnect
M-Bus: Free context
M-Bus: Turn bus power off
M-Bus: Pause for 10000ms before requerying