Includes 52 Functions Plus Modem Control > 자유게시판

RS-422 specifies a number of other things, but they are all electrical values. The capacitor values are a balance between current consumption and ESD suppression, with 470 pF being a nice middle ground. Make sure power traces and fills are large enough to accommodate the expected current. Many other IC manufacturers make a drop-in replacement for this IC, and many of them (such as the MAX483) use the same labeling. 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. This allows RS-485 to implement linear bus topologies using only two wires. 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. Any data that arrives on the RS485 bus will be transmitted via the USB port to the PC. Similarly, with activity on the other pair, we know that data is flowing from the external hardware to the PC.

In general if you are not connected to a modem the handshaking lines can present a lot of problems if not disabled in software or accounted for in the hardware (loop-back or pulled-up). USB serial devices, scales, GPS navigation, etc. The component library includes 52 functions plus serial line status & control, modem control, XMODEM and YMODEM, ASCII and ANSI terminal emulation. That being said, what is the practical line length limit? Low capacitance cable becomes important when pushing line length and/or data rates to the maximum. Onboard unibody digital isolation, allows signal isolation, high reliability, strong anti-interference, and low power consumption. Introduction SE509-PT1000 ultrasonic energy meter, which is used for measuring individual energy consumption in any liquid heating/cooling systems. Drivers are available for Windows, Apple, Linux and Open BSD systems directly from the FTDI website. The documentation provided by FTDI is very complete, and is not duplicated here. The USB-RS485 module uses the FTDI FT232R USB chip to handle all the USB protocols. Keep the QSPI traces to the flash chip (U302) relatively short and avoid crossing layers. To keep things simple, I went with the same transciever IC used in the Lumen motherboard, the MAX3078E.

Keep in mind that all three are considered SERIAL, as opposed to IEEE-488 which is PARALLEL . Thus, two ICs are used where U6 is set up to receive data from the PC and U7 is set up to transmit data to the PC. When the driver increases the voltage on one of the wires, it simultaneously decreases the voltage on the other wire resulting in a differential voltage between the two wires. 3. Programming RS485 is more difficult, since you are sending and receiving on the same two wires, you need to enable and disable the transmitter at the correct time so that you may perform proper communications. When programming an RS485 plug-in card, you would read the STATUS REGISTER to determine if it is time to switch or not. This is handled by the 7-segment DIP switch feeding directly into the PIC16F877. There are no command structures, whatever is sent to the Virtual Comm Port is automatically converted to RS485 and vice versa. 0.2V the receivers output switches to a 1 and when the voltage goes below -0.2V the receivers output switches to a 0. (or vice versa if there is inversion on the receiver) Since the last bit from a UART will be the stop bit (1), then the transmitter is turned off (the differential voltage goes to 0V, but not having gone less than -0.2V), this should leave the receiver with a 1 being output to the receiving UART.

Circuit designers will be quick to observe that RN12 is not really required because the high output of the latch would turn on Q1 independent of having RN12. The exact voltage level that a logic device considers ON or OFF varies by logic type, but when the voltage is high (usually but not always approaching the IC's supply voltage), the output is on and a binary 1 is on the wire, and when the voltage is approaching 0 the output is off and, a binary 0 is on the wire. Devices are distinguished by unique addresses that are assigned to each device. With RS485, you can have multiple PC's and multiple controllers on one bus, so that one PC can send a command to change a setpoint,and another PC can send a command to send back data, etc. Remember that all devices on the bus must have a unique unit address, so that only the addressed unit will respond. If you want to change the COM port number - just right click on it, select properties, select advanced and select the COM port number from the available list. However, things may soon change for obvious reasons.

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