hi'
i am doing a project in which i am using 8 arduino each one has different task and one master arduino which will collect all the data from slave aruino and then will send it to computer, i want to do this job through RS-485 communication , could any one plz give any idea or sourse material how to do it? thanks
Sure, get yourself a pile of MAX488, one per board.
Wire them up per this Maxim Application Note.
http://www.maximintegrated.com/app-notes/index.mvp/id/723 Figure 5 is good
Write yourself "protocol" where by the Master says "#1, give me data" and #1 responds, then the Master does the same for the others, as one example.
thanks for the help , i am going to read out that link
It's easy to use RS485 devices with softwareSerial library.
You just have to add another output pin to the pin 2 and 3 of the 485 driver to enable/disable transmission.
So from, considering the 485 drivers wire it in that way
pin 1 : TX
pin2/pin3 linked together. Enable/disable tranmission
pin 4 : RX
pin 5 : 5V
pin 6 : A positive RS485 signal
pin 7 : B negative RS485 signal
pin 8 : ground.
Really easy to use.
It's better to add a the first and last devices an 120ohm resistor between A and B.
Hope it can help you.