Help with an RS-232 to Ethernet converter!

[JettaKnight]

There's this nugget:

The WRL with a null modem adapter, may be plugged directly into computers equipped with RS-232 interfaces.

So, yes, it's a DTE.


Can you connect to the bridge with a straight cable? If so, use a straight cable from the weather station to the bridge.

 

[bulletsmith]

I have a question.

You have a device that is meant to be communicated with via rs232. You have a modem that converts to ethernet. Are you trying to connect your computer to the ethernet port on this modem, and use the provided software to communicate with the device (weather station)?

I'd like to suggest that your software has no idea how to communicate to the station via tcp. If it's looking for a db9 port to communicate with I can see why you are not getting a response. If you use a modem on both ends so your equipment sees the rs232 port it expects on each end. The ethernet link in the middle is invisible, the equipment simply thinks it's connected using a standard cable.

 

[looney2ns]

Ok after further head banging on the wall moments and a lot of digging, I find that the USR RS232-24 only use's the tx rx and grnd pins. Nothing else is active on it. Using an ohm meter on the USR to trace pins to the circuit board pretty much confirms this.

I ran across the following article that leads me to believe some subset of what he say's may be used in my case by jumpering pins on the weather stations RS232 port.


Not sure why pic isn't showing, click on it and it will open in another window.

Article:
A Null Modem is used to connect two DTE's together. This is commonly used as a cheap way to network games or to transfer files between computers using Zmodem Protocol, Xmodem Protocol etc. This can also be used with many Microprocessor Development Systems.

Null Modem Connections
Figure 1 : Null Modem Wiring Diagram

Above is my preferred method of wiring a Null Modem. It only requires 3 wires (TD, RD & SG) to be wired straight through thus is more cost effective to use with long cable runs. The theory of operation is reasonably easy. The aim is to make to computer think it is talking to a modem rather than another computer. Any data transmitted from the first computer must be received by the second thus TD is connected to RD. The second computer must have the same set-up thus RD is connected to TD. Signal Ground (SG) must also be connected so both grounds are common to each computer.

The Data Terminal Ready is looped back to Data Set Ready and Carrier Detect on both computers. When the Data Terminal Ready is asserted active, then the Data Set Ready and Carrier Detect immediately become active. At this point the computer thinks the Virtual Modem to which it is connected is ready and has detected the carrier of the other modem.

All left to worry about now is the Request to Send and Clear To Send. As both computers communicate together at the same speed, flow control is not needed thus these two lines are also linked together on each computer. When the computer wishes to send data, it asserts the Request to Send high and as it's hooked together with the Clear to Send, It immediately gets a reply that it is ok to send and does so.

Notice that the ring indicator is not connected to anything of each end. This line is only used to tell the computer that there is a ringing signal on the phone line. As we don't have a modem connected to the phone line this is left disconnected.

Thoughts?

 

[looney2ns]

I have a question.

You have a device that is meant to be communicated with via rs232. You have a modem that converts to ethernet. Are you trying to connect your computer to the ethernet port on this modem, and use the provided software to communicate with the device (weather station)?

I'd like to suggest that your software has no idea how to communicate to the station via tcp. If it's looking for a db9 port to communicate with I can see why you are not getting a response. If you use a modem on both ends so your equipment sees the rs232 port it expects on each end. The ethernet link in the middle is invisible, the equipment simply thinks it's connected using a standard cable.

I am working with the developer of the software that I use to enable TCP comms. He has it working for other weather stations, just trying to get mine ironed out.
And so far, I've been using Putty to manual communicate with the weather station, which use's tcp.

 

[Cameramonkey]

Bullet, the ethernet device uses software locally to emulate a serial port and sends the signals via TCP packets to the device, where it converts the bits back to analog. The extender is designed to extend a physical serial port and present it as if you were sitting right there.

I think it sounds like you need a null modem cable.

 

[bulletsmith]

Bullet, the ethernet device uses software locally to emulate a serial port and sends the signals via TCP packets to the device, where it converts the bits back to analog. The extender is designed to extend a physical serial port and present it as if you were sitting right there.

I think it sounds like you need a null modem cable.

I see, so the device comes with it's own emulate software? I missed that.

 

[looney2ns]

To recap: based on my post #23 above.

Using just pins 2, 3 and 5 on the Weather Stations Serial port DB9 does not work, straight or null doesn't matter.
Pins 1 & 9 on the weather stations DB9 are not used in any way by the station.

The RS232 to ethernet converter I bought ONLY use's pins 2,3,5 on its DB9. Other pins are not used.

The weather station is expecting handshaking and it's not getting any.

So on the weather station DB9, can I tie pins 4 & 6 together and Pins 7 & 8 and possibly make this work?

And not fry anything in the process?

 

[Hop]

You might want a rs232 tester. I've used one like this to debug my car ECU programming and logging.
https://www.amazon.com/CableMax®-RS...8&qid=1471750285&sr=1-1&keywords=rs232+tester

Digi does make some single port converters. You might find some of their data sheets helpful.
Compact Serial Server - Digi International

 

[looney2ns]

Update: Problem solved.

Finally got a hold at someone at TWI that understood what I was trying to accomplish. Tying pins 4 & 6 together at the station on the RS232 DB9 was the solution. So now my $20 TCP server is replacing 85' of serial cable!

Thanks for all the suggestions.

 

[JettaKnight]

Huh. So they actually use hardware flow control... morons.

 

[T.Lex]

I gotta say, this has been a fascinating thread! I wish I'd had something to contribute.

 

[looney2ns]

Huh. So they actually use hardware flow control... morons.

These stations have been around since before Gore invented the internet. They were originally used with a standalone modem for dial up remote access. They just haven't changed much over the years.