AN-960: RS-485/RS-422 Circuit Implementation Guide > 자유게시판

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RS-485 does not specify any protocol, addressing scheme, RS485 standard or connector. This defines all 25 pins of the connector. Library initializes and defines a GPIO driver and performs control of device voltage. RS485 is a standard that defines the electrical characteristics of drivers and receivers used in balanced digital multipoint systems. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. The full application code and ready to use projects can be found on our LibStock page. The terminal available in all MIKROE compilers, or any other terminal application of your choice, can be used to read the message. We provide a demo application for the RS485 click 5V click on our LibStock page, as well as a demo application (example), developed using MIKROE compilers. The demo can run on all the main MIKROE development boards. Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board.

It is a tristate differential line driver and differential input line receiver intended to be used as a physical layer device, often called PHY, providing physical interfacing of the MCU TTL level UART lines with the RS422/485 bus. These jumpers enable bus biasing by using pull-up and pull-down resistors between the bus differential lines and VCC/GND, respectively, preventing certain faulty conditions when no drivers are enabled on the bus, in addition to existing IC protection. However, the bus length determines the maximal transfer speed: longer bus lines will result in less transfer speed. In this state, the differential voltage between lines A and B is zero. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. The RS485 standard prescribes using a twisted pair cable as the data bus. It is well suited for transmitting smaller data blocks over long distances, using a twisted differential signal pair for both TX and RX signals, allowing for half-duplex asynchronous communication.

2. Scalability: Through RS485, PLC can communicate with numerous devices over long distances, making it scalable to accommodate growing industrial operations. PLC is the core of industrial automation. Modbus RTU and Modbus TCP are prevalent in industrial automation. 1. Robustness: RS485’s robustness to noise and interference ensures that the PLC receives accurate data for decision-making, thereby reducing the chance of errors in the automation process. Twisted pair cable tends to cancel common-mode noise and cause cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair. This helps to limit the current through the "third" wire. The temperature sensor DS18B20 is a digital temperature sensor, because to transmit the information it uses the protocol 1 - Wire. It is mainly used for sending data in ordinary networks through 2 to 4 wire mode. Four-wire networks consists of one master with its transmitter connected to each of the slaves' receivers on one twisted pair. It is generally used between one transmitter receiver pair to ONLY one other transmitter receiver pair but each output can drive up to 10 receivers. When a HIGH logic level is applied to the R/T pin, the transmitter becomes activated, while the receiver is deactivated at the same time - and vice versa.

The R/T pin acts as a communication direction pin in this configuration. Receiver output enable (RE) and driver output enable (DE) pins of the ADM485 are joined together and routed to the R/T pin of the mikroBUS™ socket. Therefore, RS485 click 5V offers UART RX and TX pins routed to the appropriate mikroBUS™ TX and RX UART pins. This table shows how the pinout on RS485 click 5V corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns). This figure shows biasing applied to the termination network. With no driver connected, the differential voltage on the wires will depend on the termination resistor and biasing. The Click board™ is equipped with a jumper that can be used to route the termination resistor of 120Ω between the bus lines. RS485 Click 5V uses a standard 2-Wire UART interface to communicate with the host MCU with commonly used UART RX and TX lines. The signal will eventually stabilize (until the next bit transition) so the slower the bit rate the more time the signal will have to stabilize before it is sampled (usually by a UART).