weewx-sdr
Copyright 2016-2024 Matthew Wall
Distributed under terms of the GPLv3

This is a driver for weewx that captures data from software-defined radio.
It works with open source rtl sdr software that in turn works with
inexpensive, broad spectrum radio receivers such as the Realtek RTL2838UHIDIR.
These devices cost about 20$US and are capable of receiving radio signals from
weather stations, energy monitors, doorbells, and many other devices that use
unlicensed spectrum such as 433MHz, 838MHz, and 900MHz frequencies.


===============================================================================
Hardware

Tested with the Realtek RTL2838UHIDIR.  Should work with any software-defined
radio that is compatible with the rtl-sdr software.  Uses the modules in
rtl_433 to recognize packets.

Output from many different sensors is supported.  To see the list of supported
sensors, run the driver directly with the list-supported action.

If a sensor is supported by rtl_433 but not by weewx-sdr, it is a fairly simple
matter of writing a parser for that sensor within weewx-sdr.  Things are a bit
more complicated if a sensor is not supported by rtl_433.


===============================================================================
Installation

0) install pre-requisites

  a) install weewx
      http://weewx.com/docs
  b) install rtl-sdr
      http://sdr.osmocom.org/trac/wiki/rtl-sdr
  c) install rtl_433
      https://github.com/merbanan/rtl_433

1) install the driver

weectl extension install https://github.com/matthewwall/weewx-sdr/archive/master.zip

2) configure the driver

weectl station reconfigure --driver=user.sdr --no-prompt

3) run the driver directly to identify the packets you want to capture

export WEEWX_BINDIR=/usr/share/weewx
export WEEWX_USRDIR=/etc/weewx/bin/user
PYTHONPATH=$WEEWX_BINDIR python3 $WEEWX_USRDIR/sdr.py --cmd="rtl_433 -M utc -F json"

4) modify the [SDR] section of weewx.conf using a text editor

- create a [[sensor_map]] for the data you want to capture
- possibly modify the 'cmd' parameter

5) start weewx

sudo systemctl start weewx


===============================================================================
How to run the driver directly

You can run the driver directly for testing, diagnostics, and development.  In
fact, you can run the driver without installing it - just invoke python on it!
In the examples elsewhere in this file, you will see this illustrated with the
generic form, which is:

  python3 sdr.py

However, in most cases you must specify the location of the WeeWX modules using
PYTHONPATH.  So that generic form will become something like this:

  PYTHONPATH=/path/to/weewx/modules python3 sdr.py

For example, a deb/rpm installation would look like this:

  PYTHONPATH=/usr/share/weewx python3 /etc/weewx/bin/user/sdr.py

A pip/venv installation would look something like this:

  PYTHONPATH=~/weewx-env python3 ~/weewx-data/bin/user/sdr.py

Note:
You might have use 'sudo' if the user does not have permission to read/write
the USB SDR device.


===============================================================================
Configuration - the sensor_map

Use the [SDR] section of the weewx configuration file (nominally weewx.conf) to
adjust the driver configuration.

The rtl_433 executable emits data for many different types of sensors, some of
which have similar output.  Use the sensor_map to distinguish between sensors
and map the output from rtl_433 to the database fields in weewx.

To identify sensors, run the driver directly.  If you do not yet have a sensor
map, then use the default invocation so that you can see all of the sensors
that rtl_433 recognizes.  From this output you will choose the sensors and
their identifiers to create your sensor_map.

  python3 sdr.py

Here are some sensor_map examples:

# collect data from Acurite 5n1 sensor 0BFA and t/h sensor 24A4
[SDR]
    driver = user.sdr
    [[sensor_map]]
        windDir = wind_dir.0BFA.Acurite5n1Packet
        windSpeed = wind_speed.0BFA.Acurite5n1Packet
        outTemp = temperature.0BFA.Acurite5n1Packet
        outHumidity = humidity.0BFA.Acurite5n1Packet
        rain_total = rain_total.0BFA.Acurite5n1Packet
        inTemp = temperature.24A4.AcuriteTowerPacket
        inHumidity = humidity.24A4.AcuriteTowerPacket

# collect data from Acurite 986 fridge/freezer sensor set 1R and 2F
[SDR]
    driver = user.sdr
    [[sensor_map]]
        extraTemp1 = temperature.1R.Acurite986Packet
        extraTemp2 = temperature.2F.Acurite986Packet

# collect data from Acurite 06002RM t/h sensor 3067
[SDR]
    driver = user.sdr
    [[sensor_map]]
        inTemp = temperature.3067.AcuriteTowerPacket
        inHumidity = humidity.3067.AcuriteTowerPacket

# collect data from two Hideki TS04 sensors with channel=1 and channel=2
[SDR]
    driver = user.sdr
    [[sensor_map]]
        outBatteryStatus = battery.1:9.HidekiTS04Packet
        outHumidity = humidity.1:9.HidekiTS04Packet
        outTemp = temperature.1:9.HidekiTS04Packet
        inBatteryStatus = battery.2:9.HidekiTS04Packet
        inHumidity = humidity.2:9.HidekiTS04Packet
        inTemp = temperature.2:9.HidekiTS04Packet

# collect data from Fine Offset sensor cluster with serial number 0026
[SDR]
    driver = user.sdr
    [[sensor_map]]
        windGust = wind_gust.0026.FOWH1080Packet
        outBatteryStatus = battery.0026.FOWH1080Packet
        rain_total = rain_total.0026.FOWH1080Packet
        windSpeed = wind_speed.0026.FOWH1080Packet
        windDir = wind_dir.0026.FOWH1080Packet
        outHumidity = humidity.0026.FOWH1080Packet
        outTemp = temperature.0026.FOWH1080Packet


===============================================================================
Configuration - options to rtl_433

The default configuration uses this command:

rtl_433 -M utc -F json

Specify different options using the cmd parameter.  For example:

[SDR]
    driver = user.sdr
    cmd = rtl_433 -M utc -F json -R 17 -R 44 -R 50


===============================================================================
Configuration - logging

If you turn on debug=1, you will see a bewildering output from the SDR driver.
Although this is really helpful when debugging and diagnosing problems, often
you want far less information.  There are a few logging options to help you
control this beast.

[SDR]
    driver = user.sdr
    log_lines = (True | False)
    log_unknown_sensors = (True | False)
    log_unmapped_sensors = (True | False)
    log_packets = (True | False)             # only applies with debug=1
    log_duplicate_readings = (True | False)  # only applies with debug=1


===============================================================================
Configuration - cumulative observations - the 'deltas' section

Some sensors report a current value, e.g., temperature or humidity, whereas
other report a cumulative total, e.g., rain.  The 'deltas' section indicates
how to map a cumulative total to a per-period amount.

The default deltas knows about rain and lightning strikes, and it assumes that
the 'rain_total' and 'strikes_total' are total counts that must be mapped to
the per-period variables 'rain' and 'lightning_strike_count'.  It is specified
as follows:

[SDR]
    ...
    [[sensor_map]]
        rain_total = rain_mm.0026.FOWH1080Packet
        ...
    [[deltas]]
        rain = rain_total
        lightning_strike_count = strikes_total

What is going on here?  Let's say that rtl_433 reports sensor output for rain
as 'rain_mm', a cumulative count of rainfall.  The sensor map puts the value
from 'rain_mm' into 'rain_total', then a function _calculate_deltas uses the
definition in [[deltas]] to break rain_total down to only the amount since the
last rain_total was reported.

All of this keeps WeeWX happy - it expects an observation 'rain' that is the
amount of rainfall in the current period, whether that is loop or archive.


===============================================================================
Configuration - detecting new sensors

After you have run for awhile, you might want to add new sensors to your
system.  If you have more than two or three sensors, it can be quite a
challenge to pick through all of the output when you run the driver directly.
This shows how to display only sensors that are detected but not yet part of
your weewx configuration.

First, shut down weewx so that you can talk to the SDR directly.

Then run the SDR driver directly, but tell it to print out information only
about sensors that you have not yet added to your weewx configuration:

  python3 sdr.py --config weewx.conf --hide=out,parsed,mapped

As always, unless the sensor identifier is marked on the sensor itself, you
should turn on sensors one at a time, marking the outside of the sensor with
its identifier.  Then you can turn on all the sensors and place them, using
the identifier on the sensor to distinguish which sensor is which when you
map them to database fields in your weewx configuration.


===============================================================================
How to diagnose problems

First try running the rtl_433 application to be sure that it works properly:

sudo rtl_433

Be sure that you are capturing data from the sensors you care about.  To do
this, you might want to experiment with some of the options to rtl_433.  For
example, this will eliminate extraneous output (-q), and use UTC for timestamps
(-M utc):

sudo rtl_433 -M utc -F json

If you know exactly which sensors you want to monitor, try the -R option to
reduce the clutter.  For example,

sudo rtl_433 -M utc -F json -R 9 -R 31

Once that is working, run the driver directly to be sure that it is collecting
data from the rtl_433 application.

python3 sdr.py --cmd="rtl_433 -M utc -F json"

Make note of the sensor identifiers.  Each identifier is a three-part string
consisting of the observation, sensor id, and rf packet type, separated by
periods.  You need these in the sensor map to tell weewx the association
between sensors and database fields.

In the weewx configuration file, enter the rtl_433 options (if necessary) and
the sensor map.  Then run weewx directly in one shell while you monitor the
weewx log in a separate shell:

in shell 1:
cd /home/weewx
sudo ./bin/weewxd weewx.conf

in shell 2:
tail -f /var/log/syslog

At this point, verify that the mapping you made in the weewx configuration file
is working as you intend.  You should see data from your sensors in the weewx
LOOP and REC output.  If not, check the log file.  Use the logging options in
the [SDR] section of the weewx configuration file to help figure out which
sensors are captured, recognized, and parsed.

Once you are satisfied with the output when running weewx directly, run weewx
as a daemon and configure rc script or systemd to run weewx at system startup.

sudo systemctl start weewx


===============================================================================
Environment

The driver invokes the rtl_433 executable, so the path to that executable and
any shared library linkage must be defined in the environment in which weewx
runs.

For example, with rtl_433 and rtl-sdr installed like this:

/opt/rtl-433/
/opt/rtl-sdr/

one would set the path like this:

export PATH=/opt/rtl-433/bin:${PATH}
export LD_LIBRARY_PATH=/opt/rtl-sdr/lib

Typically this would be done in the rc script that starts weewx.  If rtl_433
and rtl-sdr are install to /usr/local or /usr, then there should be no need
to set the PATH or LD_LIBRARY_PATH before invoking weewx.

If you cannot control the environment in which weewx runs, then you can specify
the LD_LIBRARY_PATH and PATH in the weewx-sdr driver itself.  For example:

[SDR]
    driver = user.sdr
    cmd = rlt_433 -M utc -F json
    path = /opt/rtl-433/bin
    ld_library_path = /opt/libusb-1.0.20/lib:/opt/rtl-sdr/lib
    [[sensor_map]]
        ...


===============================================================================
libusb

I have had problems running rtl-sdr on systems with libusb 1.0.11.  The rtl_433
command craps out with a segmentation fault, and the rtl_test command sometimes
leaves the dongle in a weird state that can be cleared only by unplugging then
replugging the dongle.

Using a more recent version of libusb (e.g., 1.0.20) seems to clear things up.


===============================================================================
Support for new sensor types

To add support for new sensors, capture the output from rtl_433.  To capture
output, run the driver directly and hide known packets:

  python3 sdr.py --cmd="rtl_433 -M utc -F json" --hide parsed,out,empty

This should emit a line for each unparsed type.  For example:

unparsed: ['{"time" : "2017-01-16 15:44:51", "temperature" : 54.140, "humidity" : 34, "id" : 221, "model" : "LaCrosse TX141TH-Bv2 sensor", "battery" : "OK", "test" : "Yes"}\n']

If there is no json ouput, remove the '-F json' option to see the (deprecated)
non-json output:

unparsed: ['2016-11-04 16:12:39 :\tFine Offset Electronics, WH2 Temperature/Humidity sensor\n', '\tID:\t 38\n', '\tTemperature:\t 54.4 C\n', '\tHumidity:\t 55 %\n']

If you are not comfortable writing your own parser, post the output to the
issues section of the weewx-sdr repository and some helpful person might write
the parser for you.


===============================================================================
Historical notes

When this driver was first created, most of the output from rtl_433 was only
available as multi-line plain text, often but not always with some structure.
JSON output was soon introduced, but there were many inconsistencies between
sensors and rtl_433 releases.  Thankfully this stabilized over time.

The driver includes two parsing methods: parse_text and parse_json.  The former
is deprecated, and although many other formats have been added to rtl_433, only
the json format is supported (and encouraged) in this driver.

There have been other changes as well, such as the syntax for specifying the
time - it went from "-M utc" to "-M time:iso".  At some point we might want to
use "-M time:unix" so that we don't have to do the pattern match for time
strings.  Or not.

I've tried to maintain backward compatibility, but the early days had so many
variations of sensor output and rtl_433 output, so that is not really feasible.