But if you are building a control system with these development boards over a distance greater than 10 to 15 meters, then you should take the noise and signal power into consideration because if you want your system to work reliably, then you cannot afford to lose the data while transferring. When we think of long-distance data transfer, we instantly think about connecting to the internet via Ethernet 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. But there are some limitations to it as it cannot support multiple slaves and multiple masters and the maximum data frame is limited to 9 bits. After configuring the SPI system to communicate on a properly connected network of devices, sending and receiving data is as simple as writing and reading a register.

So, in the Arduino code, we will focus on sending the data and display that sent or received data on the LCD screen. 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. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds. Its simplest implementation requires only three wires: one to transmit serial data, a second to receive serial data, and a third to provide a common ground reference. This works well and prevents the existence of ground loops, rs485 cable a common source of communication problems. You need a special Ethernet cable for realizing this communication protocol. 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. 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.

Previously we have also performed MAX485 communication with Arduino and also MAX485 Communication with Raspberry pi, you can also check them out if interested. Serial data is shifted out least-significant-bit first. In this project, we have only used a baud rate of 9600 which is well under the maximum transfer speed we can achieve with the MAX-485 Module but this speed is suitable for most of the sensor modules out there and we don’t really need all the maximum speeds while working with Arduino and other development boards unless you are using the cable as an ethernet connection and require all the bandwidth and transfer speed you can get. Twisted pair also allows the transmission speeds to be much higher than what is possible with straight cables. At small transmission distances speeds up to 35Mbps can be realized with RS485 although the transmission speed will decrease with distance. 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.

The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network. Suggestions are often made to deal with practical problems that might be encountered in a typical network. A simple network of a PLC, VFD, and an HMI allows remote control of motors in an industrial setting. The next section describes the registers that configure and control the QScreen Controller’s SPI. Configured as a master device, the QScreen transmits bytes via the "master out/slave in" pin, MOSI. However, verifying correct parity of bytes received with a parity bit is currently not supported. Even parity means that the bits sum to an even number, and odd parity means that the bits sum to an odd number. Henceforth, we shall consider Slave devices to be measuring instruments with serial communication, even if the cabling is similar for all Modbus devices. The only difference between the master and slave devices is that the master initiates the transmission. The RS485 receiver compares the voltage difference between both lines, instead of the absolute voltage level on a signal line.