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For RS485 operation: Install the jumper shunt onto J3. At small transmission distances speeds up to 35Mbps can be realized with RS485 although the transmission speed will decrease with distance. We start with including the standard library for driving the LCD and declare the D8 pin of the Arduino Nano as an output pin which we will later use to declare the MAX485 Module as a transmitter or Receiver. We will send some data from the transmitter side over the cable from the Nano which is converted to RS485 signals via MAX RS485 Module working in Master Mode. By default, the RS485 connections are not brought out to the Docking Panel’s DB-9 Serial1 Connector, although custom placement of zero-ohm surface-mount resistors on the Docking Panel can route the RS485 signals to the DB-9. A jumper labeled "1 485En" (J4) enables RS485 operation on the Serial1 port if the jumper cap is installed, and configures Serial1 for RS232 operation if the jumper cap is not installed. Serial1 port the default startup serial link. InitRS485() configures Port D to ensure that bit 5 is an output. The receiver input has a fail-safe feature that guarantees logic high output if the input is open circuit.

We will pull the enable pin high to put the MAX485 module in transmitter mode. Do note that both transmitter and receiver circuits look identical the only thing that differs is the code written into it. There are many different types of serial communication protocols like I2C and SPI which can be easily implemented with Arduino and today we are going to look at another most commonly used protocol called RS485 which is very commonly used in high noise industrial environments to transfer the data over a long distance. Noise in the range of ±200 mV is essentially blocked due to common-mode noise cancellation. Sig- lines are twisted as twisting nullify the effect of electromagnetic noise induced in a cable and provide a much better immunity against the noise which allows the RS485 to transmit the data up to 1200m of range. At 1200m of transmission speed, you can use only 100kbps of transmission speed. There are different sets of standard baud rates in use depending on the application. Finally, for master devices, the SPR1 and SPR0 bits determine the baud rate at which data is exchanged.

For the transfer of data, the baud rates of both Master and Slave must be between 10% of each other. Signal High and Lows are measured against the GND level so shifting the GND level will have a disastrous effect on the data transfer. So, in the Arduino code, we will focus on sending the data and display that sent or received data on the LCD screen. 2 Alphanumeric LCD to display the results. 2 Alphanumeric LCD connected to it. In fact, the program works the same as it did before, but now it is using the secondary serial port instead of the primary port - and you didn’t even have to recompile the code! The main reason behind using these Ethernet Cables over normal wires is that they provide much better protection against noise creeping in and distortion of the signal over high distances. We have been using Microcontroller Development Boards like Arduino, Raspberry Pi, NodeMCU, ESP8266, MSP430, etc. for a long time now in our small projects where most of the times distance between the sensors and board is not more than few centimeters at max and at these distances, the communication between the different sensor modules, relays, actuators, and controllers can be easily done over simple jumper wires without us being worried about the signal distortion in the medium and the Electrical noises creeping into it.

Most of the low-cost sensors and other modules like GPS, Bluetooth, RFID, ESP8266, etc. which are commonly used with Arduino, Raspberry Pi in the market uses UART TTL based communication because it only requires 2 wires TX(Transmitter) and RX (Receiver). The circuit diagram given above explains how the onboard MAX485 IC is connected to various components and provide 0.1-inch standard spacing headers to be used with breadboard if you like. It is not a standard Communication protocol, but it is a physical circuit with which you can transmit and receive serial data with other peripherals. In the most common multi-drop RS-485 protocol, one computer is designated as a "master" and the rest of the computers or devices on the serial bus are designated as "slaves". UART is an Asynchronous transmission device hence there is no clock signal to sync the data between the two devices instead it uses start and stop bits at the start and end of each data packet respectively to mark the extremities of the data being transferred. On the other hand, RS485 is more industry-based communication which is developed for a network of multiple devices that can be used over long distances and at greater speeds too.

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