I'm coding a program for PC, which needs to talk to the 8052 devices on RS485 bus. I have a RS485 converter which supports full duplex and half duplex (controlled by RTS line as described at http://www.8052.com/forum/read.phtml?id=4267 ) options.

I have to use the half duplex option, and I believe that I've managed to control the RTS line ( http://www.8052.com/forum/rea...&top=70080 ). However, I could not manage to get answer from the 485 devices properly.

The boards on the RS485 bus supports both RS232 and RS485 communication (using the same communication code), and I've verified by the RS232 interface that they send correct responses to the requests of the PC. However, when I switch to RS485, I cannot get proper responses. Since the communication sw on the devices are same for both 232 and 485, I believe that there is something wrong with the converter or the PC configuration.

I basically get messages with the first byte lost or completely trash answer. Please note that I tried both letting the OS to toggle the RTS line and toggling it by my code. ( http://www.8052.com/forum/rea...&top=70080 )

Does the converter need some time for switching between transmit and send modes? Or is there anything I should check?

PC sends bytes and just toggles to receive mode. Devices send multi byte answers after receiving whole message.

Another thing to consider would be RS485 part of the 8052 devices. You may think that they fail to send answers on the bus. However, I know that they are OK since when I switch to full duplex mode on the converter (even the Tx and Rx lines are looped) I get bytes the PC sent (Tx and Rx looped) followed by the expected response from the 8052 devices.

Any ideas?