Radio weatherstations in the UNIX environment
It is described howto interface low-cost radio weatherstations to the
serial port in
a Free Software environment. These radio weatherstations are sold as
PC radio receivers plus external sensors by mailorder ELV or CONRAD.
Further description of
the weatherstations is given in the hardware section.
Several types of environment sensors like temperature, humidity, air pressure,
wind, rainfall or brightness transmit data to a radio receiver where it can be
retrieved to a computer over the serial link. Depending on the type of
receiver the communication with the computing equipment is either
unidirectional or bidirectional.
In the unidirectional case data is written to the serial line directly upon
reception. The bidirectional stations use internal memory to store data which
can be retrieved by issuing commands to the serialline.
The communication software has been written and tested for the LINUX
and FreeBSD operating systems.
The wth project is hosted by Berlios.
The WS2000 weatherstations
The actual WS2000 weatherstation is a radio weatherstation available
from the German electronic reseller ELV by
mailorder.
The Profi Wetterstation
weatherstation by CONRAD uses the same
communication protocol as the WS2000 station. Both sensors and receivers of
these two stations operate
with each other flawlessly. The weatherstation sensors communicate wireless
to a radio receiver which can be read by a computer over the serial link.
The wireless link transmits data at 433.92 MHz with extrem low power
(approximately 10mW).
WS2000 PC receiver
The PC receivers are either
| bidirectional with integrated DCF77 time receiver,
ring buffer for data storage (32kB) and serial interface |
 |
| unidirectional without internal memory for serial connection. This
unit is sold as a kit only |
 |
The receivers are connected thru a standard RS232 serial line with the
computing equipment. Where the bidirectional unit is battery powered
(4 AA batteries, haven't been replaced within one year of operation) the
unidirectional receiver is powered by 5V DC which is taken by connecting
to the PC power supply.
WS2000 sensors
The sensors include radio transmitters to send the weather data. The radiation
power of these sensors is extremely low (10mW per sensor).
| combined temperature, humidity (and air pressure) sensor
for indoor use |
 |
combined temperature, humidity sensor for outdoor
use |
 |
| wind sensor |
| rainfall sensor
|  |
| brightness sensor (supported only by unidirectional receiver)
|  |
It is possible to install up to 16 temperature/humidity sensors, 1 wind sensor
and 1 rainfall sensor. The brightness sensor is only supported by the
unidirectional receiver.
The sensors have approximately 100m reach which can be extended by repeaters.
They operate independently using a integrated solar module. The sensors are
detected automagically by the receivers at power on.
For the software development a WS7000-13 bidirectional receiver by CONRAD,
a WS2000 bidirectional receiver by ELV and the unidirectional
PC weathersensor receiver by ELV have been used. All sensors but the brightness
sensor have been tested.
The weatherstation modules are available as a set or in parts thru mailorder
electronic resellers like ELV or
CONRAD.
Serial communication protocol
It seems appropriate to categorize the serial weatherstations mainly into
two types according to their coomunication behaviour with the computing
equipment. While the first type uses a bidirectional serial communication
protocol the other type operates in an unidirectional manner.
Bidirectional communication
One type communicates with the computing equipment in a bidirectional mannner
ie. data is sent to the computer only upon request. This could be depicted in
ASCII art like:
request
Computer -> PC-Interface
response
<-
|
It is the WS2000 weatherstations by ELV or CONRAD which work in this way.
These stations use a high-level communication protocol which even uses
checksums for data correction.
There is also another type of stations which use an extra piece of hardware
to connect to the weatherstation.
The Davis weatherstations operate by bidirectional serial line communication
with the WeatherLink, a piece of hardware which allows fast data transfer
off the weatherstation. The WeatherLink is connected in between the computer
and the weatherstation. Data in the weatherstatoin itself can also be accessed.
request request
Computer -> Weather -> Weather Station
response Link response
<- <-
|
Unidirectional operation
The other type of weatherstations operates unidirectional, ie. data
is sent continuously or in certian periods to the serial line. The data
typically consist of packets having a defined format.
Computer receives PC-Interface
<-
data
|
At present time the protocol of the following stations has been
reproduced in a compilation at
http://thalreit.de/attic/project/station-protocol.txt
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ELV/Conrad WS2000 PC-Interface
|
|
ELV PC Weather Sensor Receiver
|
|
Huger WMR918
|
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Radioshack WX200
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Davis weatherstations
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It is emphasized, that this compilation does not include
any new work what serial
protocol analyzing is concerned, but is rather a collection of information
available either on the internet or in other forms of publication. It should
be noted however that for the communication protocol of the ELV PC
weathersensor receiver a serial line
snooper has been used for test purposes. It includes a little howto use
the snooper tool
for serial line snooping.
Software
At present time two modules are available which support the WS2000 type
weatherstation receiver and the ELV PC weathersensor receiver,
wth and
pcwsr.
The project homepage is hosted by
the
berlios project.
Implementation
The wthc software is a full implementation of communication
protocol of the wireless weatherstation. The client program
is able to communicate either with a locally attached
weatherstation or with a network service, which runs on
another station with a locally attached weatherstation. The
network service has been implemented as tcp server and must
run on the remote machine in order for the client software
to be able to connect. The data exchange with the client
software is done with the same protocol which is used over
the serial line. The tcp server is able to communicate with
the serially attached weatherstation and then sends its data
to the client software. Otherwise the tcpserver offers a
telnet service with full functionality. The communication
port with the client software is on port 3900, whereas
telnet access is on port 3901.
Usage
This section contains manual pages for the client software
wthc and the tcp server wthd.
wthc
wthc - control serial/network interface of weatherstation
SYNOPSIS
wthc [ -c command ] [ -s | -n ] [ -h hostname ] [ -i
intervall ] [ -p portnumber]
DESCRIPTION
wthc controls the serial or network interface to a weath-
erstation module. It is possible to read data like tem-
perature, humidity, air pressure, wind speed, wind direc-
tion and rain fall. The DCF77 receiver can be read as well
as current status information. If the module is connected
by a serial line, data is read directly from a 64kB ring
buffer. For network access a server process must run on
the system where the weatherstation module is locally
attached.
OPTIONS
- -c command
- specifies the command to be executed, where command
can take values as described in section COMMAND
PARAMETERS.
- -h hostname
- hostname or IP address to connect to remote server,
in case weatherstation is not locally connected to
serial port.
- -i intervall
- intervall time of data sets collected by weather-
station. This option is only needed in conjunction
with command 6.
- -p portnumber
- use portnumber to connect to remote server, default
is 3963.
- -s
- use local serial connection for readout
- -n
- use network connection for readout, this needs an
extra parameter h.
COMMAND PARAMETERS
this section lists the command parameters available to set
the values of command.
command
- 0
- read current time of DCF 77 receiver. If the
receiver is not synchronized with DCF77 sender, the
user is notified appropriately.
- 1
- read topmost dataset off the ringbuffer, if avail-
able.
- 2
- pop topmost dataset off the ringbuffer and advance
to read next available dataset. The next dataset
can be read by issuing command 1.
- 3
- activate 9 temperature/humidity sensors.
- 4
- activate 16 temperature/humidity sensors.
- 5
- read status of weatherstation
- 6
- set intervall time, this requires an extra parame-
ter -i intervall time
- 12
- read all datasets of the weatherstation interface.
This is a recursive combination of command 1 and 2.
FILES
/etc/wth/wth.conf
wthc configuration file
BUGS
Prototype version. Network code probably unreliable.
wthd
wthd - network service of weatherstation interface
SYNOPSIS
wthd [ -d ] [ -p portnumber]
DESCRIPTION
wthd serves incoming network requests to read data of
weatherstation interface, like temperature, humidity, air
pressure, wind speed, wind direction and rain fall. The
DCF77 receiver can be read as well as current status
information. To communicate with wthd a client program is
needed, otherwise telnet access at full functionality is
provided.
OPTIONS
- -p portnumber
- use portnumber to listen on, default is 3900.
- -d
- do not daemonize, stay in foreground
SEE ALSO
wthc(1), telnet(1)
BUGS
Prototype version. Network code probably unreliable.
Description
pcwsr is Free Software to read the PC
weathersensor
receiver sold by ELV (ELV Part No. 68-390-61).
Different
types of weather sensors like temperature, humidity, air pressure, wind, rain
or brightness transmit measured values wireless (at 433MHz). The receiver is
connected thru the serial port. The communication with the computing equipment
is unidirectional, i.e. the receiver writes the sensor data to the serial port
once they are received from the wireless sensors.
radio transmission serial
sensor <--------------------> weathersensor receiver --------> computer
at 433 MHz comm.
computer
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The communication protocol has been published by ELV (ELV Journal 6/2000). It
has been reproduced here.
The communication software pcwsr opens the serial port, sets the serial
configuration right, then loops to receive data from the serial port.
pcwsr - screenshots
A typical screenshot of pcwsr looks like this:
volker@ikarus pcwsr-0.1.2 > ./pcwsr /dev/ttyS0
pcwsr 0.1 - experimental test version
Wed Nov 21 2001 19:54:49 | wind (version 11 at address 0x07) | Speed[km/s] 1.5 | Direct
Wed Nov 21 2001 20:00:37 | indoor (version 11 at address 0x07) | T[°C] 18.1 | H[% rel.hum
|
using the raw option the byte strings are dumped as received:
volker@ikarus pcwsr-0.1.2 > ./pcwsr -r /dev/ttyS0
pcwsr 0.1 - experimental test version
option: raw
Wed Nov 21 2001 20:13:32 : 8 bytes read |2|a7|8c|b4|80|80|80|3|
Wed Nov 21 2001 20:14:04 : 8 bytes read |2|c7|81|b5|ac|87|ce|3|
Wed Nov 21 2001 20:16:22 : 8 bytes read |2|a7|8c|b4|80|80|80|3|
Wed Nov 21 2001 20:16:46 : 8 bytes read |2|c7|81|b5|ac|87|ce|3|
|
Serial communication
A crucial point in the development of the code was to get the serial
communication parameters right. In the first place,
serial line
snooping has been used to test the PC software which is distributed
with the weathersensor receiver. The following settings for the
serial port have been found useful:
speed 19200 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = ;
eol2 = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
lnext = ^V; flush = ^O; min = 1; time = 5;
parenb parodd cs8 hupcl cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
-iuclc -ixany -imaxbel
-opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0
ff0
-isig -icanon iexten -echo -echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke
|
The serial has to be configured to 19200 Baud, 2 stop bits and odd parity.
Also it has to be set to raw mode for input and output by turning off ICANON,
ISIG, ECHO, ECHOE and OPOST.
The data can most simply be received by
Each read will return 8 characters in case everything has been configured
right.
Types of sensors
The following sensors have been tested so far successfully:
| S2000A |
outdoor temperature and humidity sensor |
| S2000W |
wind sensor for speed and direction detection |
| S2000R |
rain sensor |
| S2000I |
indoor sensor for temperature and humidity |
| S2000ID |
indoor sensor for temperature, humidity and air pressure |
Unknown stuff
If the serialline is snooped
using the WS-EMpfaenger.exe binary
which is distributed with the receiver it is noted that the software sends
two byte strings
to the PC weathersensor receiver. The two strings are 9 bytes long
01 ff 00 00 00 00 00 80 04
01 ff 00 00 00 00 00 80 04
|
I don't know howto interpret this.
Licensing
The wth and pcwsr software have been written and are copyright Volker Jahns.
It is Free Software and has been been put under the
GNU
General Public LicenseGPL. For further
information look at the GNU website.
Download
The current versions for download are
For further information also proceed to the
wth project homepage which is hosted by
Berlios.
References
Serial programming
This I found interesting what serial programming under UNIX is concerned.
Weather software
As time passes complexity increases. In the course of programming
the wthc software I got to know several other places which are
concerned with programming software for wireless weatherstations
in the UNIX environment.
As time passes complexity increases. In the course of programming
the wthc software I got to know several other places which are
concerned with programming software for wireless weatherstations
in the UNIX environment. huh, this software is cool.
| Title |
Author |
Description |
| wx2000 |
Friedrich Zabel |
wx2000 - Weather Data Logger Extraction Program (ws2000 model) |
| wx200d |
Timothy D.Withman |
wx200d is a weather station data collector and server daemon
for the WX200 / WM918 weather station hardware. |
| gwx |
Timothy D.Whitman |
gwx is a graphical GTK+ client for the wx200d(8) weather station server. |
| wxreport |
Lukas Zimmermann |
Linux data logging and server daemon software for the WMR918(H) and
WMR968 wireless weather station. |
| wxnet |
Rob Pinelli |
wx/net (weather net) is a free open-source networking application for the monitoring of weather conditions.
|
| wmr918 etc |
Joe Jaworski |
network connect of WMR918. |
| wmr918d |
John Stanley |
Software to talk to the WMR-918 on UNIX. |
| kweather |
Juergen Hochwald |
use KDE for your personal weather report. |
| WeatherUpdate |
Scott Hassan |
Phyton version for use w/ Davis Monitorr II, WM-918, WMR-968. |
| Oww |
Simon J.Melhuish |
One-wire weather - Oww: RISC OS or Linux interface to the Dallas Semiconductor 1-wire weather station. |
| Perl the Ultimeter 2000 |
Jonathan Bradshaw |
PERL scripts for the Ultimeter 2000. |
| Weather Tools |
Alan Jackson |
Weather Tools: PERL scripts for the wmr918. Look how wonderful the windrose plots are. |
| ws2000 |
Wolfgang Bolien |
Software to read the ws2000 weatherstation. |
Meteorology links
These websites contain information on meterological issues.
Further Information
Comments and questions to
Volker.Jahns@thalreit.de, please.
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