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So, in the Arduino code, we will focus on sending the data and display that sent or received data on the LCD screen. Because differential signals have inherently better signal-to-noise properties, reliable RS422 communications can be sent over much longer distances compared to RS232. 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. This signal synchronizes the exchange of bytes between the QScreen and its peripherals. RS485 is another protocol supported by the primary serial port on the QScreen Controller. There are several protocols that govern the format of exchanged data, with the RS232 protocol used primarily by personal computers, and the RS485 protocol used in industrial control systems. RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off. A true multi-point network consists of multiple drivers and receivers connected on a single bus, where any node can transmit or receive data.

RS423 is another single ended specification with enhanced operation over RS232; however, it has not been widely used in the industry. Many terminals and PCs, however, do rely on hardware handshaking to determine when the other party (in this case the PDQ Board) is ready to accept data. These factors are discussed in more detail in The UART Wildcard: Modem Handshaking Signals. RS422 devices. These networks are often used in a half-duplex mode, where a single master in a system sends a command to one of several "slave" devices on a network. In these distributed processing networks, a variety of machines and instruments work locally, but communicate and share data or resources with one another globally using a single serial link. Single master systems (many other communications schemes are available) offer a straight forward and simple means of avoiding "data collisions" in a typical 2-wire, half-duplex, multi-drop system. Thus, the master has only one input, MISO, which is the slave’s only output.

The master initiates a communications request to a "slave node" by addressing that unit. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol. It does not specify or recommend any data protocol. Although the RS232 protocol specifies functions for as many as 25 pins, each communications channel requires only three for simple serial interfaces: TxD1 (transmit data), RxD1 (receive data), and DGND (digital ground). Independent channels are established for two-way (full-duplex) communications. To solve the "data collision" problem often present in multi-drop networks hardware units (converters, repeaters, micro-processor controls) can be constructed to remain in a receive mode until they are ready to transmit data. Standards have been developed to insure compatibility between units provided by different manufacturers, and to allow for reasonable success in transferring data over specified distances and/or data rates. The connection between two or more elements (drivers and receivers) should be considered a transmission line if the rise and/or fall time is less than half the time for the signal to travel from the transmitter to the receiver.

Likewise, the terminal’s transmit signal /TxD is connected to the PDQ Board’s receive signal /RxD1. The "idle" state (MARK) has the signal level negative with respect to common, and the "active" state (SPACE) has the signal level positive with respect to common. Differential signals can help nullify the effects of ground shifts and induced noise signals that can appear as common mode voltages on a network. Electronic data communications between elements will generally fall into two broad categories: single-ended and differential. RS422 (differential) was designed for greater distances and higher Baud rates than RS232. 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. Here again, 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.

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