How to Implement Batch Reading and Writing with Modbus TCP Using PHP

1. Introduction to Modbus TCP

Modbus TCP is an industrial communication protocol based on the TCP/IP protocol, widely used in industrial control fields, especially for data transmission between devices. By using the Modbus TCP protocol, data can be read from and written to devices in real time. This article will explain how to implement batch reading and writing using PHP with Modbus TCP, providing relevant code examples to help developers quickly achieve this functionality.

2. Environment Setup

Before writing PHP code, you first need to ensure that the necessary PHP extensions and environment are installed. Make sure that PHP is installed on the server and that Modbus TCP-related extensions are supported. After the installation is complete, you can use the phpinfo() function to check whether PHP is running properly and whether the Modbus TCP extension is loaded.

3. Modbus TCP Connection and Communication

In PHP, you can create a Modbus TCP connection using the modbus_new_tcp() function. This function requires two parameters: the IP address of the Modbus TCP server and the port number. Here’s an example of how to create a connection:

$modbus = modbus_new_tcp("192.168.1.10", 502);
if (!$modbus) {
    die('Failed to create Modbus TCP connection');
}

Once the connection is successfully created, you can use the modbus_read_input_registers() function to read data. This function requires four parameters: the Modbus TCP connection, the slave address, the register address, and the number of registers to read. Here’s an example of how to read input registers:

$data = modbus_read_input_registers($modbus, 1, 0, 10);
if ($data === false) {
    die('Failed to read input registers');
}
print_r($data);

With this code, you can read the data of the first 10 registers starting from register 0 of the device with slave address 1 and output the result.

4. Batch Reading and Writing

In real-world applications, you may need to read or write data from multiple devices simultaneously. For this, PHP provides modbus_read_input_registers_batch() and modbus_write_single_register_batch() functions that support batch operations. Here’s an example of how to read input registers in batch:

$addresses = [0, 1, 2, 3, 4];
$data = modbus_read_input_registers_batch($modbus, 1, $addresses);
if (!$data) {
    die('Failed to read input registers batch');
}
print_r($data);

Additionally, the modbus_write_single_register_batch() function can be used to write registers in bulk. It requires three parameters: the Modbus TCP connection, the device address, and an array containing the register addresses and the corresponding data. Here’s an example of how to write registers in batch:

$registersAndData = [
    [0, 100],
    [1, 200],
    [2, 300],
    [3, 400],
];
$success = modbus_write_single_register_batch($modbus, 1, $registersAndData);
if (!$success) {
    die('Failed to write single register batch');
}

With this code, you can simultaneously read and write data from a group of devices, significantly improving data processing efficiency.

5. Conclusion

As shown in the examples above, implementing batch reading and writing with Modbus TCP using PHP is straightforward and efficient. With the right development environment and the appropriate Modbus TCP PHP extension functions, you can easily achieve communication and data manipulation between devices. I hope this article helps you better understand and use the Modbus TCP protocol to enhance the data processing capabilities of industrial control systems.