rtl_433 ERT SCM protocol - simulation

[Rafal Pospieski]

Gents,
I`m trying to simulate ert scm protocol to be able to read data using SDR+rtl_433.
I do not have any meter of such kind to track exact frame.
I need to make the frame to be read using standard protocol which is part of rtl_433 library.
All data which I have is a few pages on the internet as:

https://github.com/merbanan/rtl_433/blob/master/src/devices/ert_scm.c
https://github.com/bemasher/rtlamr/blob/master/scm/scm.go
https://la.mathworks.com/help/comm/ug/automatic-meter-reading.html
crccalc.com

as I understand I need to send data using for example cc1120 with config:
See cc1120config.png

The data which I send must be something like:

Binary Hex
111110010101001100000000 F95300
00 010000 10    
000100010001000100010001 111111
000100010001000100010001 111111
checksum d4 13

The RF frame which I send for sure is: (picked up by SDR+rtl_433+PulseView)

see ert_scm.png file

So for me it looks promising (all data which I wanted to be send are send) but unfortunatelly rtl_433 does not read it when I use:
rtl_433 -f 915M -s 1200k

One thing that I`m not sure about is how to calculate the checksum of the data and exacly on what bytes?
Currently I`m calculating the checksum based on all above bytes using  crc-16 /LJ1200 agorithm mentioned in documentation I`ve found.

What I`m doing wrong or maybe somebody could pass me a sample frame which would be picked up by rtl_433?

best regards

Rafal

[Benjamin Larsson]

On 07/08/2025 14:59, Rafal Pospieski wrote:
> Gents,
> I`m trying to simulate ert scm protocol to be able to read data using
> SDR+rtl_433.
> I do not have any meter of such kind to track exact frame.
> I need to make the frame to be read using standard protocol which is
> part of rtl_433 library.
> All data which I have is a few pages on the internet as:
>
> https://github.com/merbanan/rtl_433/blob/master/src/devices/ert_scm.c
> https://github.com/bemasher/rtlamr/blob/master/scm/scm.go
> https://la.mathworks.com/help/comm/ug/automatic-meter-reading.html
> crccalc.com
>
> as I understand I need to send data using for example cc1120 with config:
> See cc1120config.png
>
> The data which I send must be something like:
>
> BinaryHex
> 111110010101001100000000 F95300
> 00 01000010
> 000100010001000100010001111111
> 000100010001000100010001111111

> checksumd4 13

>
> The RF frame which I send for sure is: (picked up by SDR+rtl_433+PulseView)
>
> see ert_scm.png file
>
> So for me it looks promising (all data which I wanted to be send are
> send) but unfortunatelly rtl_433 does not read it when I use:
> rtl_433 -f 915M -s 1200k
>
> One thing that I`m not sure about is how to calculate the checksum of
> the data and exacly on what bytes?
> Currently I`m calculating the checksum based on all above bytes using
>  crc-16 /LJ1200 agorithm mentioned in documentation I`ve found.
>
> What I`m doing wrong or maybe somebody could pass me a sample frame
> which would be picked up by rtl_433?
>
> best regards
> Rafal
>

What happens if you increase the rtl_433 verbosity and only enable the
relevant protocol?

Here are some test files:

https://github.com/merbanan/rtl_433_tests/blob/master/tests/scmplus/README.md

You can also use -y to test your generated bitstreams. Play around with
these files and options and you should be able to get it working. Don't
be afraid to add some debug lines to the decoder also.

MvH
Benjamin Larsson

[Rafal Pospieski]

Benjamin,

Than You so much for Your support. I`m working on it almost two weeks (+ setting up CC1120 and STM32) already and I`m stuck with it right now. I would like to use ERT SCM to pass data to Home Assistant from my energy counters (home made) so I need to use protocols as in rtl_433 library since it is hooked up to my Home Assistant as plugin.

Thank You for pointing me out these test files.These are helpful!. 

The issue is that with my rtl_433 version SCM plus file/protocol is read correctly from file but ERT SCM is not recognized in the file.

The file which is not working (my rtl_433 is not able to detect any protocol) is:

https://github.com/merbanan/rtl_433_tests/blob/master/tests/ert/scm/01/g001_912.6M_2.4M.cu8

when I call :

rtl_433 -f 912.6M -s 1200k -r g001_912.6M_2.4M.cu8

I get:

rtl_433 version -128-NOTFOUND branch  at 202503301205 inputs file rtl_tcp RTL-SDR SoapySDR

New defaults active, use "-Y classic -s 250k" if you need the old defaults

[Input] Test mode active. Reading samples from file: g001_912.6M_2.4M.cu8

Nothing more....

When I use it on the file You have pointed me I get:

when I call:

rtl_433 -f 912.6M -s 1200k -r g002_912.6M_2359.3k.cu8

rtl_433 version -128-NOTFOUND branch  at 202503301205 inputs file rtl_tcp RTL-SDR SoapySDR

New defaults active, use "-Y classic -s 250k" if you need the old defaults

[Input] Test mode active. Reading samples from file: g002_912.6M_2359.3k.cu8
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
time      : @0.045207s
model     : SCMplus      id        : 68211547
Protocol_ID: 0x1E        Endpoint_Type: 0xAB       Endpoint_ID: 68211547     Consumption: 6883
Tamper    : 0x4900       crc       : 0x39BE        Meter_Type: Water         Integrity : CRC

So it looks like rtl_433 is reading SCMplus but not ERT SCM.

I really would like to use ERT SCM because it is a lot easier for me to generate the frame and I`m struggling with SCMplus...

Would You be able to help me?

best regards

Rafal

[Benjamin Larsson]

On 08/08/2025 10:53, Rafal Pospieski wrote:
> Benjamin,
> Than You so much for Your support. I`m working on it almost two weeks (+
> setting up CC1120 and STM32) already and I`m stuck with it right now. I
> would like to use ERT SCM to pass data to Home Assistant from my energy
> counters (home made) so I need to use protocols as in rtl_433 library
> since it is hooked up to my Home Assistant as plugin.
>
> Thank You for pointing me out these test files.These are helpful!.
> The issue is that with my rtl_433 version SCM plus file/protocol is read
> correctly from file but ERT SCM is not recognized in the file.
>
> The file which is not working (my rtl_433 is not able to detect any
> protocol) is:
> https://github.com/merbanan/rtl_433_tests/blob/master/tests/ert/scm/01/g001_912.6M_2.4M.cu8
>
> when I call :
> rtl_433 -f 912.6M -s 1200k -r g001_912.6M_2.4M.cu8
>
> I get:
> rtl_433 version -128-NOTFOUND branch  at 202503301205 inputs file
> rtl_tcp RTL-SDR SoapySDR
>
> New defaults active, use "-Y classic -s 250k" if you need the old defaults
>
> [Input] Test mode active. Reading samples from file: g001_912.6M_2.4M.cu8
>
> Nothing more....
>

rtl_433 -s 2400k -r g001_912.6M_2.4M.cu8

Test mode active. Reading samples from file: g001_912.6M_2.4M.cu8

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

time : @0.048215s
model : ERT-SCM Id : 54585868
Physical Tamper: 3 ERT Type : 12 Encoder Tamper: 0
Consumption Data: 562456 Integrity : CRC


MvH
Benjamin Larsson

[Rafal Pospieski]

It is working now! Even on SCMPlus !!!! See picture.

Just one more question. 

Now its working on 915 Mhz. I have hardware for that frequency. Do You know maybe if I switch to 433Mhz hardware,  would rtl_433 be able to pick it up as well on regular settings/library?

best regards

Rafał

[Benjamin Larsson]

On 08/08/2025 13:31, Rafal Pospieski wrote:
> It is working now! Even on SCMPlus !!!! See picture.
>
> Just one more question.
>
> Now its working on 915 Mhz. I have hardware for that frequency. Do You
> know maybe if I switch to 433Mhz hardware,  would rtl_433 be able to
> pick it up as well on regular settings/library?
>
> best regards
> Rafał

It should work. Make sure you stay within legal transmission limits though.

MvH
Benjamin Larsson