I am looking for the best way to wire communicate between two Arduino boards for 200 m .... I was searching about serial communication protocols "USART, SPI, I2C" and all what i found that i can't reach that distance using them.
I am looking for baud rate about 4800 any thing around that will be good.
thanks in advance.
Use standard serial, and on each end use RS422 adapters (for full duplex) or one RS485 adapter (https://www.sparkfun.com/products/10124) (for half duplex), with twisted wire cable.
Good for up to 1000 m at low baud rates.
thanks a lot, it worked fine using RS422 adapters