There is a bug in Win9X systems preventing talking to RS232 to RS485 converters. Maybe this is a well-known bug, but I found it in hard way and just want to let you know hoping others not to face such problems. I checked the forum but did not find such info.

I was trying to connect the PC to a RS485 bus with 8052 devices on them. The 8052 devices can only talk half duplex and I have a RS232 to RS485 converter for the PC which supports both half duplex and full duplex communication. For the half duplex mode, I need to loop the Tx and Rx wires on the converter and control the communication (read/write mode) using the RTS pin on the PC.

Checked the RS232 configuration options on PC, and decided that RTS-toggle option is the choice I want. I have tried this option but failed. When checked the RTS line, it is clearly seen that RTS line does not toggle properly. After a little search, I found the following article basically saying that RTS-toggle fails to work for Win9X systems: http://support.microsoft.com/default.a...US;Q140030

I’ve verified that it works successfully for XP.

If you have to support Win9x systems with such configuration, you can toggle the RTS line by code which is hooked before sending the data and on the TxEmpty event sent by the OS.