See rs485 example of two arduinos communicating over re 485 here.
Arduino rs485 beispiel. This shield the perfect choice for such kind of applications. Next we will proceed to explain how this example works. Rs485 library for arduino enables sending and receiving data using the rs485 standard with rs485 shields like the mkr 485 shield.
Connect the other end of the power wire red wire from the arduino mega to the vcc power pin of the rs485 module picture 1 place a jumper between the de and re pins of the rs485 module picture 2 connect the other end of the tx wire green wire from the arduino mega to the di driver input pin of the rs485 module picture 3. Its possible to use an arduino as slave and with some restrictions also as master in modbus applications but a rs485 interface is needed. Rs485 is a physical connection standard for serial data transfer.
Simplecomm libraries installed on your arduino ide. Check out the detailed tutorial on rs 485 modbus serial communication with arduino as master. The network has 120 ohm termination resistors at each end.
Connect correctly the communication ports of rs 485 between both plcs. More details about rs 485 modules here. See the example rs485 network diagram scroll down.
Rs 485 example communication and how to use our libraries. Our rs422 rs485 serial shield is a fully galvanic isolated serial communication hat designed for use with the arduino uno and other compatible boards like arduino 101 stm nucleo. There is also a usb to rs485 module top right for use on pc s.
The example here shows two arduinos connected with low cost rs485 electronic bricks or breakout boards that use a max485 chip. In half duplex mode it has a data transfer rate of 2. See on rs 485 communication.
This library supports the maxim integrated max3157 and equivalent chipsets.