Rs232 to rs 485 converter named hxsp-485d

[majde]

hi
i have to connect a plc extendable but without an extension port to amtega 128a controller so
i trie to connect the signals out of th plc i/o extend with this converter and then tried to connect it with a desktop but it seems not working at all anyone has an idea why?

 

[KlausST]

Hi,

The ATMega has TTL/ CMOS level outputs.

You did't say, but I assume the PLC has RS485.
(RS232 is not ued at all, therefore it is unclear why you talk about RS232)

RS485 is half duplex, where you only have one signal (pair) for receive and transmit combined
RS232 is full duplex with one signal for receive and one signal for transmit.

With RS485 you therefore need a signal to select between receive and transmit..

Additionally you need to select the correct baud rate, UART setup (8N1), and you need to implement the PLC protocol in your AVR software.

*****
Your post lacks a lot of informations, therefore it is impossible for us to find out where your problem is.


Klaus

 

[majde]

right but the plc i/o extension is 0-5volts
and the atmega128a tx and rx pins are 0-5volts so how can i connect between them

 

[KlausST]

Hi,

...now both are 5V, so neither RS485, nor RS232... are you sure both are serial interfaces in UART style?

Please first find out informations of both interfaces. Basic informations.
Data rate, distance between both devices and so on.

Then find out if you need galvanic isolation between both devices.

Klaus

 

[FvM]

RS485 interface voltage would be around 5V, but the OP didn't yet tell why he assumes that his "plc i/o extension" (whatever it is, no brand or type yet told) has a RS485 interface.

As far as I understand, he wants to interface it with a ATmega128 UART port, so the baud rate etc. can be freely chosen. To interface an µC with RS485, you'll use a driver like MAX485 and connect RxD, TxD and an IO-pin to be used as transmit enable.

 

[majde]

PLC EXTENSION PORT PROVIDE 0 5 VOLTS BUT LIKE THE RS485 IT WORKS as half duplex and gives two signals a and b i mean
a=!b and the plc transmitts and receive signals in each of the two signals and i want to build a circuit to use this signal in order to send and receive data with the microcontroller
i 'm a not familiar with this things and i need to know how to make this communication for my graduation project.

 

[KlausST]

Hi,

Then read how RS485 works.
There is plenty of information around, because RS485 is a standard:
* google
* wikipedia
* this forum
* almost every RS485 transceiver datasheet
Then you should be able to build the electrical connections to the AVR.

The next will be to find out about the communication setup and tbe used protocol. I assume this is not standard. So nobody and no internet can help you as long as you don't know/say what PLC manufacturer and exact PLC type you use.

Again: first you need to know the basics. Read my post#4.

Klaus

 

[majde]

plc type is tsx 07 31 2824 and i searched in the manufacturer's website and the search returned no results
the manufacturer is
modicon telemechanique and shnider electrical

 

[KlausST]

Hi,

These PLCs incorporate extended communication :
Uni-Telway master/slave link or ASCII link for
transmission/reception.

This extension link can be used exclusively as a Modbus slave link.

Nano PLCs have an RS 485 serial link extension port,
supporting the Modbus protocol (depending on the model).
It is used to perform the following requests :
Up to 28 Nano PLCs can be connected over a distance of
200 m for user-definable speeds of 1.2 to 19.2 K bits/s.

and a lot more.....

... these are just some informations you get when you open the datasheet and do a search on "extension"

It makes no sense, that we read the datasheet and post you the informations.

--> please read the datasheet by yourself.

Klaus