How to implement serial communication through PHP and RS232 protocol

How to realize serial communication through PHP and RS232 protocol

Overview:
Nowadays, serial communication is widely used in many fields, such as industrial automation, communication equipment, etc. This article will introduce how to use PHP language to communicate with the serial port through the RS232 protocol, and provide relevant code examples.

Introduction to RS232 protocol:
RS232 protocol is a commonly used serial communication protocol, which defines the standards for the physical layer and data link layer of serial communication. Through the RS232 protocol, we can transmit data between the computer and external devices, such as sensors, PLC, etc.

How PHP communicates with RS232:
To use PHP language to communicate with the serial port, we need to use the PHP extension library php_serial. php_serial is an open source extension library that encapsulates the serial communication function into a PHP class library.

The steps are as follows:

1. Make sure the system supports serial port communication
   Before using php_serial, you must first ensure that the system's serial port device is working properly. You can use the terminal command ls /dev/tty* to view the serial devices available in the system.

2. Install the php_serial extension library
   You can install the php_serial extension library through the following command:

   sudo apt-get install php-pear
   sudo pecl install channel://pecl.php.net/php_serial

   After the installation is completed, you need to add the following configuration to php.ini:

   extension=php_serial.so

3. Introduce the php_serial class and create the serial port object
   In the PHP code, we can introduce the php_serial class through the require_once keyword and create the SerialPort object:

   require_once('php_serial.class.php');
   $serial = new phpSerial;

4. Set serial port parameters
   Before communicating with the serial port, you need to set the parameters of the serial port, such as baud rate, data bits, parity, etc. You can use setPort, setParity, setDataBits and other methods to set the serial port parameters:

   $serial->setPort("/dev/ttyUSB0");
   $serial->setBaudRate(9600); //设置波特率为9600
   $serial->setParity("none");
   $serial->setDataBits(8);
   $serial->setStopBits(1);
   $serial->setFlowControl("none");

5. Open the serial port
   After setting the serial port parameters, you can open the serial port through the open method:

   $serial->open();

6. Read and write serial port data
   The data received by the serial port can be read through the readPort method:

   $read_data = $serial->readPort();

   The data can be sent to the serial port through the writePort method:

   $serial->writePort("Hello World!");

7. Close the serial port
   After the communication is completed, remember to close the serial port:

   $serial->close();

   The complete PHP code example is as follows:

   require_once('php_serial.class.php');
   
   $serial = new phpSerial;
   $serial->setPort("/dev/ttyUSB0");
   $serial->setBaudRate(9600);
   $serial->setParity("none");
   $serial->setDataBits(8);
   $serial->setStopBits(1);
   $serial->setFlowControl("none");
   
   $serial->open();
   
   $serial->writePort("Hello World!");
   
   $read_data = $serial->readPort();
   
   $serial->close();

   It should be noted that the serial port communication is in Linux It is slightly different from the implementation in Windows systems and can be adjusted accordingly according to the system type.

Conclusion:
Implementing serial communication through PHP and RS232 protocol can bring more possibilities to our projects. In practical applications, we can flexibly adjust the serial port parameters according to specific requirements to achieve data interaction with external devices. I hope this article can be helpful to readers and trigger more exploration and practice.

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