M-bus master chipset

[vinodstanur]

I am looking for a dedicated m-bus master chipset to interface with a 3V MCU. System runs on a 3.7V 3Ah LiPo. I can try with a boost converter for m-bus logic level and some BJT based circuitry combining with UART of the stm32 MCU, but is there any better solution than implementing it using any dedicated M-BUS master IC which takes care of the voltage boosting, level converting etc?

 

[FvM]

Never saw dedicated M-Bus master IC. Requirements are too different, I believe.

 

[vinodstanur]

My application involves a battery-powered device that reads multiple water meters every 15 minutes and syncs the data via NB-IoT to the cloud. I have not yet worked with M-Bus, so I am exploring how to implement a master device in this setup while optimizing for power consumption. The system needs to briefly boost 3.6V to 36V when reading the M-Bus meters. I’m considering using discrete BJT components for the circuit, but I’m open to suggestions for more efficient approaches.

 

[FvM]

M-Bus spec has large margin for cable voltage drop, depending on your harware setup, you me able to reduce bus voltage. I understand your latest post so that you are only temporarily powering M-Bus which should be o.k. for most M-Bus slaves, but requires an internal (e.g. battery) power supply of the meter to accumulate data during M-Bus power-down. Slaves are required to be ready 3 secs after applying M-Bus voltage.

 

[vinodstanur]

Oh, I hadn’t realized that the entire M-Bus slave, including the sensing operation, is typically powered from the bus itself. I initially assumed only the transceiver front-end would be powered via the bus voltage. But yes, unless the sensor has its own internal battery or power supply, it makes sense that the bus needs to supply everything. I’ll check the specific sensor I’m planning to use — hopefully it has an internal battery and isn’t fully dependent on M-Bus power delivery. Mine is water meter.

 

[FvM]

You need to check the details. An electronical water meter is usually battery powered, an optional M-Bus interface can be powered down without loosing data. In a mechanical water meter with M-Bus readout, the readout is typically M-Bus powered and only counting pulses. To keep counter state, M-Bus must stay powered.

 

[vinodstanur]

I'm currently looking for an open-source M-Bus (EN 13757-compliant) master library written in bare-metal ANSI C, suitable for use in memory-constrained embedded environments (e.g., STM32 with no OS or a lightweight RTOS).

Most available implementations—such as libmbus—are designed for desktop environments (Linux/Windows), making them bulky and unsuitable for direct integration into MCUs without significant manual porting.

Am I missing a lightweight, MCU-friendly M-Bus master stack—something akin to nanomodbus but for M-Bus? Ideally, it would provide basic master functionality like REQ_UD2, response parsing, and minimal memory footprint, with no OS or socket dependencies.

Any leads or recommendations would be greatly appreciated!