Arduino library for interfacing with Dutch smart meters implementing DSMR
Clone or download
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
examples Add minimal parsing example Sep 18, 2018
src fixup! Remove some unused parameter names Sep 18, 2018
README.md Remove reference to (long merged) PR for SoftwareSerial Sep 18, 2018
library.properties Add category to library.properties Dec 1, 2015

README.md

Arduino Dutch Smart meter (DSMR) parser

This is an Arduino library for interfacing with Dutch smart meters, through their P1 port. This library can take care of controlling the "request" pin, reading messages and parsing them.

This code was written for Arduino, but most of the parsing code it is pretty generic C++ (except for the Arduino- and AVR-based string handling), so it should be possible to adapt for use outside of the Arduino environment.

When using Arduino, version 1.6.6 or above is required because this library needs C++11 support which was enabled in that version.

Protocol

Every smart meter in the Netherlands has to comply with the Dutch Smart Meter Requirements (DSMR). At the time of writing, DSMR 4.x is the current version. The DSMR 5.0 P1 specification is available and expected to be used in smart meters starting in 2016. This code should support both the 4.x and 5.0 specifications. 3.x meters might also work, but this has not been verified or tested (feedback welcome).

The DSMR specifications can be found on the site of Netbeheer Nederland. Of particualr interest is the "P1 companion standard" that specifies the P1 port (here's some useful versions: 3.0, 4.0.7, 4.2.2, 5.0).

According to DSMR, every smart electricity meter needs to have a P1 port. This is a 6p6c socket (commonly, but incorrectly referred to as RJ11 or RJ12). Telephone plugs will fit, provided that you have some that actually have 6 pins wired, or you have just 4 and do not need power from the P1 port.

Pinouts and electrical specs can best be looked up in the spec (The 5.0 version is the most clear in this regard, though not everything may apply to 4.x meters).

Note that the message format for the P1 port is based on the IEC 62056-21 "mode D" format. That spec is not available for free, though there seem to be a version available on the net. DLMS also seems a related standard, but that apparently defines a binary format. It does seem all of these use "OBIS identifiers" and "COSEM data objects" (DLMS has some lists of objects, of which 1001-7 seems to somewhat match th DSMR specs), to describe the various properties, though it's not entirely clear how all of these fit together. However, the DSMR spec has a complete, though sometimes confusing list of fields used.

A typical P1 message looks something like this:

/KFM5KAIFA-METER

1-0:1.8.1(000671.578*kWh)
1-0:1.7.0(00.318*kW)
!1E1D

This includes an identification header at the top, a checksum at the bottom, and one or more lines of data in the middle. This example is really stripped down, real messages will have more data in them.

The first part of the line (e.g. 1-0:1.8.1) is the (OBIS) id of the field, which defines the meaning and format of the rest of the line.

Parsing a message

Unlike other solutions floating around (which typically do some pattern matching to extract the data they need), this code properly parses messages, verifying the checksum and really parses each line according to the specifications. This should make for more reliable parsing, and allows for useful parser error messages:

1-0:1.8.1(000671.578*XWh)
                     ^
Error: Invalid unit

1-0:1.8.1(0006#71.578*kWh)
              ^
Error: Invalid number

!6F4A
 ^
Checksum mismatch

This library uses C++ templates extensively. This allows defining a custom datatype by listing the fields you are interested in, and then all necessary parsing will happen automatically. The code generated parses each line in the message in turn and for each line loops over the fields in the datatype to find one whose ID matches. If found, the value is parsed and stored into the corresponding field.

As an example, consider we want to parse the identification and current power fields in the example message above. We define a datatype:

using MyData = ParsedData<
  /* String */ identification,
  /* FixedValue */ power_delivered
>;

The syntax is a bit weird because of the template magic used, but the above essentially defines a struct with members for each field to be parsed. For each field, there is also an associated xxx_present member, which can be used to check whether the field was present in the parsed data (if it is false, the associated field contains uninitialized data). There is some extra stuff in the background, but the MyData can be used just like the below struct. It also takes up the same amount of space.

struct MyData {
	bool identification_present;
	String identification;
	bool power_delivered_present;
	FixedValue power_delivered;
};

After this, call the parser. By passing our custom datatype defined above, the parser knows what fields to look for.

  MyData data;
  ParseResult<void> res = P1Parser::parse(&data, msg, lengthof(msg));

Finally, we can check if the parsing was succesful and access the parsed values as members of data:

  if (!res.err && res.all_present()) {
    // Succesfully parsed, print results:
    Serial.println(data.identification);
    Serial.print(data.power_delivered.int_val());
    Serial.println("W");
  }

In this case, we check whether parsing was successful, but also check that all defined fields were present in the parsed message (using the all_present() method), to prevent printing undefined values. If you want to support optional fields, you can use the xxx_present members for each field individually instead.

Additionally, this template approach allows looping over all available fields in a generic way, for example to print the parse results with just a few lines of code. See the parse and read examples for how this works.

Note that these examples contain the full list of supported fields, which causes parsing and printing code to be generated for all those fields, even if they are not present in the output you want to parse. It is recommended to limit the list of fields to just the ones that you need, to make the parsing and printing code smaller and faster.

Parsed value types

Some values are parsed to an Arduino String value or C++ integer type, those should be fairly straightforward. There are three special types that need some explanation: FixedValue and TimestampedFixedValue.

When looking at the DSMR P1 format, it defines a floating point format. It is described as Fn(x,y), where n is the total number of (decimal) digits, of which at least x and at most y are behind the decimal separator (e.g. fractional digits).

However, this floating point format is a lot more limited than the C float format. For one, it is decimal-based, not binary. Furthermore, the decimal separator doesn't float very far, the biggest value for y used is 3. Even more, it seems that for any given field, there is no actual floating involved, fields have x equal to y, so the number of fractional digits is fixed.

Because of this, parsing into a float value isn't really useful (and on the Arduino, which doesn't have an FPU, very inefficient too). For this reason, we use the FixedValue type, which stores the value as an integer, in thousands of the original unit. This means that a value of 1.234kWh is stored as 1234 (effectively the value has been translated to Wh).

If you access the field directly, it will automatically be converted to float, keeping the original value. Alternatively, if an integer version is sufficient, you can call the int_val() method to get the integer version returned.

// Print as float, in kW
Serial.print(data.power_delivered);
// Print as integer, in W
Serial.print(data.power_delivered.int_val());

Additionally there is a TimestampedFixedValue method, which works identically, but additionally has a timestamp() method which returns the timestamp sent along with the value.

These timestamps are returned as a string, exactly as present in the P1 message (YYMMDDhhmmssX, where X is S or W for summer- or wintertime). Parsing these into something like a UNIX timestamp is tricky (think leap years and seconds) and of limited use, so this just keeps the original format.

Connecting the P1 port

The P1 port essentially consists of three parts:

  • A 5V power supply (this was not present in 3.x).
  • A serial TX pin. This sends meter data using 0/5V signalling, using idle low. Note that this is the voltage level commonly referred to as "TTL serial", but the polarity is reversed (more like RS232). This port uses 115200 bps 8N1 (3.x and before used 9600 bps).
  • A request pin - 5V needs to be applied to this pin to start generating output on the TX pin.

To connect to an Arduino that has an unused hardware serial port (like an Arduino Mega, Leonardo or Micro), the signal has to inverted. This can be done using a dedicated inverter IC, or just a transistor and some resistors.

It's also possible to do all of the serial reception, including the inverting, in software using Arduino's SoftwareSerial library. However, it seems there are still occasional reception errors when using SoftwareSerial.

Slave meters

In addition to a smart electricity meter, there can be additional slave meters attached (e.g., gas, water, thermal and slave electricity meter). These can talk to the main meter using the (wired or wireless) MBUS protocol to regularly (hourly for 4.x, every 5 minutes for 5.0) send over their meter readings. Based on the configuration / connection, each of these slaves gets an MBUS identifier (1-4).

In the P1 message, this identifier is used as the second number in the OBIS identifiers for the fields for the slave. Currently, the code has the assignment from MBUS identifier to device type hardcoded in fields.h. For the most common configuration of an electricity meter with a single gas meter as slave, this works straight away. Other configurations might need changes to fields.h to work.

License

All of the code and documentation in this library is licensed under the MIT license, with the exception of the examples, which are licensed under an even more liberal license.