How to implement Modbus TCP data reading and writing through PHP

How to implement Modbus TCP data reading and writing through PHP

Modbus is a commonly used communication protocol used to communicate between devices in the industrial field. Modbus TCP is a variant of the Modbus protocol that uses the TCP/IP protocol to communicate on the network. In this article, we will introduce how to read and write Modbus TCP data through PHP.

1. Install Modbus PHP extension
   Before using PHP to implement Modbus TCP communication, we need to install a Modbus PHP extension. A commonly used extension is phpmodbus, you can download its code at https://github.com/angeloc/phpmodbus and copy the code into your PHP project.
2. Establishing a Modbus TCP connection
   It is very simple to establish a Modbus TCP connection using the phpmodbus extension. First, we need to create a ModbusMaster object and specify the IP address and port number of the Modbus server. Examples are as follows:

require_once('modbus/ModbusMaster.php');

$modbus = new ModbusMaster("192.168.1.1", "TCP");

3. Read Modbus data
   Modbus protocol supports multiple methods of reading data, such as reading holding register (Holding Register) and input register (Input Register) , coil (Coil), etc. We can use the readMultipleRegisters() method of the ModbusMaster object to read the data of the holding register. An example is as follows:

$startAddress = 0;
$length = 10;

$data = $modbus->readMultipleRegisters(1, $startAddress, $length);

for ($i = 0; $i < $length; $i++) {
    echo "寄存器 " . ($startAddress + $i) . " 的值: " . $data[$i] . "
";
}

4. Write Modbus data
   If we want to write data to the Modbus server, we can use the writeSingleRegister() or writeMultipleRegisters() method of the ModbusMaster object. An example is as follows:

$address = 1;
$value = 123;

$modbus->writeSingleRegister($address, $value);

echo "写入成功
";

5. Error handling
   In practical applications, we need to perform error handling on Modbus communication. Each method of the ModbusMaster object returns a Boolean value indicating whether the communication is successful. If communication fails, we can use the getError() method to obtain error information. An example is as follows:

if (!$modbus->writeSingleRegister($address, $value)) {
    echo "写入失败：" . $modbus->getError() . "
";
}

To sum up, we can use PHP to read and write Modbus TCP data by using the phpmodbus extension. By establishing the ModbusMaster object and choosing the appropriate method, we can easily perform Modbus communication. Paying attention to error handling can improve the stability and reliability of the program.

Although this article only provides the basics of implementing Modbus TCP in PHP, it provides you with a good starting point so that you can further learn and develop more complex Modbus applications. I hope you can continue to explore and learn in practice and give full play to the potential of Modbus!

The above is the detailed content of How to implement Modbus TCP data reading and writing through PHP. For more information, please follow other related articles on the PHP Chinese website!