Now in the loop, we check if there is anything available on the serial port and then read the data and since the incoming data is an integer, we parse it and display on the connected LCD. Now in the loop, we write a continuously increasing integer value on the Serial lines which is then transmitted to the other nano. EIA standards where previously marked with the prefix "RS" to indicate recommended standard; however, the standards are now generally indicated as "EIA" standards to identify the standards organization. While the standards bring uniformity to data communications, many areas are not specifically covered and remain as "gray areas" for the user to discover (usually during installation) on his own. 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.

In its simplest form, a pair of converters from RS232 to RS422 (and back again) can be used to form an "RS232 extension cord." Data rates of up to 100K bits / second and distances up to 4000 Ft. Since it uses a differential line over twisted pair (like EIA-422), it can span relatively large distances (up to 4000 feet or just over 1200 metres). Electronic data communications between elements will generally fall into two broad categories: single-ended and differential. Each RS232 driver uses inverting logic and implements a single-ended bipolar output voltage (that is, one signal that swings above and below ground). The QScreen Controller’s kernel software contains a complete set of high level driver routines for the Serial2 port, and these functions are summarized in the Control-C Glossary. QED-Forth includes three built-in routines to facilitate control of the RS485 transceiver. The two lowest order bits in the SPCR control register, named SPR1 and SPR0, determine the data exchange frequency expressed in bits per second; this frequency is also known as the baud rate. Transmissions are always initiated by the master device, and consist of an exchange of bytes. The SCK pin clocks the serial A/D’s CLK input which causes the A/D’s conversion result to be transferred to the master via the MISO line.

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. 12 V and -7 volts will allow correct operation of the receiver. RS423 is another single ended specification with enhanced operation over RS232; however, it has not been widely used in the industry. The snap switch located on the TSX08PRGCAB programming cable are used to choose a different mode of operation. We will pull the enable pin high to put the MAX485 module in transmitter mode. The DWOM bit (port D wired-or mode) should always be set to 0. Setting DWOM to 1 takes away the processor’s ability to pull the Port D signals high unless there is a pull-up resistor on each bit of the port. We will pull the enable pin high to put the MAX485 module in receiver mode.

Differential signals can help nullify the effects of ground shifts and induced noise signals that can appear as common mode voltages on a network. The standard specifies a differential form of signalling. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol. EIA-485 only specifies electrical characteristics of the driver and the receiver. These characteristics include: definition of a unit load, voltage ranges, open-circuit voltages, thresholds, and transient tolerance. These characteristics make RS-485 useful in industrial control systems and similar applications. This allows RS-485 to implement linear bus topologies using only two wires. The specification allows for data transmission from one transmitter to one receiver at relatively slow data rates (up to 20K bits/second) and short distances (up to 50Ft. @ the maximum data rate). EIA-485 (formerly RS-485 or RS485) is an OSI Model physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. In theatre and performance venues, RS-485 networks are used to control lighting and other systems using the DMX512 protocol. RS-485 is used for low-speed data communications in commercial aircraft cabins' vehicle bus. Because the software UART is interrupt based, competing interrupts that prevent timely servicing of the Serial2 interrupts can cause communications errors on the secondary serial channel.

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