How to connect a weather station WS2355 (or WS2300) to Weather Underground with Arduino

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There are several softwares that enable the publication of the weather data of a professional weather station, but they all work on PC, so we should connect the weather station to a computer and leave it on, the idea is not good because the computer takes up space and consumes a lot. At a time when we should spare the energy, its not a good thing.
The project we’re talking about instead operates as a stand-alone application and allows you to publish the weather station data independently on http://www.wunderground.com, “forgetting” the PC consumption and even the desk space.

Arduino controls the dialogue with the weather station to acquire the data and also the Ethernet interface to transfer them, by making the necessary connection to the Internet via ADSL, passing by a router pointing to the IP address of the Weather Underground site and transferring information using the TCP / IP.

Our project

This circuit reads data from a weather station with serial interface and upload the data collected on http://www.wunderground.com.
Not all stations are equal, therefore, our circuit can not be universal but it is indicated specifically for stations La Crosse WS2355, WS2300 or WS2350.

The choice of weather station WS23xx was dictated primarily by a consideration: it has a convenient serial interface to connect and dialogue with a microcontroller such as Arduino.
We chose www.wunderground.com site because it allows anyone to upload their weather data, but also to monitor the temperature, humidity, pressure, wind etc. on line. Also on this site there are many widgets that allow you to integrate data in website or blog.
An example is the Widget for the home page of Google.
The data sent by users are publicly available, then from the home page we can specify the geographic area that interests us and we will see a screen that lists all of the corresponding stations.

How does it work?

The system has two circuit: one is the famous Arduino UNO and the other is a shield that integrates the Ethernet module WIZnet (you may, of course, use the the original Ethernet Shield), as well as a TTL/RS232 logic level converter MAX238 type. The converter allows you to adapt the serial levels of weather station to the TTL levels of Arduino.
Please be aware that the communication port of the weather station is not a simple RS232, because it has no ground reference. The DTR line must have a negative voltage while the RTS must be positive. The lack of common ground leads to the hypothesis (remember that there is no official document) that these two lines are taken as a reference of logic levels used in communication. It is a system that not only allows the use of serial connections relatively long, but also gives the opportunity to agree devices with different voltage levels on the serial port.
To communicate with La Crosse, the speed of the serial device (in our case, the Arduino module) must be set to 2,400 bps, with blocks of 8 bits, no parity and one stop bit (2400-8-N-1).
The memory map of the weather station, like many other unofficial information on the WS2355 is on the site http://www.lavrsen.dk/foswiki/bin/view/Open2300/WebHome.

The hardware

The jumpers on the lines T3IN and R3OUT (respectively RS232/TTL converter output and RS232/TTL converter input) let you choose which lines use for Arduino communication: we give you the opportunity to choose if use the serial hardware TXD and RXD or the two I/O digital D2 and D3 emulating a serial port with the appropriate library that can be downloaded from the website http://arduiniana.org/libraries/newsoftserial.

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The sketch