Swtiching or Hub for rs232 db9

[richarddlh]

I need to connect two computers to a serial device.  When I tied all the 2, 3 ,5's together, the new machine added would work, but the other machine now would not.  Disconnect the new machine and the other machine works again.  Is there an auto switch or hub for DB9 serial ports in order to connect multiple things together?  What is the cheap down and dirty way to get it to work.  I am assuming the extra wiring is dragging the signal down or something.  Any assistance would be great.... 

[Jan Axelson]

With three nodes, you have a network and will need a protocol or set of rules to determine who gets to transmit when.

On the hardware side, you can convert to RS-485.

See:

http://www.lvr.com/serport.htm

[ruutboy]

Another option would be to put a second serial port in your "main" computer (your choice) and pass-thru the data from the serial device through the main PC to your second PC. It keeps the coding very simple, and if your data device isn't "network aware", then networking would be difficult to say the least. That, and the cost of one additional serial device (be it USB or a additional card) is going to be cheaper than going RS485 for everything. This assumes that your devices are within 50' of each other. Otherwise, "Serial Port Complete" has some tricks that you can use to get extra distance.

What is your "data" device? Does it understand Modbus?

And depending on your device, if it's located in the center of your network, and the distance between PC1 and PC2 is greater than 50', then consider installing a serial splitter such as a http://www.bb-elec.com/Products/Serial-Connectivity/Serial-Data-Tools-Adapters/Port-Splitters.aspx

[Jan Axelson]

Yes, good suggestion, just use a USB/serial converter.