This is a module to connect MIDI signals from synthesizers or sequencers to any 3,3V powered IC or evaluation board without the need for a level shifter.

Normally MIDI runs at 5V, which makes it more difficult to interface with 3.3V equipment. This module generates 5V from the supplied 3,3V using a small charge pump. These 5V are then used to power the 6N138 optocoupler and the output buffer. Although MIDI should work with 3,3V and smaller resistors I prefer it the conventional way.

The MIDI input to the module is based on the trusty 6N138 optocoupler. The output of this coupler is pulled up to 3,3V. This is the third pin from the top.

The MIDI output uses a 5V buffer, which is 3,3V tolerant. This is the pin at the bottom.

The pinout is as follows (from top to bottom):

• 3,3V supply voltage
• Ground
• 3.3V MIDI Out. This pin carries the MIDI signals entering the MIDI-IN 5-pol jack.
• not used
• not used
• 3.3V MIDI IN. Signals routed to this pin will be transmitted using the MIDI-OUT 5-pol jack.

The pin distance is 2.0mm, not 2.54mm. You will get a fully assembled and tested module.