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5V power supply and the rated current is 300 μA. It works on half-duplex communication to implement the function of converting the TTL level into RS-485 level which means it can either transmit or receive at any time, not both, it can achieve a maximum transmission rate of 2.5Mbps. MAX485 transceiver draws a supply current of between 120μA and 500μA under the unloaded or fully loaded conditions when the driver is disabled. We will pull the enable pin high to put the MAX485 module in transmitter mode. The receiver input has a fail-safe feature that guarantees logic high output if the input is open circuit. 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. For this reason, frame-level cyclic redundancy checks are much more widely used for validating data from serial links, network connections and storage media. 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.

On the other hand, rs485 cable 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. Twisted pair also allows the transmission speeds to be much higher than what is possible with straight cables. There are many categories of Ethernet cables we can use like CAT-4, CAT-5, CAT-5E, CAT-6, CAT-6A, etc. In our tutorial, we are going to use CAT-6E cable which has 4 twisted pairs of 24AWG wires and can support up to 600MHz. It is terminated at both ends by an RJ45 connector. By connecting pairs of these handshaking signals together, the terminal or PC can be made to think that the PDQ Board is always ready to send and receive data. RS-485 is used in basically connecting the temp sensor or thermostat in the room to the master controller. When we think of long-distance data transfer, we instantly think about connecting to the internet via Ethernet cables. In practice, Cat 5 cables have been used successfully in many installations, but there are some concerns. They are often terminated with 8 pin RJ45 connectors at either end. 2 Alphanumeric LCD, and MAX485 UART to RS485 converter IC connected to each end of an Ethernet Cat-6E cable via an RJ45 connector.

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. Each packet contains 1 start bit, 5 to 9 data bits (depending on the UART), an optional parity bit, and 1 or 2 stop bits. UART transmitted data is organized into packets. 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. Signal High and Lows are measured against the GND level so shifting the GND level will have a disastrous effect on the data transfer. 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. The driver is limited for short-circuit current and the driver outputs can be placed at a high impedance state through the thermal shutdown circuit.

The connection diagram for the above circuit is also given below. A mode fault occurs when the SPI senses that a multimaster conflict (MC68HC11F1 Technical Data Manual, p.8-7) exists on the network as explained above in connection with the /SS input. Daisychaining the network is prefered above a star topology, although both are allowed. All communication cabling to be installed in a daisy chain configuration, no T’s are permitted. Just like it’s older brother RS232, RS485 is a form of serial communication. In this tutorial, we are going to learn about the RS485 communication protocol and how to implement it with the two Arduino Nano we have with us and how to use the MAX485 RS485 to UART conversion Module. Nowadays, we mostly use Wi-Fi for internet connectivity but earlier we used to use Ethernet cables going to each personal computer to connect it to the internet. Category 5 (Cat 5, Cat 5e, and Cat 6) cables are the most common Ethernet cables in use today. It also has onboard LEDs to display the current state of the chip i.e. whether the chip is powered or its transmitting or receiving data making it easier to debug and use. We can also use this to upload to our long-term storage data logger online.