3.6 Wireless M-Bus Interface

Wireless M-Bus Interface

This function is only available in 2N^® SmartCom PRO, which includes an optional Wireless M-Bus communication module. There are different WM-Bus interfaces according to the module mounted (radio frequency, e.g.). Up to 1000 meters can be configured for which the device shall collect readings. Having received a WM-Bus message from a meter defined in the meter list, 2N^® SmartCom PRO will store it into a circular buffer in the internal memory. The stored data can only be retrieved and deleted starting from the oldest record. When the memory is full, the oldest data will be deleted automatically to make space to new records. Define the minimum reading time interval for each meter. Any meter reading coming before the end of this interval will not be stored.

The 868 MHz WM-Bus module can work in four modes: T1, S1, C1 and T1+C. The 169 MHz module works in the N mode and the 433 MHz module in the T1 and C1 modes. They support encrypted messages too in all the modes. In the basic configuration, the terminal does not decrypt messages and stores them as they are received. Enter the correct encryption key and enable decryption to make the messages be decrypted by the module and stored in the decrypted format in the terminal memory. For security reasons, encryption keys are not stored in the memory, but written directly into the module. Therefore, if decryption does not work, check the device transmission and device settings in the terminal and re-enter the encryption key.

Explanation of Wireless M-Bus Commands

These commands are only implemented in 2N^® SmartCom PRO, which contains an optional Wireless M-Bus module. There can be up to 2 Wireless M-Bus modules in one device, each with a different frequency and message receiving mode. This is why the configuration is split into module 1 and module 2 sections. The common command section helps set the table of meters, their encryption keys and general WM-Bus packets as well as launch of the sniff mode. The purpose of the sniff mode is to capture packets from transmitters in the surroundings regardless of the meter list settings. Let us start with the common section called "scwmbfilter".

at^scwmbfilter="dev_add","MAN",12345678,01,37,600

• This command adds a meter to the meter list. MAN is a three-letter abbreviation of the manufacturer followed by the meter serial number. The following two parameters are also necessary for meter identification: Version and Device. Ask the device manufacturer for these values. Or intercept them using the sniffer, see below. The next parameter is the minimum interval in seconds between two readings of the meter to be added. If 0 is set, all messages received from the meter are stored.

at^scwmbfilter="dev_remove",1

• The command removes a meter from the meter list; the parameter defines the meter list position (1–1000).

at^scwmbfilter="dev_clear"

• The command clears the whole meter list.

at^scwmbfilter="key_add",1,A5B95C144134DE257AF2ED4F384C7EB7

• The command sets the encryption key for meter 1 in the 32 HEX format (each of the meters can have a key of its own).

at^scwmbfilter="key_remove",1

• The command deletes the encryption key for meter 1.

at^scwmbfilter="cf_discard",0

• The modules is switched into a mode in which it discards messages captured in the Compact Frame (CF) format and stores only the Full Frame messages.
  • 0 – disabled, all messages are saved.
  • 1 – enabled, CF messages are discarded.

at^scwmbfilter="cf_discard"

• The command displays the currently set value.

at^scwmbfilter="save"

• The command saves the currently set values.

at^scwmbfilter="sniff"

• The command switches the WM-Bus module into the sniff mode, which captures all messages from the devices in the surroundings and displays them via the console. Once you enter the command, a connect message will get displayed and the terminal starts writing out the messages. The message is as follows:

  at^scwmbfilter="sniff"
  CONNECT
  ^SCWMBFILTER: 1,"AMB",54001477,01,37,-1,-92dBm

  The message format and meanings of its elements are as follows: ^SCWMBFILTER: 1,"MAN",12345678,VER,DEV,ID,SIGNAL

  • 1 – number of the module that captured the packet.
  • MAN – manufacturer.
  • 12345678 – device serial number.
  • VER – meter version defined by the manufacturer.
  • DEV – type of the quantity to be measured (water / gas) defined by the manufacturer.
  • ID – meter list ID in the terminal; if no ID is assigned, the meter is not configured in the terminal and labelled with -1.
  • SIGNAL – signal level in the moment of message reception.

at^scwmbfilter="enable",1

• The command activates/deactivates a filter. All WM-Bus packets are received and saved if the function is disabled.

at^scwmbfilter="enable"

• The command displays the currently set value.

at^scwmbfilter="key_info"=1

• The command enables/disables encryption for the selected WM-Bus meter list item (meter list ID).

at^scwmbfilter="key_info"

• The command displays the currently set value; the encryption key is not listed for security reasons.

at^scwmbfilter?

• The command displays the defined meter list.

at^scwmbfilter=?

• The command displays the Wireless M-Bus filter setting options.

Module Parameters

The commands relate to the modules. There are two identical command sets with different module numbers and so you have to know the module number to be configured. Let us explain commands for module 1 only. Refer to S. 6 for a full list of commands.

at^scwmbus1="mode",11

• The command sets the operational mode for the device.
  
  • 1 – T1
  • 3 – S1
  • 8 – C1
  • 11 – T1+C
  • 17 – N1

at^scwmbus1="mode"

• The command displays the currently set mode.

at^scwmbus1="RF_channel"

• The command displays the currently set WM-Bus transmitting channel.

at^scwmbus1="RF_channel",1

• The parameter defines the WM-Bus transmitting channel. The setting options are 1–12. For selected modules only.

at^scwmbus1="RF_DATA_RATE"

• The command displays the currently set modulation (for RC1701 module only).

at^scwmbus1="RF_DATA_RATE",1

• The parameter sets the modulation. Select the ID that corresponds to the required setting. Refer the table below for details.
• MODE – must be set to mode 17 - N1.