What's similar / not smiliar between rs-485 and rs-232

[Armando1223]

Hi everyone,

I'm a student and working on a project. I am supposed to communicate with a device. There is behind this device, a RS-232 port. The problem, is that the device only indicate me the baud rates with noticed "RS-485 interface" (there is not noticed parity, number of stop-bit ...). 

I tried to communicate with him with RS-232 port but it didn't work ... 😞 . I would like to know if there is a difference between RS-232 and RS-485 port because i found nothing on internet ...

Thanks you very much ! 

PS : i'm a french student, sorry if my english isn't very good ! ^^

[crossrulz]

The voltage levels are completely different.  On top of that RS-485 and RS-422 use differential pairs instead of single wires.  Otherwise, there are not much difference when at short distances.  RS-485 and RS-422 can travel a lot further.  Here are some links:

RS-232 

RS-485 

[Armando1223]

Thanks for you answer. Are the ports for 232 and 485 the same ? (the one with 9 pins). 

[crossrulz]

The connectors for both are commonly DB-9.  But the pin-outs are completely different.

[Armando1223]

Ok i get it. I still have two question : are the cable working with both port ? Or are there cables for 232 and cables for 485 ? 

And on a RS-485 connexion, should we only get the baud rate (no partity , no stop bit ... ?) ?

[crossrulz]

Depends on the cable.  There are "NULL Modem" cables that swap the RX and TX lines.  And then there are straight through cables.  The straight through cables should work for both.

For standard UART, you should have more parameters than just the baud rate.  The best you can do is assume the normal defaults as per the VISA Configure Serial Port.