Purpose

Utilities often use "smart meters" to optimize their residential meter reading infrastructure. Smart meters transmit consumption information in the 900MHz ISM band allowing utilities to simply send readers driving through neighborhoods to collect commodity consumption information. One protocol in particular: Encoder Receiver Transmitter by Itron is fairly straight forward to decode, however I have yet to find any reasonably priced product for receiving these messages.

This project is a software defined radio receiver for these messages. We make use of an inexpensive rtl-sdr dongle to allow users to non-invasively record and analyze the commodity consumption of their household.

Requirements

• GoLang >=1.2 (Go build environment setup guide: http://golang.org/doc/code.html)
• rtl-sdr
  • Windows: pre-built binaries
  • Linux: source and build instructions

Building

This project requires the package github.com/bemasher/rtltcp, which provides a means of controlling and sampling from rtl-sdr dongles via the rtl_tcp tool. This package will be automatically downloaded and installed when getting rtlamr. The following command should be all that is required to install rtlamr.

go get github.com/bemasher/rtlamr

This will produce the binary $GOPATH/bin/rtlamr. For convenience it's common to add $GOPATH/bin to the path.

Usage

Available command-line flags are as follows:

Usage of rtlamr:
  -cpuprofile=: write cpu profile to this file
  -duration=0: time to run for, 0 for infinite, ex. 1h5m10s
  -fastmag=false: use faster alpha max + beta min magnitude approximation
  -filterid=0: display only messages matching given id
  -filtertype=0: display only messages matching given type
  -format=plain: format to write log messages in: plain, csv, json, xml or gob
  -gobunsafe=false: allow gob output to stdout
  -logfile=/dev/stdout: log statement dump file
  -msgtype=scm: message type to receive: scm or idm
  -quiet=false: suppress printing state information at startup
  -samplefile=/dev/null: raw signal dump file
  -single=false: one shot execution
  -symbollength=73: symbol length in samples, see -help for valid lengths

rtltcp specific:
  -agcmode=false: enable/disable rtl agc
  -centerfreq=920299072: center frequency to receive on
  -directsampling=false: enable/disable direct sampling
  -freqcorrection=0: frequency correction in ppm
  -gainbyindex=0: set gain by index
  -offsettuning=false: enable/disable offset tuning
  -rtlxtalfreq=0: set rtl xtal frequency
  -samplerate=2400000: sample rate
  -server=127.0.0.1:1234: address or hostname of rtl_tcp instance
  -testmode=false: enable/disable test mode
  -tunergain=0: set tuner gain in dB
  -tunergainmode=false: enable/disable tuner gain
  -tunerxtalfreq=0: set tuner xtal frequency

Running the receiver is as simple as starting an rtl_tcp instance and then starting the receiver:

# Terminal A
$ rtl_tcp

# Terminal B
$ rtlamr

If you want to run the spectrum server on a different machine than the receiver you'll want to specify an address to listen on that is accessible from the machine rtlamr will run on with the -a option for rtl_tcp with an address accessible by the system running the receiver.

Messages

Currently both SCM (Standard Consumption Message) and IDM (Interval Data Message) packets can be decoded but are mutually exclusive, you cannot receive both simultaneously. See Wikipedia: Encoder Receiver Transmitter for more details on packet structure.

Sensitivity

Using a NooElec NESDR Nano R820T with the provided antenna, I can reliably receive standard consumption messages from ~250 different meters and intermittently from another 400 meters. These figures are calculated from messages received during a 25 minute window where the preamble had no bit errors and no errors were detected or corrected using the checksum. Reliably in this case means receiving at least 10 of the expected 12 messages and intermittently means 3-9 messages.

Compatibility

Currently the only tested meter is the Itron C1SR. However, the protocol is designed to be useful for several different commodities and should be capable of receiving messages from any ERT capable smart meter.

Check out the table of meters I've been compiling from various internet sources: ERT Compatible Meters

If you've got a meter not on the list that you've successfully received messages from, you can submit this info via a form available at the link above.

Ethics

Do not use this for nefarious purposes. If you do, I don't want to know about it, I am not and will not be responsible for your lack of common decency and/or foresight. However, if you find a clever non-evil use for this, by all means, share.

License

The source of this project is licensed under Affero GPL. According to http://choosealicense.com/licenses/agpl/ you may:

Required:

• Source code must be made available when distributing the software. In the case of LGPL, the source for the library (and not the entire program) must be made available.
• Include a copy of the license and copyright notice with the code.
• Indicate significant changes made to the code.

Permitted:

• This software and derivatives may be used for commercial purposes.
• You may distribute this software.
• This software may be modified.
• You may use and modify the software without distributing it.

Forbidden:

• Software is provided without warranty and the software author/license owner cannot be held liable for damages.
• You may not grant a sublicense to modify and distribute this software to third parties not included in the license.

Feedback

If you have any general questions or feedback leave a comment below. For bugs, feature suggestions and anything directly relating to the program itself, submit an issue in github.