How to parse and process Modbus TCP response messages in PHP

How to parse and process Modbus TCP response information in PHP

Overview:
Modbus is a communication protocol used to transmit data in industrial control systems. Modbus TCP is an implementation of the Modbus protocol, which transmits data based on the TCP/IP protocol. In PHP, we can use some libraries to parse and process Modbus TCP response information. This article will explain how to use the phpmodbus library for parsing and processing.

Install the phpmodbus library:
First, we need to install the phpmodbus library. It can be installed through Composer using the following command in the project:

composer require php-modbus/php-modbus

Parsing Modbus TCP response information:
After sending the Modbus TCP request, we will get a response containing the requested data. To parse this response we can use the ModbusMaster class from the phpmodbus library.

First, we need to instantiate the ModbusMaster class and specify the IP address and port number of the Modbus TCP device to be connected:

<?php
require_once 'vendor/autoload.php';

use PHPModbusModbusMaster;

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

Then, we can use the readMultipleRegisters method of the ModbusMaster class to read Data in Modbus register. This method accepts 3 parameters: device ID, register address to be read, and number of registers to be read. The response returned will contain the requested data.

$deviceId = 1;
$startAddress = 0;
$quantity = 10;

$response = $modbus->readMultipleRegisters($deviceId, $startAddress, $quantity);

Processing Modbus TCP response information:
Once we get the Modbus TCP response, we can process it. In the response, the data is returned as a 16-bit integer. This data can be decoded using the decodeRegister method of the phpmodbus library.

$data = $response['data'];
$decodedData = $modbus->decodeRegister($data);

The decodeRegister method will return an array containing the decoded data.

We can also use other methods of the phpmodbus library to handle Modbus TCP responses. For example, if you want to read the value of a single register, you can use the readSingleRegister method. Similarly, we can use the writeMultipleRegisters method to write the values ​​of multiple registers. We can call these methods appropriately in our code as needed.

Full sample code:
The following is a complete sample code that demonstrates how to parse and process Modbus TCP response information in PHP using the phpmodbus library:

<?php
require_once 'vendor/autoload.php';

use PHPModbusModbusMaster;

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

$deviceId = 1;
$startAddress = 0;
$quantity = 10;

$response = $modbus->readMultipleRegisters($deviceId, $startAddress, $quantity);

$data = $response['data'];
$decodedData = $modbus->decodeRegister($data);

foreach ($decodedData as $value) {
    echo $value . "
";
}

?>

Summary:
Parsing and processing Modbus TCP response messages in PHP can be achieved by using the phpmodbus library. We can use the ModbusMaster class to parse and process Modbus TCP responses. By using readMultipleRegisters, decodeRegister and other related methods, we can read and process data in Modbus registers. Hopefully this article will help you understand how to parse and process Modbus TCP response messages in PHP.

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