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". The device that initiates a data transfer is the master, and all other devices on the network are slaves. This method is one of the simple and easy to implement methods to transfer the data over long distances. Data rates of up to 10M bps are supported over short distances (40ft.). At the four-thousand foot distance limit, data rates of up to 100K bps are allowable. If your application requires use of the secondary serial port as well as other interrupt routines, the key is to keep the interrupt service routines short and fast. A serial communications cable is also supplied with QScreen Starter Kits. The value of each termination resistor should be equal to the cable impedance (typically, 120 ohms for twisted pairs).

Twisted pair wire with a characteristic impedance of 120 ohms is recommended with 120 ohm termination at each end of the communications line. In general RS485 is designed for multi-drop, "daisy-chain" operation over a single twisted pair cable with a nominal characteristic impedance of 120 Ohms. The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs). The receiver load impedence is 12K ohms (or higher) and transmitter "leakage" current is ±100µA (or less) in either the powered or unpowered state. They have Shielding Jacket over the insulation layer to protect against the Electromagnetic Interference and also each pair of wires is twisted together to prevent any current loop formation and thus much better protection against the noise. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive.

RS485 is used in many computer and automation systems. 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. 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. When we think of long-distance data transfer, we instantly think about connecting to the internet via Ethernet cables. Do play around with transfer speed on your own and give a try to other ethernet cable types too. 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.

If you are running Serial2 at 4800 baud, the rest of your application must be able to function properly using the remaining portion of the CPU time. BMS MUST BE TURNED OFF TO UPGRADE THE MODULES. • Video Output:1 channel CVBS output, 1 channel VGA output,(1 channel aviation plug). The complete working of this project can be found in the video linked below. As it is a half-duplex IC hence it can not both transmit and receive at the same time. Because matters of protocol are left to the user, what is rs485 cable it is often difficult (if not impossible) to connect RS485 devices from different manufacturers on the same network. A typical RS485 network can operate properly in the presence of reasonable ground differential voltages, withstand driver contentious situations, provide reliable communications in electrically noisy environments (good common mode rejection using twisted pair cable, shielding provides additional protection), and support thirty-two or more (many IC manufacturers have 1/2, 1/4, 1/8 unit load devices) drivers and receivers on the line. The InitSPI() function provides a convenient way to initialize the SPI as the master at a 2MHz baud rate. Consult the data sheets for any peripheral devices that you are interfacing to the SPI and, if a different configuration is needed, follow the instructions below to set up the appropriate SPI data transfer protocol.