5-Pin DIN MIDI Connector Pinout Guide

This guide outlines the pinout specifications for the standard 5-pin DIN cable used in MIDI connections. Although the connector features five physical pins arranged in a 180-degree arc, traditional MIDI 1.0 architecture uses only three of them to transmit digital data. Below are the precise pin assignments for the shield, positive, and negative lines, along with an explanation of how they function in a standard MIDI circuit.

Pin Assignments

On a standard 5-pin DIN connector (viewed facing the socket or solder side, where the pins are numbered 1-4-2-5-3 around the arc):

• Pin 2 (Center Pin): Shield Pin 2 connects to the cable shield (ground). In a standard MIDI configuration, this line is connected to ground at the MIDI OUT and MIDI THRU ports to provide RF/EMI shielding. It is deliberately left disconnected at the MIDI IN port to prevent ground loops.

• Pin 4: Positive (+ / Current Source) Pin 4 serves as the positive line, acting as the current source. In a traditional 5V MIDI implementation, this pin provides +5V direct current (or +3.3V in low-voltage implementations) through a 220-ohm current-limiting resistor.

• Pin 5: Negative (- / Current Sink / Data) Pin 5 serves as the negative data line, acting as the current sink. This line pulls the signal low to transmit data bits, driving the LED inside the receiving device's optocoupler.

• Pins 1 and 3: Unused Pins 1 and 3 are officially designated as "no connect" (NC) in the standard MIDI 1.0 specification and carry no signal.

How the Circuit Works

MIDI relies on a 5 mA balanced current loop rather than simple voltage levels to transfer data. At the MIDI OUT port, Pin 4 sources current through the cable to Pin 4 of the MIDI IN port. The current passes through an optoisolator's internal LED inside the receiving device, flows out via Pin 5, and returns to Pin 5 of the transmitting device to be switched on and off by a transmitter (such as a UART).

Because the signal operates as an isolated current loop and Pin 2 (Shield) is not connected at the MIDI IN receiver, the connection achieves complete galvanic isolation. This design prevents hum and noise caused by ground loops between interconnected audio equipment.