The iSMA-B-MG-IP serves as an M-Bus gateway using either one of two protocols: TCP IP or UDP IP.
M-Bus TCP IP Gateway
The device simultaneously supports up to 4 M-Bus TCP clients. If the fifth device is to be connected to the meter gateway, TCP connection will be rejected. In order to secure the meter gateway before filling up the call list, a mechanism for monitoring each M-Bus TCP IP connection was introduced. Every 45 seconds a query is sent to the devices connected to the bus. If a device does not response to the query, after 2 seconds another query is sent. If the device does not respond three times, the meter gateway closes the connection.
The iSMA-B-MG-IP device has a built-in M-Bus TCP IP to M-Bus interface gateway, which allows to connect additional 3rd party M-Bus devices using the bus. In order to ensure proper operation of the M-Bus gateway, please make sure that the baud rate of the M-Bus interface of all the devices connected to the bus (gateway and an addition devices) are the same.
Operation of the gateway is based on sending the M-Bus TCP IP query by the M-Bus. Data frame from query is converted to M-Bus and sent to the bus. Then the iSMA-B-MG-IP device waits for an answer from a device connected to the bus; if the meter does not respond within the estimated time defined by the M-Bus Timeout parameter (by default, 2000 ms), an exception is returned: error code 0x0B. If the slave answers the correct frame, it is converted to M-Bus TCP IP and sent to the master.
M-Bus UDP IP Gateway
The device simultaneously supports up to 2 M-Bus UDP clients. In order not to miss the second client’s packet delivery at high intensity periods of incoming data, the data from the first client is read from the lwIP in the loop, and only two frames are buffered with different addresses. The response via the UDP protocol is sent to the same port it came from (the default port for UDP protocol is 10002).
Both TCP and UDP protocols share the M-Bus interface: