DlmsCosemLib - an Arduino P1 DLMS/COSEM Decoder Library

Documentation

The DlmsCosemLib is a Arduino decoder Library for austrian el. energy meters with the P1 DLMS/COSEM interface.

Input is the already decrypted payload plaintext of the M-Bus message. The decoded records will be returned as a JSON.

Live test of the DlmsCosemLib Example at wokwi.com

A working P1 --> MQTT gateway with this library MBusinoP1

Credits

Thanks to DomiStyle for https://github.com/DomiStyle/esphome-dlms-meter where some ideas for decoding come from.

Thanks to HWHardsoft for the code base of this Library https://github.com/HWHardsoft/DLMS-MBUS-Reader

Class: DlmsCosemLib

Include and instantiate the DlmsCosemLib class.

#include <DlmsCosemLib.h>

DlmsCosemLib dlmsCosem;

Decoding

Method: decode

Decodes an already decrypted payload plaintext of the M-Bus message. The decoded records will be written as a JsonArray (requires ArduinoJson library). The result is an array of objects. The method call returns the number of decoded fields or negative numbers if error.

uint8_t decode(uint8_t *plaintext, uint8_t size, JsonArray& root);

same line from the example

fields = DlmsCosem.decode(&plaintext[0], sizeof(plaintext), root);

Example JSON output:

[{"timestamp":"27.09.2021 09:47:15"},
{"code":10,"obis":"1.0.1.8.0","name":"ActiveEnergyPlus","value_scaled":12937,"units":"Wh"},
{"code":11,"obis":"1.0.2.8.0","name":"ActiveEnergyMinus","value_scaled":0,"units":"Wh"},
{"code":8,"obis":"1.0.1.7.0","name":"ActivePowerPlus","value_scaled":0,"units":"W"},
{"code":9,"obis":"1.0.2.7.0","name":"ActivePowerMinus","value_scaled":0,"units":"W"},
{"code":1,"obis":"1.0.32.7.0","name":"VoltageL1","value_scaled":233.7,"units":"V"},
{"code":2,"obis":"1.0.52.7.0","name":"VoltageL2","value_scaled":0,"units":"V"},
{"code":3,"obis":"1.0.72.7.0","name":"VoltageL3","value_scaled":0,"units":"V"},
{"code":4,"obis":"1.0.31.7.0","name":"CurrentL1","value_scaled":0,"units":"A"},
{"code":5,"obis":"1.0.51.7.0","name":"CurrentL2","value_scaled":0,"units":"A"},
{"code":6,"obis":"1.0.71.7.0","name":"CurrentL3","value_scaled":0,"units":"A"},
{"code":7,"obis":"1.0.13.7.0","name":"PowerFactor","value_scaled":1,"units":""},
{"meter_number":"181220000009"}]

Example extract the JSON

      for (uint8_t i = 1; i < fields; i++) {
        const char *obisString = root[i]["obis"];
        const char *name = root[i]["name"];
        const char *units = root[i]["units"];
        double value = root[i]["value_scaled"].as<double>();
        
        send or process the records    
      }

You will find more details in the example

possible contained records

only contained records will be sended

• ["obisString"] contains the OBIS Code as ASCII array.
• ["value_scaled"] contains the value of the record as 64 bit real
• ["units"] contains the unit of the value as ASCII array
• ["name"] contains the name of the value as ASCII array
• ["meterNumber"] countains the serial Number of the meter
• ["timestamp"] countains the timestamp of the records

Method: getError

Returns the last error as ASCII array.

• Unsupported OBIS header type
• Unsupported OBIS header length
• Unsupported OBIS header medium
• Unsupported OBIS data type

const char * getError(int8_t code);

Home Assistant

The returned units are Home Assistant compatible. There are two methods to get the right device- and state-classes for use as Home Assistant sensor.

const char* getDeviceClass(uint8_t code);

const char* getStateClass(uint8_t code);

References

• Netz NÖ P1 Kundenschnittstelle

License

The DlmsCosemLib library is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

The DlmsCosemLib library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with the MBusinoLib library. If not, see http://www.gnu.org/licenses/.