January 2021
Some notes on how I set up a weather station on a Raspberry Pi zero W using Weewxsoftware, SDR (a software defined radio USB dongle), an Oregon WMR89 and a Bresser 5in1 weather station. The Oregon unit transmits on 433Mhz and is fairly standard. The Bresser unit is newer and, as a result of recent charges in their protocol needs a bit more hacking to get it working.
Antenna lengths
The usb dongle is supplied with a short whip aerial. Its not very critical, but if you need max range, here is the theory.
1/4 wave dipole best when there is an earth plane. 1/2 wave is better when there is no earth plane. Figures below dont take account of speed of light in a wire is less than in a vacuum but none of it is critical.
433Mhz - 173mm for a 1/4 wave whip
868Mhz - 86.3mm
Installation
These notes cover both the Oregon WMR89 sensors and the new version Bresser 5-in-1 weather station.
Follow these instructions to install the modules on the RPi.
https://github.com/weewx/weewx/wiki/sdr-rpi-recipe
https://github.com/weewx/weewx/wiki/sdr-rpi-recipe.
If using the Bresser sensors, make sure you install rtl_433 version 20.11 or later. Earlier versions may not parse Bresser 5in1 correctly. Most recent will handle the Oregon.
Testing rtl_433
Check radio signals being recieved and parsed by rtl_433. For the Bresser station you will need to to specify the frequency on the command line as operates at 868.2Mhz rather than the default 433Mhz for the OregonScientific. Note not all packets include temperature and humidity so be sure to examine a few!
sudo rtl_433 -F json -f 868.2M -s 1M
.....{"time" : "2021-01-15 16:14:34", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "rain_mm" : 6.400, "mic" : "CRC"}
{"time" : "2021-01-15 16:14:46", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "temperature_C" : 1.300, "humidity" : 87, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "mic" : "CRC"}
{"time" : "2021-01-15 16:14:58", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "rain_mm" : 6.400, "mic" : "CRC"}
{"time" : "2021-01-15 16:15:10", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "temperature_C" : 1.300, "humidity" : 87, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "mic" : "CRC"}
Modify sdr.py for Bresser
The current version of /usr/share/weewx/user/sdr.py includes code to parse the Oregon WMR89 weather station, but not the current version of the Bresser n-in1. You need to add a class to parse the output and also add it to the list of data types in class PacketFactory(). Its very similar to the Bresser 5-in-1. If you cut and paste the code you will need to tidy up the tabs and indentation.
class Bresser6in1Packet(Packet):
# Includes newer versions of 5 in 1 as well as 6 in 1 and 7 in 1.
#{"time" : "2021-01-15 16:14:58", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "rain_mm" : 6.400, "mic" : "CRC"}
#{"time" : "2021-01-15 16:15:10", "model" : "Bresser-6in1", "id" : 541070586, "channel" : 0, "battery_ok" : 1, "temperature_C" : 1.300, "humidity" : 87, "sensor_type" : 1, "wind_max_m_s" : 0.000, "wind_avg_m_s" : 0.000, "wind_dir_deg" : 270, "mic" : "CRC"}
IDENTIFIER = "Bresser-6in1"
@staticmethod
def parse_json(obj):
pkt = dict()
pkt['dateTime'] = Packet.parse_time(obj.get('time'))
pkt['usUnits'] = weewx.METRICWX
pkt['station_id'] = obj.get('id')
pkt['channel'] = obj.get('channel')
pkt['battery'] = obj.get('battery_ok')
pkt['sensor_type'] = obj.get('sensor_type')
# deal with different labels from rtl_433
for dst, src in [('temperature_C', 'temperature_C'),
('humidity','humidity'),
('moisture','moisture'),
('wind_speed', 'wind_avg_m_s'),
('gust_speed', 'wind_max_m_s'),
('wind_dir_deg','wind_dir_deg'),
('rain_total', 'rainfall_mm'),
('rain_total', 'rain_mm'),
('uv','uv')]:
if src in obj:
pkt[dst] = Packet.get_float(obj,src)
return Bresser6in1Packet.insert_ids(pkt)
@staticmethod
def insert_ids(pkt):
station_id = pkt.pop('station_id', '0000')
pkt = Packet.add_identifiers(pkt, station_id, Bresser6in1Packet.__name__)
return pkt
class PacketFactory(object):
KNOWN_PACKETS = [
AcuriteAtlasPacket,
...
Bresser6in1Packet,
...
Testing sdr.py
Your command line to test sdr.py with the Bresser station at the will look like:
sudo PYTHONPATH=/usr/share/weewx python3 /usr/share/weewx/user/sdr.py --cmd="rtl_433 -M utc -F json -f 868M"
The output will look something like this:
out:['{
"time" : "2021-01-17 11:48:15",
"model" : "Bresser-6in1",
"id" : 541070586,
"channel" : 0,
"battery_ok" : 1,
"temperature_C" : 7.100,
"humidity" : 69,
"sensor_type" : 1,
"wind_max_m_s" : 3.000,
"wind_avg_m_s" : 2.900,
"wind_dir_deg" : 270,
"mic" : "CRC"
}\n']
parsed: {
'dateTime': 1610884095, 'usUnits': 17,
'battery.541070586.Bresser6in1Packet': 1,
'temperature_C.541070586.Bresser6in1Packet': 7.1,
'humidity.541070586.Bresser6in1Packet': 69.0,
'wind_speed.541070586.Bresser6in1Packet': 2.9,
'gust_speed.541070586.Bresser6in1Packet': 3.0,
'wind_dir_deg.541070586.Bresser6in1Packet': 270.0
}
You can now edit weewx.conf to suit. Its located in
/etc/weewx/weewx.conf
Here is my section for SDR. Commands for the Oregon WMR89 are commented out.
[SDR]
# This section is for the software-defined radio driver.
# The driver to use
driver = user.sdr
#cmd = rtl_433 -M utc -F json
cmd = rtl_433 -M utc -F json -f868.2M
path = /usr/local/bin/
log_unknown_sensors = True
log_unmapped_sensors = True
[[sensor_map]]
# Oregon WMR89
# windSpeed = wind_speed.0:215.OSWGR800Packet
# windGust = wind_gust.0:215.OSWGR800Packet
# windDir = wind_dir.0:215.OSWGR800Packet
# windBatteryStatus = battery.0:215.OSWGR800Packet
# outTemp = temperature.1:246.OSTHGR810Packet
# outHumidity = humidity.1:246.OSTHGR810Packet
# outTempBatteryStatus = battery.1:246.OSTHGR810Packet
# pressure = pressure.1:246.OSTHGR810Packet
# rainBatteryStatus = battery.0:122.OSPCR800Packet
# rainRate = rain_rate.0:122.OSPCR800Packet
# rain_total = rain.0:122.OSPCR800Packet
# Bresser 5in1 (new format)
windSpeed = wind_speed.541070586.Bresser6in1Packet
windGust = gust_speed.541070586.Bresser6in1Packet
windDir = wind_dir_deg.541070586.Bresser6in1Packet
outTemp = temperature_C.541070586.Bresser6in1Packet
outHumidity = humidity.541070586.Bresser6in1Packet
pressure = pressure.541070586.Bresser6in1Packet
[[deltas]]
rain = rain_total
Finishing Up
Finally, the default web page does not autorefresh. To make it easier to reload the page I made the station name in the masthead into a link to auto refresh script. Its like old school tapping a barometer to see if the pressure is falling. Although a lot can be configured through weewx.conf, this change has to be made in the skin. The default is located in /etc/weewx/skins/Seasons. The page index.html.tmpl calls titlebar.inc to build the masthead. Wrapping a <a> element with some javascript around the relevant div gives the wanted effect:
....
<div id="title_bar">
<a HREF="javascript:history.go(0)">
<div id="title">
<h1 class="page_title">$station.location</h1>
<p class="lastupdate">$current.dateTime</p>
</div>
</a>
....
