Saturday, October 10, 2009

Multidrop network for RS232

I got a requirement to communicate one master device and eight slave devices. I intended to use RS485 half-duplex communication for this system but all devices happened to have only RS232 interfaces. RS232 communication is a sort of communication that is to be used for one-to-one system. There is no problem if only the master device transmits and all slaves are receiving. The problem is that transmit lines of the slaves cannot be disabled and so that they cannot connect to the same line. After analyzing the voltage signals, I have got an alternative solution to this problem. By adding a diode to the transmit line of each slave, I can use the system just like RS485 half-duplex communication. See the following figure for the hardware connection.