이름 : Clyde
이메일 : clyde_giroux@charter.net
연락처 :
예식일 : Wondering How To Make Your Rs485 Cable Rock? Read This!
문의내용:

If your application requires RS485, you can use the secondary serial port (serial2) to program and debug your application code using the RS232 protocol, and use the primary serial port (Serial1) for RS485 communications. The advantage of using Serial1 for RS485 is that the Serial1 RS485 signals are also available on the Docking Panel, while the Serial2 RS485 signals are available only on the PDQ Board’s Serial Communications Header. The Serial1 and Serial2 ports have identical communications capabilities, although more of the Serial1 signals (both RS232 and RS485) are made available on the Docking Panels headers and connectors. If there are several sensors near and/or other data to be transmitted via GSM, it is more convenient to use Standard / RF versions supported on a concentrator or controller such as RXTXeasy GSM so you will be able to use one single SIM. These protocols are summarized on this page, but for more information regarding their data formats and their use for simplex or multi-drop serial lines, consult Understanding Serial Communications (but keep in mind that that page is directed to the use of the UART Wildcard, so it uses different driver functions). Rather, it relies on software handshaking via transmission of XON/XOFF characters (ascii 0x11 and 0x13, respectively) to coordinate data transfer and ensure that information is not lost when one of the communicating parties is busy.

The PDQ Board, however, does not implement hardware handshaking. Two RS485 transceivers are present on the PDQ Board, one for each channel. It is interesting to measure the humidity of the ground, but we have also thought about other things; and then we have TXtemp to measure the temperature (one of the uses of TXtemp is in association with SuperClock), and for practically any type of measurement we have TXdata (RS232, RS485 ModBus) - which can be connected to thousands of existing third-party professional RS232 or ModBus meters (and there is something for all needs: temperature and humidity meters, anemometers, voltage meters, energy, light meters, water meters, presence sensors, brightness sensors, soil humidity sensors, etc. ; practically all professional meters are available in ModBus or RS232 standard; and not just meters). RS232 uses inverse logic; that is, a positive bit at the HCS12 UART is inverted by the onboard RS232 driver chip and appears as a negative signal on the serial cable. Killed your chip? Pop in a new one! All Screw Shields use Phoenix Contact brand screw terminals, Made in Germany, and very high quality. Builds on the original Bobuino, makes USB/Serial easier to assemble, adds lots of connection options besides just shields - signal/power/ground available at each pin location.

The ICSP header will support ICSP connectors from other shields. The pinout of the PDQ Board’s Communications Header (H2), Docking Panel’s Communications Header (H1), and the Docking Panel’s Communications DB-9 Connectors are shown in the following tables. These 9-pin standard DB-9 serial connectors are located on the back of the Docking Panel. The mating 10-pin connectors that join the H6 header of the PDQ Board to the H4 header of the Docking Panel are typically not accessed directly, and are not discussed in detail here. Thus in the table, /RTS1 is connected to /CTS1, and /DSR1 is connected to /DTR1 and /DCD1 onboard the PDQ Board using zero ohm shorting resistors. In a finished instrument, either or both channels can be used to communicate with other serial devices, rs485 cable or with other computers and/or terminals using RS232 or RS485. Two asynchronous communications ports named Serial1 and Serial2 can each be configured for RS232 or RS485 protocols. By default, the RS485 connections are not brought out to the Docking Panel’s DB-9 Serial1 Connector, although custom placement of zero-ohm surface-mount resistors on the Docking Panel can route the RS485 signals to the DB-9. The transmit and receive data signals carry the messages being communicated between the PDQ Board and the PC or terminal.

By connecting pairs of these handshaking signals together, the terminal or PC can be made to think that the PDQ Board is always ready to send and receive data. Many terminals and PCs, however, do rely on hardware handshaking to determine when the other party (in this case the PDQ Board) is ready to accept data. If handshaking is not necessary, an ordinary 4 wire telephone cable could be used, provided that the pins are cross-connected as shown in the picture below. The primary and secondary serial communications ports are accessible through the PDQ Board's 10 pin, dual row Communications Header (H2) and through the Docking Panel's 10 pin, right-angle, dual row Communications Header (H1) and individual DB-9 Serial 1 and Serial 2 connectors. Most computers conform to IBM PC AT-compatible RS232 interfaces which use 9-pin D-Type connectors, consequently the PDQ Board brings out its serial ports to two female 9-pin D-Type connectors on the Docking Panel. We can gain insight into the operation of the RS232 protocol by examining the signal connections used for the primary serial port in the above table.