Connector / protocol for elster gasmeter

Hi everbody,

I have a gasmeter from elster. There are different communication moduls available (mBus, radio, etc.). These modules can be via a 4 pin connector:

Does anybody know anything about this connector and how it can be used using own electronics?

Kind regards

I found out a bit about it: Electrically it is an UART interface where the counter is fed through the RX pin. In image top right pin is TX out and lower left pin is RX in. The remaning 2 Pins are GND. Protocolwise the device seems to use m-bus, for which a linux library is available.

Hi @Phunkafizer, i try to connect directly to the 4-pin interface since i only have the SCR+ Interface but not the modbus-adapter. do you have more information if this is possible and if so how/what voltage and protocol? seems there is very little information around for this 4-pin connector

cheers Kai

Hi Kai,

unfortunately I do not have any information about the SCR protocol, my gas meter was shipped in m-bus configuration. Voltage is 5 V, but a simple UART interface won’t work as the meter is supplied via the TX pin. You need a current amplifier (e. g. MOSFET) between the UART interface and the meter.


after weeks of googling around i finally found the protocol description!

“The SCR+ Communication Interface” AE02:03.01:01.01 Specification

Once you get the channel setup right (>4.5V and <6V) with 300baud its supposedly possible to interact easily via a simple ascii line protocol with the unit.

Lets see, will get my osci fire ed up and see if can decode it …

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Wow, also tried to find something about that protocol some time ago, but was not able to find it.
Do you have a SCM communication module and just want to pick up the data between it and the meter, or do you want to built an own communication module which will read out the meter?
For the modbus variant I did the latter with a battery powered ESP8266 module.

Direct upload of document in case link goes bad :wink:

TI_AE02_03.01_03.01_EN.pdf (137.3 KB)

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Ideally one (me) could just plug an ESP to the 4-pin port of the actual meter and read the meters impulses, avoiding any Com-Modul, is that what you built? would be perfect :wink:

I had the SCR module already preinstalled but guess it wont be too easy, when looking into the docs in detail. I guess its not that straight forward to build a SCR+ Adapter for an ESP or a RPi … at least for me :see_no_evil: If someone else feel like, here are some more insights I have so far

TX : You can send requests to the Meter by changing to input current

  • Imin = 0.5 mA (idle mode. The Meter waits for a command)
    • Inom = 4 mA (while the Meter reads out the mechanical rollers)
    • Imax = 30 mA (inrush current. See also chapter 2.1.2), kind of start the meter filling up a capacitor… most probably the most tricky part

RX : you can read from the meter with 300baud in standard EDIS 1995, OBIS 2005 or OMS 2.0.0 (depending on the type of meter you have), i guess at least OBIS 2005 is standardized in iec62056-21.

[edit - MOD]
Added as an attachment

iec62056-21{ed1.0}en_.pdf (2.4 MB)

I already have a working device which implements the physical layer, at least for the m-bus variant. I assume that the physical layer is identical, as the meter can be configured by the energyprovider in SCM or m-bus. If you are able to built firmware for a ESP8266 and flash it you could give it a try with one of my module, see attachment.

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Looks pretty neat! :slight_smile: Yet, would like to test it…

Hi Stefan,
I see, that you are also based in Fuerth as I am.
After I more or less unsuccessfully tried to read the BK-G4 AT via infrared and optical recognition, I’m also interested in your module.
I do have experieces with ESP32 and ESP8266 (mainly with Tasmota as OS).
Maybe we can also physically connect to get a working solution.
If you are interested, you can also send me a PM.


Hi Jörg,

my project is almost finished, I’ll let you know when it’s done. If you have questions you can leave me a PN.


Hi @Phunkafizer,
thanks for the info.
I’ll wait for your update.


Could you guys report to me the type IDs of your meters? It starts with “AE”, for example for my meter it’s “AE.03:05.01:01.01”


Same as yours.

If anybody is interessted, here is a blogpost about my finished project:

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