For those of you interested in the details, here’s how it works: The low-level serial driver routines named Key(), AskKey() and Emit() are revectorable routines that can be redirected to use either of the serial ports. Two asynchronous communications ports named Serial1 and Serial2 can each be configured for RS232 or RS485 protocols. These protocols are summarized on this page, but for more information regarding their data formats and their use for simplex or multi-drop serial lines, consult Understanding Serial Communications (but keep in mind that that page is directed to the use of the UART Wildcard, so it uses different driver functions). 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. 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.

Do play around with transfer speed on your own and give a try to other ethernet cable types too. They translate the bit-by-bit data on the serial cable into bytes of data that can be interpreted by the operating system or by your application program. If your application requires communicating with a device that expects to receive a parity bit, the generation of a parity bit and selection of even or odd parity, and whether there are seven or eight data bits in each byte, is performed by setting or clearing bits in the configuration registers SCI0CR1 for Serial1 and SCI1CR1 for Serial2. For example, at 4800 baud (bits per second), each bit lasts about 200 microseconds (µs), and if communications are full duplex (e.g., if the QScreen Controller echoes each incoming character), then there is a serial interrupt every 100 µs or so. Now in the loop, we write a continuously increasing integer value on the Serial lines which is then transmitted to the other nano. This value is also printed on the LCD for display and debugging. Since both channels can operate simultaneously and independently, serial debugging can be performed while the application program is communicating via its primary channel.

Independent channels are established for two-way (full-duplex) communications. If two bits are received incorrectly, the error will go unnoticed by parity checking. An optional parity bit can be specified to enable error detection by the UART. If PT is set, all transmitted bytes with a parity bit will have an odd number of total '1' bits. The above parity settings will also determine how incoming data is interpreted (whether the most significant bit is considered a parity bit or part of the data being transmitted, and how many bits total to expect in each byte). Now coming to the setup part. Although the maximum standard baud rate of the primary serial port is 19200 baud, nonstandard baud rates of over 80 Kbaud can be attained by the 68HC11's on-chip UART and the onboard RS232 driver. The Serial ports are implemented by the dual on-chip hardware UARTs (Universal Asynchronous Receiver/Transmitters) on the Freescale 9S12 (HCS12) microcontroller. The advantage of using Serial1 for RS485 is that the Serial1 RS485 signals are also available on the Docking Panel, while the Serial2 RS485 signals are available only on the PDQ Board’s Serial Communications Header.

EIA-485 (formerly RS-485 or RS485) is an OSI Model physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. EIA-485 only specifies electrical characteristics of the driver and the receiver. 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). RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol. RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. The standard specifies a differential form of signalling. Electronic data communications between elements will generally fall into two broad categories: single-ended and differential. 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.

If you cherished this article and also you would like to be given more info about rs485 cable nicely visit the web-site.