9-pin serial line production, DB9 Series Port Connection
Keywords: serial line production, computer serial line production
At present, there are 9-pin serial port (DB9) and 25-pin serial port (DB25). When the communication distance is closer (<12m), the standard RS232 port (RS422, RS485) can be directly connected to the cable (RS422, RS485 farther), if distance Far, additional modems are required. The most simple and commonly used is three-line interface, that is, the reception data and the transmission data are connected three flops. The same serial port is connected to the transmitting foot and the transmitting foot is connected to the 9-pin serial port and 25-pin serial port, both 2 and 3 are directly connected; two different serial ports (whether two serial ports of the same computer are different computers Serial port) The received data pin (or line) is connected to the transmitted data pin (or line), intersecting each other, and the signaling corresponds to each other.
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The joint can be divided into male heads and bodies: the public generally refers to the needle connector; the mother is generally referring to the socket joint. The pin of all connections is unified, and there is a printed serial number on the connector, pay attention to view when connecting. The needles that are not mentioned during wiring are suspended. Be
Serial port
25-pin serial function list pin function 2 Send Data (TXD) 3 Receive Data (RXD) 4 Send Request (RTS) 5 Send Clear (CTS) 6 Data Preparation (DSR) 7 Signal (GND) 8 Serial Detection (DCD) 20 Data Terminal Ready (DTR) 22 Ringing Indication (RI)
9-pin serial function list pin function 1 carrier detection (DCD) 2 Receive data (RXD) 3 Send data (TXD) 4 Data terminal ready (DTR) 5 Signal (GND) 6 Data Preparation (DSR) 7 Send request ( RTS) 8 Send Clear (CTS) 9 Ringing Indication (RI)
I need to make a two-headed lines of public, used to connect GPRS and development boards. The connection method is:
1-1, 2-3, 3-2, 4-4, 5-5, 6-6, 7-7, 8-8, 9-9. That is, 2, 3, other direct connection.
The relationship with the color and the pin: (I don't know if there is versatility, huh, huh)
1 black, 2 brown, 3 red, 4 orange, 5 yellow, 6 green, 7 blue, 8 purple, 9 white.
Serial Port Control In Serial Communication Processing, often see two options of RTS / CTS and XON / XOFF, which is the two stream control options, and current flow control is mainly applied to the data communication of the modem, but for ordinary RS232 programming, understanding the knowledge in this area is good. So, what is the role of streaming in serial communication? What is the application of serial communication programs? 1. Flow Control The role in serial communication This "stream", of course, is a data stream. When the data is transmitted between two serial ports, there is often a phenomenon of loss of data, or the processing speed of the two computers is different, such as communication between the desktop and the microcontroller, the receiving end data buffer is full, then continue to send The data coming will be lost. Now we have data transmission through MODEM on the network, this problem is particularly highlighted. Flow control can solve this problem, when the receiving end data processing is not, "no longer receiving" signal is issued, the sending end stops transmission until the "can continue" signal will be sent again. Therefore, stream control can control the process of data transmission to prevent data from loss. Two stream controls commonly used in the PC are hardware flow controls (including RTS / CTS, DTR / CTS, etc.) and software flow control XON / XOn / XOn / XONFF (continued / stop), which will be described below. 2. Hardware flow controls hardware flow control commonly used RTS / CTS stream control and DTR / DSR (Data Term Read Read Read Read Ready) Flow Control. Hardware flow control must connect the corresponding cable, and use RTS / CTS (request send / clear transmission) stream to control the RTS, CTS lines on both ends of the communication, and the data terminal device (such as a computer) uses RTS. Start the data stream of the demodulator or other data communication device, and the data communication device (such as a modem) is started with CTS to start and suspend traffic from the computer. The process of this hardware handshake mode is: We set a high-level flag according to the receiving end buffer size when programming (75% of the buffer size) and a low mark (25% of the buffer size), when buffer When the data volume in the zone reaches a high position, we set a low level (send logic 0) at the receiving end. When the sender's program detects that the CTS is low, the transmission data is stopped until the data amount of the receiving end buffer is low. The CTS is high at a low position. RTS is used to indicate whether the receiving device is ready to receive data. Common stream controls have DTR / DSR (Data Terminal Ready / Data Setting Ready). We will not be detailed here. Due to the diversity of stream control, I personally think that when using flow control in the software, you should do a detailed description, how to connect, how to apply. 3. Software flow control Due to the limitations of the cable, we generally do not have hardware flow control in ordinary control communication, and use software flow control. Software flow control is generally achieved by XON / XOFF. The common method is: When the amount of data in the input buffer in the receiving end exceeds the set high position, the xoff character (decimal 19 or control-s, the device programming manual should be described in detail), the transmitting end is received After the Xoff characters, the XOF characters immediately stop sending data; when the amount of data in the input buffer in the receiving end is lower than the set low position, the XON character (decimal 17 or control-q) is sent to the data sender, and the sender receives Xon characters. I started to send data immediately. It is generally possible to find what characters sent from the device supporting source program. It should be noted that if binary data is transmitted, the flag character may also occur in the data stream, which is the defect of software flow control, and hardware flow control does not have this problem.
RJ45 turn DB9
Just do 3 lines.
RJ45 side: DB9 side:
3 --- 2 4 --- 56 --- 3
Serial number of RJ45:
____| -------- || 12345678 || || || || -------- | | | | | | | |
DB9 (female / female) serial number:
\ ------------- / \ 5 4 3 2 1 / \ 9 8 7 6 / ---------
Remarks: If you want to measure with a multimeter, you can put a needle or a head in the hole of DB9.
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