• 목록
• 답변
• 글쓰기
• 게시판 리스트 옵션
  • 수정
  • 삭제

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. 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. End of line termination resistor (120 ohm 1/4 watt) to be installed at both ends of network. The diagram below shows potentials of the A (blue) and B (red) pins of an RS-485 line during transmission of one byte (0xD3, least significant bit first) of data using an asynchronous start-stop method. An example of how a byte(0x3E) is transferred over the two lines of RS485 Communication. Once the bytes have been exchanged, the master may write a new byte to initiate another byte exchange. We will send some data from the transmitter side over the cable from the Nano which is converted to RS485 signals via MAX RS485 Module working in Master Mode.

The most common cable type is Cat 5e-UTP (unshielded twisted pair) which may work over shorter distances in less demanding applications with low EMI noise levels. In practice, Cat 5 cables have been used successfully in many installations, but there are some concerns. Electrical signaling is balanced, and multipoint systems are supported. It operates on a differential signaling method of measurement rather than voltage measurement wrt GND pin. Unloaded driver output differential voltage can be as high as ±6V. The complete working of this project can be found in the video linked below. 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. You need a special Ethernet cable for realizing this communication protocol.

Splicing of communications cable is not permitted. The remaining "inactive" slaves may actively receive, or listen to, data on the communications line, but only one slave at a time can transmit a message. RS-485, like RS-422, can be made full-duplex by using four wires. Most of the low-cost sensors and other modules like GPS, Bluetooth, RFID, ESP8266, etc. which are commonly used with Arduino, Raspberry Pi in the market uses UART TTL based communication because it only requires 2 wires TX(Transmitter) and RX (Receiver). There are many categories of Ethernet cables we can use like CAT-4, CAT-5, CAT-5E, CAT-6, CAT-6A, etc. In our tutorial, we are going to use CAT-6E cable which has 4 twisted pairs of 24AWG wires and can support up to 600MHz. It is terminated at both ends by an RJ45 connector. Polarity of the wires must be observed. For the transfer of data, the baud rates of both Master and Slave must be between 10% of each other.

The status of a device as master or slave determines how the various pins must be configured. If you are using the QScreen as a master device, each external SPI device will require a separate select line (/SS). Thus, the master 68HC11 has only one input, MISO, which is the slave QVGA Controller’s only output. If you do this now, remember to move the QVGA Controller’s serial connector back to Serial Port 1, and to change the terminal’s baud rate back to 9600 baud using the "Communications" item under the terminal’s "Settings" menu. Can be work well even the temperpature change suddenly. There are many different types of serial communication protocols like I2C and SPI which can be easily implemented with Arduino and today we are going to look at another most commonly used protocol called RS485 which is very commonly used in high noise industrial environments to transfer the data over a long distance. To reduce the effect of interference from external electrical signals the RS485 interface uses a differential signal over a "twisted pair" cable. The cable which I have used in the tutorial is 25m in length.

If you have any issues concerning where by and how to use what is rs485 cable, you can call us at the web site.