How can i test RS-485

i see that useful thanks, what i want to do is to test if the ic is wotking or not, I am a maintenence engineer and for devices that have communication fault we cant be so sure if that ic (MAX458) for example is faulty , an so i am looking for a way to test the ic itself.

Ow. In that case I'd build a little testbed. The cheapest would most likely be 2 arduinos, one arduino CAN shield, and one custom little test-jig that you create to put the IC-under-test on. Test firmware already exists

So I think you can go for a simple circuit to test the chips on their receive and transmit functions.

See datasheet

Perhaps Jan Axelson's book 'Serial Port Complete' might help you ?

http://janaxelson.com/spc.htm 

It covers the basics of serial communications, covers working with RS485 networks, and includes some programming.

Another useful reference might be this e-Book 'A Practical Guide to Using RS-422 and RS-485 Serial Interfaces'

https://advantech-bb.com/wp-content/uploads/2014/12/RS-422-RS-485-eBook.pdf

Thanks a lot!.

Yeah no problem, here it is:https://www.analog.com/media/jp/technical-documentation/data-sheets/1111.pdf

If you have any questions please feel free to ask - I use these chips in loads of things.

Also here's a diagram showing how to wire it up.
The double-s symbol means "long bit of wire"

and the A wire and B Wire should be a twisted pair.

Oh.. and there's one more thing...
You only need to connect 1 GPIO pin to DE and !RE - because DE is active-high and RE is active low, it means you can connect them both to the same pin. When you drive the pin HIGH you have a trasnmitter, when you drive the pin LOW you have a receiver ;-)

Thanks for that, i keep studying about that topic every day for some hours and now i know the concept but still idk how to add the ic  itself , i want to start only with two ics to test them.

What am trying to say is how to communicate between an pc and pc using the ic , what is the connections and the wiring , what is the code or the procedures, all that i still dont know about , but the concept of RS-485 know i understand what it does,

The main point now is how to insert data to DI what do i need for that?

And also how to receive data from RO like how can i show the data coming out of this pin, what do i need to show these data? so i can compare it with the data i sent on DI (which idk yet how to do that) to ensure if the ic is working well or not.

Ah yeah - ok, so connecting a chip like this to a PC is not as easy as yuo might think.
That's because a PC does not have any GPIO pins, like an Arduino does, or a Raspberry PI.

So what you'd need is another chip first - which has USB and can be programmed to be a "CDC" device.
Such a chip might be the FT232R from FTDI
That will give you TX, RX pins, and a number of other programmable pins such as CTR, DTR, RTS, CTS - you are then able to use one of these as the DE/RE control. Then you can use any kind of serial terminal on a PC to send and receive via RS485.

The datasheet for THAT chip is at https://ftdichip.com/wp-content/uploads/2020/08/DS_FT232R.pdf and it includes (section 7.2) a schematic on how to make a PC to RS485 convertor! The chip which they call "SP481" in the example, could be replaced with a MAX485 as it has the same pinout.

Ok that will help a lot thanks, i will study that and will tell you about the news.