Much like RS232, RS485 doesn’t have an actual standard connector. RS422 can have only one Commander and multiple Listeners. RS485 is a half duplex version of RS422 that is capable of multi-drop operation. To use a QScreen as a slave in a multi-drop network, simply define a word, (named Silence(void), for example) that when executed calls RS485Receive() to wait for any pending character transmission to complete, then disable the transmitter, and then execute a routine such as Key() to listen to the communications on the serial bus. Problem solved thanks to RS485 communications. Let’s talk about what we now know about RS485. If you are familiar with RS232, then you may already know a little bit about it. RS232 data is sent serially, each bit is sent one after the next because there is only one data line in each direction. RS-485 is a serial communication protocol, which means that data is transmitted one bit at a time over a single communication channel.28. RS232 could only handle one at a time. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol.
The Serial 1 port can be configured for either RS232 or RS485 communications at up to 19200 baud. What made it such an advancement over RS232 was the fact that it could transmit not only a single device to device transmission, but also a communications bus to connect multiple devices at once. A FIFO is a First In/First Out buffer that can queue a burst of outgoing characters for transmission, or save a set of incoming characters until the host can read them. One example of such cable is Belden 3105A. But any cable with similar characteristics can be used to connect all the devices together. One very common example in the automation world is remote control of VFDs or Variable Frequency Drives. Many people just call them motor drives. Note that the local and the remote must share a common ground, so a minimum of 5 wires are required for full duplex RS422 communications: two transmit wires, two receive wires, and a common ground. In other words, each local UART on the wildcard can both send data to and receive data from a remote UART on the other end of a connecting serial cable. Although the maximum standard baud rate of the primary serial port is 19200 baud, nonstandard baud rates of over 80 Kbaud can be attained by the 68HC11's on-chip UART and the onboard RS232 driver.
The maximum cable length for RS232 communication is 50 feet. The maximum RS485 cable length is typically listed as 1200 meters or about 4000 feet. Users can utilize a longer cable, up to 1200 meters or 4000 feet. With your RS485 network, you can remotely monitor and control that pump from a control center. All of this allows you to speed up the VFD that controls the speed of that water pump. Let’s say you were monitoring a water pump filling a vessel. The PLC is programmed to monitor the level of the water in the vessel. It is important to use the right level of detail when working with a wiring diagram. Q: How do RS485 wiring and cable requirements differ from RS232? By having access to a wiring schematic, and understanding it, an individual will be able to quickly diagnose issues with the RS232 to RS485 cable. Another advantage over RS232 that I mentioned earlier is the number of connectable devices. RS232 has an advantage when short-distance and low-speed are required. It is faster and much more versatile than the older RS232.
Here at Seeed, we believe that the Internet-of-Things (IoT) will be a new class of digital and physical infrastructures that will allow a more intelligent society. Designed with industry standards, it comes with a waterproof aviation connector to ensure that your connection will not be affected by the elements. Many times the old DB-9 connector is used. Most manufacturers still utilize a DB-9 connector. The RS485-ISO adapter provides electrically isolated conversion from RS-232 on the main 7W2 connector to RS-485. Their main difference boils down to one having only support for RS485, while the other one supports RS232 and TTL as well. RS232 could only handle one. You aren’t limited to fifty feet of cable like with RS232. Belden RS-485 Cable options have low capacitance and perform well over long distances, making them an ideal choice for industrial automation applications. Many communication protocols have been designed to achieve data exchange.