Nextion MIDI I/O interface

The Nextion MIDI I/O interface is a TTL serial to 5 pin DIN MIDI input and output converter with pass-through function for easy connecting with but not limited to Nextion HMI displays. The level conversion between TTL serial and MIDI is done with a specific driver IC for MIDI OUT and with an isolated optocoupler for MIDI IN. Integrated line filters allow the use of long MIDI cables, even in EMI intensive environments, for example in studios or on stage. Features: Two 4 pin XH connectors for 5V power supply, TX, RX and GND allow this interface to be easily daisy-chained between either a power supply / USB to TTL serial adapter like the Nextion Foca Max, or any MCU (Arduino, etc.) on one side (J1) and a Nextion HMI display on the other side (J2). The on-board switch SW1 allows to select between 2 modes:

• PRGM: RX + TX signals are directly routed from J1 to J2 which allows to program the device on J2 by the device on J1 while the MIDI interface is idle. 
• MIDI I/O: RX + TX signals from the device on J2 are converted and linked to the MIDI IN and MIDI OUT 5 pin DIN sockets.

This allows any Nextion HMI running an appropriate firmware and communicating at the standardized MIDI baud rate (31250 baud) to act as an autonomous (without external MCU) MIDI sender, receiver, and controller! While this interface has worldwide standardized MIDI IN and MIDI OUT sockets, MIDI THRU can be implemented as soft-THRU in firmware/software by the device connected to J2. Use without Nextion HMI: As an extra feature, the Nextion MIDI I/O interface can also serve without a Nextion HMI: Simply connect a MCU (Arduino, Teensy, PIC, STM, Raspberry PI, and more) running MIDI software to J2. Think of linking the MCU‘s TX with the interface‘s RX and vice-versa. In such a setup, the on-board switch SW1 allows to reprogram your MCU via serial from any source connected to J1 when set to PRGM mode. Specifications: Model name: Nextion MIDI I/O interface Operation voltage: 5V Current consumption: max 13mA Pass-through current for 5V power supply from J1 to J2: 2A max TTL RX level in MIDI mode: 3.3V, 5V tolerant TTL TX level in MIDI mode: 5V For use with 3.3V MCUs in an alternative setup without Nextion HMI, please use a level converter or contact our technical support MIDI loop current: ~5mA, EMI filtered MIDI connectors: 2 x standardized 5 pin DIN TTL serial and power supply connectors: 2 x 4 pin XH 2.5mm Working temperature: -20°C ~ 70°C PCB size: 67mm x 38mm x 25mm Nextion compatibility: All series, Basic, Discovery, Enhanced, and Intelligent In the box: Nextion MIDI I/O Interface x 1 XH2.54 4P wire x 2 Additional information: The Nextion MIDI I/O Interface was developed in cooperation with the French electronic music expert Thierry Frenkel, and his dVox::Instruments brand. Video Manual: Links to Nextion+Midi programming resources:

• Protocols and parsing – Part 2: MIDI – the basics
• Protocols and parsing – Part 3: Sending MIDI messages from Nextion HMI
• Protocols and parsing – Part 4: Receiving and decoding MIDI messages

More articles and videos:

• The Nextion MIDI I/O interface – The first video
• Show and tell – A polyphonic MIDI keyboard on screen demo