RS232/RS485 converters

  • Thread starter EC-Hector Rodriguez Alvarez
  • Start date

Thread Starter

EC-Hector Rodriguez Alvarez

I got some RS232 to RS485 converters (model 485LDRC of B&B Electronics). This converter doesn't use the handshaking signals (CTS and RTS) from RS232 that appear in my actual case.
Can anyone tell me how to solve this situation?

Best regards,
Hector Rodreguez Alvarez
I don't know B&B,but I have been used some RS232 to RS485 converters before.
To the protocol of your application: if the
message you send or received have a terminal code, then you can decide whether the interchanged message is over by the terminal code;

If there is not any terminal code, then the length of the interchanged message should be certain,so you can decide when to finish sending or receiving a certain message.remember! because no handshaking signal there, so the length of your received message should be ("the length of the message you sended just now"+"the length of the message you should received this time"),at last,just get what you want from the "too big" message you received.

Paul Breneman

That model has "Automatic Send Data" control per their catalog. There are dip switches to set the timeout between 1 and 4 msec. so if you have those set properly you shouldn't need RTS control.

Paul Breneman
Hi Hector,

I found on my experience that usually CTS and RTS can be shortened between them, because the handshaking is now mostly made by software. This is also reflected by the choice B&B (and most others manufacturers of such devices) made to not include them in RS232 side.

best regards/Luigi
Hi Hector,
RS485 converters sometimes have dipswitches that control how it reacts to the RS232 input. Since RS485 is usually a 2 wire (+ gnd) signal, the key point is does the converter pass your data on through to the RS485 side. If the software signal coming in needs to see the CTS RTS signals, you may be looking at a software change. If you have the source code, you could change it yourself. I have had good luck with RS485 converters from Omega (CAT-285) which have the aforementioned dipswitches.
B&B sells at least one RS232-485 converter with 2 channels, one for TX/TX, and one for RTS/CTS. It is an optoisolated unit that mounts on a snap
trak. I think the P/N is 485OPINA and 485PSIN, or something close to that.