Part 1 – Put your Lacrosse WS-23xx weather station online

Setting up a Serial Device Server

I got a WS-23xx (I think 17, but it was just called “pro”) for Christmas. The PC softwhere which comes with it is horrendous. In addition, I didn’t want to have to have a PC running all the time in order to upload data to the web. This hack will show how I took a Lantronix MSS-T1 Serial Device Server, and modified it in order to make it work with the 2317. Once the Serial Device Server is working, the 23xx essentially has an IP address and can be accessed from any computer that could normally access that IP.

1. Acquiring a Serial Device Server

What is a Serial Device Server? It is a powered electronic device which converts an RS232 serial data to data that can be transferred over a TCP/IP network (See figure 1. for an example Lantronix MSS1-T). On EBay, I have found that (“serial to ethernet”, “serial device server”) is the best search for a Serial Device Server. I still have an automated daily search using that string. The two categories below are probably the best EBay categories in which to look for a Serial Device Server.

Listed in category: Computers & Networking > Networking > Other Networking Equipment
Listed in category: Computers & Networking > Servers > Other Servers

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figure 1. A Serial Device Server, the Lantronix MSS1-T

2. The MSS1-T Micro Device Server

I was able to purchase the Lantronix MSS1-T onEBay for about $20 shipped. On Lantronix website, this product is listed under discontinued products. I downloaded the manuals ( Install Guide | Ref. Manual) and the Windows software (EZWebCon b2.1/1 ) to control the MSS1-T. I believe I even updated the firmware of the device I purchased (v3.6/4).

I had a lot of trouble first connecting to the server. At first I thought I might have a dud, but eventually, I was able to connect the EZWebCon software to the server and configure it. It is pretty unlikely that that the server you get will have an IP address that is suitable for you. The EZWebCon software provides a way to access the server by it’s MAC address for configuration, so the IP address does not have to be accessable. Use Action->Assign IP Address to connect to your server. Just type in the MAC Address (labeled on the bottom of the device) and you will be able to assign the server an IP address so you can access it from any computer on your network with a telnet client.

The most important settings that need adjustment, outside of the IP address are the port parameters. To edit the settings, double-click on your server on the EZWebCon main page. Then click on Maintanance, click on Ports and press the Select button. My port is set up as shown in figure 2.

ezscreenshot-1.PNG

figure 2. Port setup in EZWebCon

2.1 Hardware Modification to the MSS1-T

To make the MSS1-T work with the ws23xx, a hardware modification is required. The MSS1-T uses an odd serial protocol which is described well on the Open2300 website.

DTR and RTS are not used for handshake. They are steady DTR at negative voltage and RTS at positive voltage.

Since there is no ground it seems that the WS2300 uses the DTR and RTS to define high and low. DTR must be low and RTS must be high for the communication to work. link

By probing the outputs of the MSS1-T, I found that RTS was already driven high by default. However, DTR was not driven to the necessary value for the 2317. I cracked open the case of the MSS1-T and found the RS232 buffer, a LT1133ACSW chip (webpagedatasheet) from Linear Technology. By tracing the DTR pin on the serial port back to the LT1133, I found that it was driven by pin 7, which is driven by an input on the LT1133 on pin 19 (through the RS232 driver which is an inverter). See pinout below.

LT1133ACSW Pinout
figure 3. LT1133ACSW Pinout

In order to drive the DTR signal low as required by the WS2317 for it’s serial protocol, I needed to pull up the DTR input on pin 19. To accomplish this, I carefully lifted the pin (See Figure 4), and soldered a wire, through a pull-up resistor (sacrificed from an old board), to a +5V header (See Figure 5).

Lifted Pin
figure 4. Lifted Pin

Pin Pulled High
figure 5. Pin Pulled High

The final picture I took before I put the case back together is shown in Figure 6.

Whole MSS1-T
figure 6. Whole MSS1-T

Now the MSS1-T outputs the correct level on the DTR signal. The WS23xx can be accessed from any computer which can access the IP address of the Serial Device Server. There are many commercial applications for the PC which can emulate a windows COM device and connect to a Serial Device Server such as the MSS1-T. I had success with a trial version of one such application, tcpcom from TALtech. Using this software I was able to connect to the WS2317 through the emulated COM port with the Lacrosse-provided PC software, HeavyWeather. My ultimate goal is to not be tied to the PC or the Heavyweather software in order to update data from my weather station onto the web. In the next entry, I will discuss my Linux-based solution to these problems.

3. Other (Better?) Device Servers

Lantronix Device Servers seem to be some of the more popular servers on EBay, at least in my price-range. When the MSS1-T comes up it can be had for about $30. The UDS-10 and UDS100 also come up fairly often. However, these servers go for about $40-$60. I have been looking for a reasonably priced UDS-10 or UDS100, because I believe they are capable of driving the DTR and RTS pins through software, thereby avoiding the above hardware modification. They are newer devices and can also use the Lantronix virtual COM port software for Windows.

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