Using PHP to Communicate with MIDI Devices via Serial Port

With the advancement of music technology, many devices now support the MIDI (Musical Instrument Digital Interface) protocol, which enables communication and interaction between instruments from different manufacturers. This article explains how to use PHP to communicate with MIDI devices and provides a complete code example.

MIDI is a digital communication protocol that defines the data format and transmission method between musical equipment. A MIDI message consists of three bytes: a status byte that indicates the type of message, and two data bytes that carry the actual information (e.g., 0x90 for “Note On”, 0x40 for velocity).

To communicate with a MIDI device from PHP, we can use a serial‑port communication extension. The following example demonstrates opening a serial port, configuring it for the standard MIDI baud rate (31250 bps), and sending a simple “Note On” message.

<?php
// Open serial communication
$serial = new PhpSerial();

$serial->deviceSet("/dev/ttyUSB0");
$serial->confBaudRate(31250);
$serial->confParity("none");
$serial->confCharacterLength(8);
$serial->confStopBits(1);
$serial->confFlowControl("none");

$serial->deviceOpen();

// Send MIDI message
$statusByte = 0x90; // Note On
$dataByte1 = 60;    // Middle C
$dataByte2 = 127;   // Maximum velocity

$message = pack("C*", $statusByte, $dataByte1, $dataByte2);
$serial->sendMessage($message);

// Close serial communication
$serial->deviceClose();
?>

The code first creates a PhpSerial instance, sets the device name, baud rate, parity, character length, stop bits, and flow control, then opens the port. The sendMessage method transmits the packed MIDI bytes, and finally deviceClose releases the port.

In practice the example can be extended: you may write functions to send different types of MIDI messages, receive incoming messages, and add error‑handling logic to ensure stable communication.

In summary, by using PHP together with the MIDI protocol you can achieve communication with musical hardware; the provided sample code shows the basic steps for sending a MIDI “Note On” message.

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