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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. If you keep the cable length at 70% or 80% of this limit you should expect the network to work with a true RS-232 driver and receiver. If you have a nice-looking shielded twisted cable that doesn't have its impedance stated, you can find out yourselfs (see my reflectoprobe suggestions above) - you will likely measure something between 60 and 80 Ω diff-mode, and consequently 15-20 Ω common mode. It works in full-duplex mode and requires three wires: ground, transmit and receive. On the other hand, RS-422 commonly supports full-duplex operation, allowing for simultaneous transmission and reception of data. 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.

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. The TCP/IP protocol must belong to the network layer and the transport layer. Expanding the capabilities of the RS232 standard was the impetus for developing the RS485 protocol. At CO2Meter we regularly field questions about using the RS485 protocol. 5.Because the RS485 interface has good anti-interference ability, long transmission distance and multi-station capability, it becomes the preferred serial interface. RS232 Serial Port: A serial port for communication between devices. 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. 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. The CONV-USBTORS232/485 module derives the power from the USB port and doesn't need any power adapter.

Making effective use of serial devices often involves converting between RS232, RS485, and USB signals. D405 is a Schottky diode used to allow the board's 5 V and 3.3 V circuits to be powered via USB. 3.The two-wire RS485 can only work in a semi-duplex mode, and the sending and receiving cannot be carried out at the same time. The four-wire system is rarely used now, and now the two-wire system is mostly used. 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). In the RS485 interface, when organizing a network, a microcircuit that transmits information is called Master, and the one that receives information - Slave. However, with the rapid development of today's science and technology, a large amount of information and communication data increases, RS485 standard and the requirements for distance are also increasing.

However, TCP/IP is as simple as recv() and send(). However, in different physical layers, it is divided into TTL serial port, RS232 serial port, RS485 serial port and so on. Instead, the questions we often receive are about sensors and devices that have standard serial UART (Rx/Tx) or I2C communications protocols on the spec sheet. Commercial aircraft cabins also use RS485 for low-speed data communications. It is important to implement remote control and other requirements where serial ports must be tightly connected with Ethernet or fiber optic communications. Today, many devices use serial communication, especially in industrial automation and security monitoring projects. This means that data can be simultaneously transmitted and received between devices. It is not a simple conversion between the physical layer and the data link layer. For example, the user passes The recv() function and send() function of the socket send and receive data that is actually the application layer. In general, a serial port is a UART, and actually only defines the data link layer specification, namely start bits, data bits, and stop bits. Therefore, the serial port for TCP/IP is incorrect. The RS232 master port can be jumper configured as DTE or DCE. PURPOSE AND SCOPE OF COVERAGE - This standard is applicable to the interconnection of data terminal equipment (DTE) and data circuit-terminal equipment (DCE) employing serial binary data interchange.