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How is the ATmega328P connected to the max485 chip?
The RXD pin of the ATmega328P is connected to the RO pin of MAX485 RS485 chip ,So data received from the RS485 line is sent to the receive pin of the Microcontroller. TXD pin of the ATmega328 is connected to the DI pin of MAX485,So whatever data is transmitted by ATmega328p is sent to the MAX485 chip and out to the RS485 twisted pair cable.
How to connect max485 chip to terminal block?
Connect the Pins A and B of MAX485 chip to screw terminals or Terminal Block Connectors. Connect a 120 ohm termination resistor between the pins A and B. The Full Circuit Diagram in PDF can be downloaded from here (under Source Code and Circuit Diagram)
How to build RS485 using max485 chip?
First thing to do is to build the RS485 section using MAX485 chip. MAX485 chip is available in a 8 Pin DIP package which can be easily mounted on a General Purpose PCB or Bread Board (if you plan on reusing the chip)
How to use ATmega328P as a USART port?
ATmega328P USART Port Programming. Programming the PC serial port using C# and Dotnet framework. ATmega328p is interfaced with MAX485 as shown in the previous circuit diagram. A USB to RS485 converter is used to interface the RS485 twisted pair cable to the USB port of the PC.
Is the max485 chip half duplex or duplex?
The MAX485 chip can only transmit or receive at a time ,so communication is half Duplex. The AVR Atmega side code is written in Embedded C using ATMEL Studio 7. The PC side code is written in C# using Microsoft Visual Studio 2019. All the Code files,Circuit diagram,Datasheets are available on our github repo.Use the below links to access them
Why are max485 IC’s Ro low while listening?
If I place a termination resistor (120 ohm), it is obvious that A-B pins are no longer high impedance. According to the datasheet, if A-B pins are not in high impedance, MAX485 ic’s RO (Readout) is low while listening.