Hi everyone,
I am using Labview to control two devices which must be controlled via rs232 protocol. Communication is so simple; connecting only Tx, Rx, and, ground pins is enough and sending string commands such as 'setvalue' and 'readvalue' makes controlling the device easily possible. My problem is, devices are upstairs and I want to use only one cable to connect both of them(BTW there is only one serial port on my pc). A single cable out of the com port is seperated into two with a 'Y' adapter near the devices. This is where the problem occurs. I can't get response from devices when I connect both of them. However, if I remove the cable between one of the devices and the 'Y' adapter, other works perfectly.
I set up a testing environment at home with three computers such that at a given time, one was 'server' and other two were 'client's. I applied same wiring schema via com ports and the results were strange: both of the clients were able to get messages from server but server was only getting messages from one of the clients. I tried all possible combinations like exchaning server with client1 and client2. No luck... Same happened. Server computer was able to read messages sent by only one of the clients. Strange enough, in case of connecting my devices upstairs, I could not get response from any of them.
I am not able to locate the source of the problem unfortunately. As far as I can imagine, it might be diffrence in the ground pins voltage levels of the three of the computers and/or devices. Can someone please explain me what's wrong with my wiring setup? And, if it is completely out of the abilities of the rs232 protocol, what are the other cheap solutions? FYI, my devices can also use rs485 protocol to communicate.
Thanks in advance.