Transmit RS485 Data over Ethernet > 자유게시판

The transmitter and receiver compare the voltages of the data- and handshake lines with one RS485 standard common zero line. Line A voltage, implying A, the green wire, is indeed connected to the driver inverting signal, as seen in a whitepaper. If more than one driver needs to be connected on the same bus, then RS-485 is recommended. Both are multi-drop, and both can communicate via very long distances, so then why choose one over the other? Over the years, various serial communication protocols have gained priority. The receivers use low offset bipolar differential inputs, combined with high precision resistor dividers to maintain precise receiver thresholds over the wide common mode voltage range. RS-485 requires the driver and receiver to function if the common mode voltage is shifted against circuit common (see the section on voltages for more information). Even though the logic function of the generator and receiver are not defined by RS-485, it makes sense to many engineers to have a binary 1 appear on the RS-485 wires when a binary 1 is being transmitted.

For normal logic when the input of a driver is a 1 or high, the non-inverting output will go high. But, since one of outputs goes high when the input goes high, it is often called the "non-inverting" output. This is exactly what is expected from the symbol of RS-485 figure 1, and exactly backwards from what is expected based on the signaling waveform of RS-485 figure 1, because this driver does not invert its input. The MAX3485 interface chip is an RS-485 driver chip from Maxim. This is the reason why RS-485 transceivers must have driver/receiver enable pins enabling only one driver to send data at a time. RS-485 functions by defining the transmission of ‘0’s and ‘1’s via the positive or negative states of the transceiver terminals, A and B. To perceive the same logical state, all devices on the communication link must generate and detect signals of the same polarity.A reversed device will read and generate incorrect signals, leading to a communication breakdown.

Application software accesses the USB device in the same way as it would access a standard Windows Com Port using the Windows VCOMM API calls or by using a Com Port Library. Half of the conductors in a 50 way cable are ground return wires. 3. Noise Resistant - Since it uses a separate FLOATING transmit and receive pair (four wires), it offers better noise immunity than RS232. Shielding-which is a common method to prevent noise in RS232 lines-tries to keep hostile magnetic fields away from the signal lines. A circuit is a full definition of a signal from the transmitting device to the receiving device, but many now think of these definitions as pin labels. 3. Not Multi-drop - You can only connect one RS232 protocol device per port. Any data that arrives on the RS485 bus will be transmitted via the USB port to the PC. During such periods, the bus may exhibit a 0-V differential signal due to the presence of a termination resistor. Transmission lines should always be properly terminated, with short stubs, to prevent signal reflections. Although this is your domain, it's always helpful to have a little starting point, so we've put together a couple of short articles on using the PC Serial Com.

2. Multi-Drop - Usually, up to 32 devices can be connected per port, and even more using repeaters. After installing the drivers, and plugging in the USB-RS485 module to a spare USB port, you will want to know which COM port it has been assigned to. You should get and install the drivers now, before you connect the USB-RS485 to your computer. The USB-RS485 supports data rates of up to 250kbps (bits). When the PC transmits data the bus direction immediately turns around to transmit the data out on the RS485 bus. The drawing below illustrates connection of a BMS directly onto the DyNet bus. RS485 to Ethernet Converters have a physical wired or wireless (LTE or WiFi) network connection on one side, and one or more RS485 serial ports on the other side. One RS-485 network can be used for the master to talk to all of the slaves on the network, and a different RS-485 network can be used for all of the slaves to talk back to the master.

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