Exmbus

Elixir M-Bus & Wireless M-Bus (wM-bus) parser library.

Installation

The package can be installed by adding exmbus to your list of dependencies in mix.exs:

def deps do
  [
    {:exmbus, "~> 0.2.0"}
  ]
end

Features

• M-bus
• wM-bus
• TPL Encryption modes: 0, 5
• (partly) supports ELL (supports encryption modes: 0 (none), 1 (aes_128_ctr)
• Compact Frames and Format Frames
• Compact Profiles
• VIF extension tables 0xFD and 0xFB (with a few exceptions)

Planned

• Transition the parser fully to handler + context based, and avoid raising on error but instead attach an error to the context. The APL layer in particular needs a lot of work here.
• Better API for encryption key storage.
• DLL CRC support.
• Split parsing and decoding into two steps. Currently the code parses the binary and decodes it in the same walk, but this causes errors when we can't decode an unsupported feature.

Not Planned

• Authentication and Fragmentation layer CI=90

Examples

Parse wM-Bus

This is an example from the OMS Vol2 Annex N - N.2.1. wM-Bus Meter with Security profile A

Exmbus.parse! will return an Exmbus.Parser.Context struct as the result.

iex> "2E4493157856341233037A2A0020255923C95AAA26D1B2E7493B013EC4A6F6D3529B520EDFF0EA6DEFC99D6D69EBF3"
...> |> Base.decode16!()
...> |> Exmbus.parse!(key: Base.decode16!("0102030405060708090A0B0C0D0E0F11"))
%Exmbus.Parser.Context{
  bin: "",
  opts: %{
    length: false,
    key: <<1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17>>,
    crc: false
  },
  handlers: [],
  handler: &Exmbus.Parser.Apl.FullFrame.maybe_expand_compact_profiles/1,
  dll: %Exmbus.Parser.Dll.Wmbus{
    control: :snd_nr,
    manufacturer: "ELS",
    identification_no: 12345678,
    version: 51,
    device: :gas
  },
  ell: %Exmbus.Parser.Ell.None{},
  tpl: %Exmbus.Parser.Tpl{
    frame_type: :full_frame,
    header: %Exmbus.Parser.Tpl.Header.Short{
      access_no: 42,
      status: %Exmbus.Parser.Tpl.Status{
        manufacturer_status: 0,
        temporary_error: false,
        permanent_error: false,
        low_power: false,
        application_status: :no_error
      },
      configuration_field: %Exmbus.Parser.Tpl.ConfigurationField{
        hop_count: 0,
        repeater_access: 0,
        content_of_message: 0,
        mode: 5,
        syncrony: true,
        accessibility: false,
        bidirectional: false,
        blocks: 2
      }
    }
  },
  apl: %Exmbus.Parser.Apl.FullFrame{
    records: [
      %Exmbus.Parser.Apl.DataRecord{
        header: %Exmbus.Parser.Apl.DataRecord.Header{
          dib_bytes: "\f",
          vib_bytes: <<20>>,
          dib: %Exmbus.Parser.Apl.DataRecord.DataInformationBlock{
            device: 0,
            tariff: 0,
            storage: 0,
            function_field: :instantaneous,
            data_type: :bcd,
            size: 32
          },
          vib: %Exmbus.Parser.Apl.DataRecord.ValueInformationBlock{
            description: :volume,
            multiplier: 0.01,
            unit: "m^3",
            extensions: [],
            coding: nil,
            table: :main
          },
          coding: :type_a
        },
        data: 2850427
      },
      %Exmbus.Parser.Apl.DataRecord{
        header: %Exmbus.Parser.Apl.DataRecord.Header{
          dib_bytes: <<4>>,
          vib_bytes: "m",
          dib: %Exmbus.Parser.Apl.DataRecord.DataInformationBlock{
            device: 0,
            tariff: 0,
            storage: 0,
            function_field: :instantaneous,
            data_type: :int_or_bin,
            size: 32
          },
          vib: %Exmbus.Parser.Apl.DataRecord.ValueInformationBlock{
            description: :naive_datetime,
            multiplier: nil,
            unit: nil,
            extensions: [],
            coding: :type_f,
            table: :main
          },
          coding: :type_f
        },
        data: ~N[2008-05-31 23:50:00]
      },
      %Exmbus.Parser.Apl.DataRecord{
        header: %Exmbus.Parser.Apl.DataRecord.Header{
          dib_bytes: <<2>>,
          vib_bytes: <<253, 23>>,
          dib: %Exmbus.Parser.Apl.DataRecord.DataInformationBlock{
            device: 0,
            tariff: 0,
            storage: 0,
            function_field: :instantaneous,
            data_type: :int_or_bin,
            size: 16
          },
          vib: %Exmbus.Parser.Apl.DataRecord.ValueInformationBlock{
            description: :error_flags,
            multiplier: nil,
            unit: nil,
            extensions: [],
            coding: :type_d,
            table: :fd
          },
          coding: :type_d
        },
        data: [false, false, false, false, false, false, false, false, false,
         false, false, false, false, false, false, false]
      }
    ],
    manufacturer_bytes: ""
  },
  dib: nil,
  vib: nil,
  errors: [],
  warnings: []
}

Testing

mix test

Benchmarks

Using Benchee, located in benchmarks/. Run with

mix run benchmarks/<name>.exs

Profiling

Some profiling scripts are available under profiling/.

You can run then with e.g. eprof:

 mix profile.eprof profiling/oms_vol2_annex_n.exs

TODO

• Implement examples from documentation as tests.
• Implement Authentication and fragmentation layer CI=90 Example: 4474260730381029078C20EF900F002C2503A2F08F49703C7E1904BAF77ACF00300710E1AC2507238AF96DE27F1F5B28D2437F5D8A05E7ACE10AA95F84000F6E63856AD8870BE28AEED46ED706E81C3472FCBB
• DLL CRC support. Currently CRC is hand-stripped from the specification examples.