M-Bus Slave Click

How does it work?

M-Bus is a bus system used for the remote reading of gas, water, heat, electricity, etc. It also supports various sensors and actuators. This is a cost-optimized bus for the transfer of energy consumption data since it is made for communication on only two wires. M-Bus can be used in the industry, but also, it’s convenient to be used in private households. By the standard, M-Bus master can read up to 250 slave devices. They can be meters, water, electrical, or gas meters. You can also use M-bus in applications like alarm systems, flexible illumination installations, heating control, etc. It can monitor different consumption meters, and it can monitor any leakage.

One of the biggest advantages of M-Bus are:

• All data reading is accomplished remotely.
• It is a very simple protocol – it uses only two wires, and it uses power supply from the users which are connected to the wire.
• Reading errors are minimal. Also, reading is very fast. Further processing is very easy since the received data is presented in a machine readable form.
• There are no special cables – you can use a telephone cable. With that one cable, you can attach all the meters in the housing with all the meters individually addressable. This way you can have control over each consumption meter while using only one connection cable.

M-Bus Slave Click uses the TSS721A, a single chip transceiver developed for Meter-Bus standard (EN1434-3) applications. The connection to the bus is polarity independent and serves as a slave node in the system. M-Bus Slave Click has full galvanic isolation with optocouplers to improve the reliability of the whole circuit. The circuit is supplied by the master via the bus. The benefit of the TSS721A in M-Bus slaves is the reduction of the number of components needed, and therefore the cost of slaves. Apart from the transmission and reception of data by the M-Bus specification, this IC also provides translation from and to the operating voltage of the microprocessor to which it is connected, to be able to communicate with it. The communication can take place at baudrates from 300 to 9600 Baud. Additional features include integrated protection against reversed polarity, a constant 3.3V power supply for the microprocessor, and the prompt indication of failure of the bus voltage.

Specifications

Pinout diagram

This table shows how the pinout on M-Bus Slave Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	NC
	NC	3	CS	RX	14	TX	UART TX
	NC	4	SCK	TX	13	RX	UART RX
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

M-Bus Slave Click electrical specifications

Software Support

We provide a library for the M-Bus Click on our LibStock page, as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Library Description

The library covers all the necessary functions to control M-Bus Slave Click board. Library performs a standard UART interface communication.

Key functions:

• void mbus_write_byte ( uint8_t input ) – Write Single Byte.
• uint8_t mbus_read_byte( void ) – Read Single Byte.
• uint8_t mbus_byte_ready ( void ) – Check for new byte received.

Examples description

The application is composed of three sections :

• System Initialization – Initializes peripherals.
• Application Initialization – Initializes UART serial interface and app mode.
• Application Task – (code snippet) This is an example that demonstrates the use of the M-BUS Click board. In this example, depending on the app mode selected, we send ( receive ) a message to ( from ) the M-BUS Master Click which is connected via cable to M-BUS Click ( slave ). Results are being sent to the Usart Terminal where you can track their changes. All data logs write on USB uart changes approximately for every 2 sec.

void application_task ( )
{
    char tmp;
    uint8_t drdy_flag;

    if ( app_mode == APP_MODE_RECEIVER )
    {
        // RECEIVER - UART polling 

        drdy_flag = mbus_byte_ready( );

        if ( 1 == drdy_flag )
        {
            tmp = mbus_read_byte( );
            mikrobus_logWrite( &tmp, _LOG_BYTE );
        }
    }
    else
    {
        // TRANSMITER - TX each 2 sec
      
        for ( tmp = 0; tmp < 9; tmp++ )
        {
            mbus_write_byte( demo_message_data[ tmp ] );
            mikrobus_logWrite( " >> MESSAGE SENT <<", _LOG_LINE );
            Delay_ms( 100 );
        }
        
        Delay_ms( 2000 );
    }
}

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• UART

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.