RS485: more on Transmission Line Termination & Material + Reality Chec…

Since the serial port protocol itself has no network layer and transport layer, the data to the Ethernet serial port actually uses the serial port data as TCP/IP application layer data, and uses the TCP/IP packet forwarding method. Serial port for data communication between MCU chips. If divided into ISO's 7-layer model (physical layer, data link layer, network layer, transport layer, session layer, presentation layer, application layer), the serial port actually only includes the physical layer and data link layer. From serial port to network port and from network port to serial port, because these products can convert both ways, it is actually the same. The questions are not about devices that have actual RS485 ports like our MX, EX, RS485 standard TX and package products which communicate over lines labeled A&B with Rx (receive) and Tx (transmit). The Over IP serial type is used to manage serial connections over a TCP/IP network.

For multiple connections they cannot use I2C as it is distance limited to about 1 meter. In the absence of a computer, a single Laureate meter with an L485 RS485 board can drive multiple Laureate 6-digit remote displays. 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. Although this voltage may be insufficient to switch the receiver state directly, an internal bias current within the attenuation network creates a voltage difference at the receiver comparator input. It is normally in listen (or receiver) mode. 2) The RS485 interface adopts a combination of a balanced driver and a differential receiver, which has strong anti-common mode interference capability, that is, good anti-noise performance. 1) The signal level of the interface is relatively high, and the chip of the interface circuit is easily damaged. 1.The interface signal level is relatively high, and the interface circuit chip is easily damaged. 3) The standard value of the maximum transmission distance of the RS485 interface is 4000 feet, which can actually reach 3000 meters. Optimum impedance for RS485 is 120 Ω (expected by the line drivers).

RS485 is a standard defining the electrical characteristics of drivers and receivers for use in serial communications systems, widely used in the industrial field. There are however lower-grade "fire-resistant" cables matching the general "shielded twisted pair" specification, for basic signaling applications, which can also be used for RS485 for shorter distances. For RS485, the impedance of just 70 Ω may prove a tad too low for longer distances. It is possible to connect several RS485 circuits in parallel if the distances are below about 200 feet per leg @ 9600bps. At greater distances and higher data rates, the cable impedances add up and load the network. RS232 is a two-wire, asynchronous serial communication protocol that uses voltage levels to transmit and receive data. Two serial protocols are user-selectable for RS485: Modbus RTU and Custom ASCII. Other features include an HDMI port, two USB Type-A ports, and a USB Type-C 2.0 port.

Depending on the action mode, it is related to connection, shutdown, monitoring, etc. This is the part that needs to be dealt with after converting the serial port to a network port. RS485 serial port communication is very convenient for multi-point interconnection, and many signal lines can be saved. To show you how simple this is, I wired up a K-30 CO2 sensor to communicate with our free GasLab software via RS485 in a few minutes from stuff on my desk, zero software, in between some other projects. When the four-wire system is used, only point-to-multiple communication can be realized (that is, there can only be one master device, and the rest are slave devices). 2) The RS485 interface adopts a combination of a balanced driver and a differential receiver, which has strong anti-common-mode interference ability, that is, good anti-noise performance. 2V. The interface signal level is lower than that of RS-232-C, so it is not easy to damage the interface circuit chip, and this level is compatible with TTL level, which is convenient for connection with TTL circuit. The voltage of any signal line of the RS-232 interface is a negative logic relationship.