Long Distance Wired Serial Communication with Arduino using RS485 and CAT Cables > 자유게시판

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. Thus in Table 9 6 , RTS1 is connected to CTS1, and DSR1 is connected to DTR1 and DCD1 onboard the QScreen Controller using zero ohm shorting resistors. Ideally, the two ends of the cable will have a termination resistor connected across the two wires and two powered resistors to bias the lines apart when the lines are not being driven. We will pull the enable pin high to put the MAX485 module in transmitter mode. 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. 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. While RS422 is comparable to RS485, it is limited to unidirectional data traffic, and is terminated only on the end of the line opposite the transmitter.

While the conversion is "transparent" the software must be able to communicate with the expanded network features. While the standard only supports low data rates and short line length (50ft.) it is still widely used and, very useful in many applications. The maximum RS485 cable length is typically listed as 1200 meters or about 4000 feet. Up to 100 units may be connected to the same RS485 interface. In fact, the program works the same as it did before, but now it is using the secondary serial port instead of the primary port -- and you didn’t even have to recompile the code! The primary channel’s UART translates the bit-by-bit data on the serial cable into bytes of data that can be interpreted by the QED-Forth Kernel or by your application program. Pre-coded device drivers configure the SPI for a standard data format, and routines defined in this chapter make it easy to customize a data format and baud rate for your application. The standard does not discuss cable shielding but makes some recommendations on preferred methods of interconnecting the signal reference common and equipment case grounds.

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. The recommended arrangement of the wires is as a connected series of point-to-point nodes, a line or bus. Ideally, the two ends of the cable will have a termination resistor connected across the two wires. The resistance of the twisted pair cable will drop the voltage difference as it travels down the wire. The GROUND line serves as a common voltage reference for the master and slave. As the master transmits a byte to an active slave (that is, a slave with its /SS input active low), the master receives a byte from the slave. If you are using the QScreen as a slave device and require the /SS signal for your external SPI hardware, configure one of the Port A pins on the Field Header as an input pin.

Thus, the master 68HC11 has only one input, MISO, which is the slave QVGA Controller’s only output. Regardless of the network, however, there are only four signals used: SCK provides a synchronized clock, MOSI and MISO signals are used for data transmission and reception, and /SS configures the 68HC11 as a master or slave device. RS-485 signals are used in a wide range of computer and automation systems. 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. One reason is that, large networks accumulate distributed electrical noise which can make communications unreliable. If you have not yet compiled the GETSTART program and you want to do the exercises here, open GETSTART.C in your TextPad editor, click on the Make Tool, and after the compilation is done, enter Mosaic Terminal by clicking on the terminal icon and use the "Send File" menu item to send GETSTART.DLF to the QScreen Controller.

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