What is the purpose of the RS-485 Interface?
RS-485 is an industrial specification that defines the electrical interface and physical layer for point-to-point communication of electrical devices. The RS-485 standard allows for long cabling distances in electrically noisy environments and can support multiple devices on the same bus.
How to use RS485 to send and receive data?
Connect jumper cap W1 and W2 to use RS485 to send and receive, not to connect is common serial port transceiver. RE and DE are transceiver enabled, 485 mode is selected: 3_ When sending data, the start bit (falling edge) of the data will be 3_ When the TXD pin level is pulled low, it will enable sending.
Are there any standards for RS485, RS232, and RS423?
The Electronics Industry Association (EIA) has produced standards for RS485, RS422, RS232, and RS423 that deal with data communications. Suggestions are often made to deal with practical problems that might be encountered in a typical network.
What is the impedance of a RS-485 cable?
Industrial RS-485 cables are of the sheathed, unshielded, twisted-pair type, (UTP), with a characteristic impedance of 120 W and 22–24 AWG. Figure 4 shows the cross-section of a four-pair, UTP cable typically used for two full-duplex networks.
How does a RS-485 UART work as a half duplex?
UART having dedicated transmit and receive lines allows it to operate as full-duplex, half-duplex, or even simplex, which means data only ever goes out or comes in on one line. Since RS-485 is typically half-duplex, the UART connected to it will also operate at half-duplex.
How does the RS-485 transceiver work on a slave?
The slave system is identical, meaning that the slave RS-485 transceiver receives the incoming bitstream, converts it to a single ended signal, and sends it to the host device via the slave’s UART RX line. When the slave is ready to respond, it transmits as the host did originally while the host now receives, Figure 9.
What kind of differential voltage is required for RS-485?
The bus requires a minimum differential voltage of +/- 200 mV at the receiver and generally all RS-485 devices will have the same input voltage range despite transmitting at various voltages.