--- title: "ESP32_Host_MIDI" url: "https://maker.wiznet.io/lawrence/projects/esp32-host-midi/" markdown_url: "https://maker.wiznet.io/lawrence/projects/esp32-host-midi/md" type: "UCC: User Created Content" author: "Saulo Verissimo" author_url: "https://github.com/sauloverissimo/ESP32_Host_MIDI" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "Saulo Verissimo" original_url: "https://github.com/sauloverissimo/ESP32_Host_MIDI" published: "2026-02-26" language: "en" tags: ["MIDI", "ESP32", "W5500", "ApplieMIDI", "RTR-MIDI"] hardware: ["Espressif ESP32", "WIZnet W5500"] likes: 0 views: 544 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # ESP32_Host_MIDI > ESP32_Host_MIDI Original author: Saulo Verissimo (source: https://github.com/sauloverissimo/ESP32_Host_MIDI) ## Components - **Espressif ESP32** x 1 ([docs](https://www.espressif.com/en/products/socs/esp32)) - **WIZnet W5500** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500)) WIZnet parts: W5500 ([Datasheet](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/datasheet?utm_source=maker&utm_medium=project&utm_campaign=w5500), [product hub](https://maker.wiznet.io/products/w5500/)) ## Article ## ESP32 + W5500 Wired Ethernet MIDI Hub: Overview of the ESP32_Host_MIDI Project (AppleMIDI / RTP-MIDI) This article presents **ESP32_Host_MIDI**, an open-source library that enables an ESP32 to operate as a **general-purpose, multi-transport MIDI hub**. The library consolidates multiple MIDI transports—**USB Host, BLE MIDI, Wi-Fi RTP-MIDI, OSC, DIN-5 (UART), ESP-NOW, USB Device, and MIDI 2.0 / UMP over UDP**—under a **unified programming interface**, supporting rapid development of MIDI **routers, bridges, and controllers** for a wide range of system architectures. --- ### Project Objectives and Use Cases Modern MIDI environments frequently require interoperability across heterogeneous interfaces and protocols. Typical requirements include: Connecting a **USB MIDI keyboard** to a DAW via **wired or wireless networking** Bridging **BLE MIDI** applications on iPad/iPhone with studio equipment (e.g., DIN-5 synthesizers and DAWs) Centralizing MIDI routing in setups that combine multiple devices and transports ESP32_Host_MIDI addresses these requirements by abstracting transport-specific behavior and enabling the ESP32 to function as a **central routing and translation node**, supporting flexible integration for instruments, software tools, and interactive installations. --- ### Representative Application Scenarios The library can be applied to the following system-level scenarios: **Studio rack bridge**: DIN-5 (legacy) synthesizer → ESP32 → DAW via **Ethernet MIDILive / rehearsal systems**: multiple ESP32 nodes connected through ESP-NOW, with MIDI forwarded to FOH via USB or network transport **Custom MIDI controllers**: sensor/knob/fader inputs mapped to MIDI Notes/CC and transmitted via USB, BLE, or network **Media art and software integration**: OSC ↔ MIDI bridging for environments such as Max/MSP or TouchOSC --- ### System Overview A common deployment model aggregates MIDI input sources (USB/BLE/DIN-5) at the ESP32 and forwards MIDI as **network MIDI (AppleMIDI / RTP-MIDI)** over **wired Ethernet** using the W5500. ```c [USB MIDI Keyboard] [BLE MIDI (iPhone/iPad)] [DIN-5 Synth] \ | / \ | / -----> [ESP32_Host_MIDI] ----- (routing / filtering / bridging) | SPI | v [W5500] | Ethernet | [Mac / DAW] (Audio MIDI Setup - Network MIDI) ``` ### Ethernet Implementation and Rationale for W5500 The project includes a **wired Ethernet MIDI** configuration (“Ethernet-MIDI”). In this approach, the ESP32 interfaces with a **W5500 SPI Ethernet module** and runs **AppleMIDI (RTP-MIDI)** over wired Ethernet. **Implementation summaryHardware**: ESP32 + W5500 (SPI) module + RJ-45 **Software**: Arduino Ethernet library + lathoub’s Arduino-AppleMIDI-Library (v3.x) **Ports**: typically a **consecutive UDP port pair**, such as **5004 / 5005** (implementation-dependent and configurable) **Rationale for W5500Hardwired TCP/IP with integrated MAC/PHY**: W5500 integrates key network functions, allowing the MCU to remain focused on time-critical processing (e.g., MIDI handling, USB processing, input scanning) while maintaining a straightforward Ethernet interface. **Deterministic behavior on wired Ethernet**: For timing-sensitive MIDI workloads, wired Ethernet often provides more stable latency and jitter characteristics than Wi-Fi in studio and installation environments, which can improve timing consistency. --- ## Protocol Overview: AppleMIDI vs RTP-MIDI (Including Stack and Port Model) Although the terms are often used together, **AppleMIDI** and **RTP-MIDI** represent different functional layers. ### 1) AppleMIDI vs RTP-MIDI **RTP-MIDI** specifies how MIDI messages are encapsulated within **RTP packets**—i.e., the **payload format** used to transport Note/CC/etc. over RTP/UDP. **AppleMIDI** provides the **session management and synchronization framework** used by macOS/iOS Network MIDI, including session invitation/acceptance, connection lifecycle control, clock synchronization, and feedback mechanisms required for stable real-time operation. In practical terms: **RTP-MIDI** defines the **data representation** on the wire. **AppleMIDI** defines the **session and synchronization behavior** required to operate that stream reliably. ### 2) Protocol Stack (Layer View) A typical network MIDI data path can be described as: **MIDI messages** → **RTP-MIDI payload** → **RTP** → **UDP** → **IP** → **Ethernet (wired, via W5500)** In this model, W5500 provides the Ethernet/IP/UDP foundation, while AppleMIDI and RTP-MIDI operate at higher layers. --- ### 3) Two-Port Model (Control / Data) AppleMIDI commonly uses **two consecutive UDP ports (N and N+1)**: **Control Port (e.g., 5004)** Handles session control traffic such as invitation/accept/deny, session teardown, and related feedback/control messages. **Data Port (e.g., 5005)** Carries the RTP-MIDI stream (Notes, CC, etc.), and timing-related exchanges are also performed on the data side. This separation improves operational clarity and helps maintain stability for time-critical streaming by isolating session control traffic from the data stream. **Operational note**: In NAT/firewall environments, the **port pair** must be considered as a unit; opening or forwarding only one port is typically insufficient. ## Q&A (Answer Engine Optimization) ### Q1. What is ESP32_Host_MIDI? **ESP32_Host_MIDI is an open-source library that turns an ESP32 into a multi-transport MIDI hub.** It unifies USB Host, BLE MIDI, Wi-Fi RTP-MIDI, OSC, DIN-5 (UART), ESP-NOW, USB Device, and MIDI 2.0/UMP over UDP behind a single API. ### Q2. What can you build with ESP32_Host_MIDI? **You can build MIDI routers, bridges, and custom controllers that connect multiple MIDI interfaces in one device.** Typical builds include studio Ethernet MIDI bridges, live rig routing nodes, sensor-based controllers, and OSC↔MIDI gateways. ### Q3. What is RTP-MIDI? **RTP-MIDI is a method for carrying MIDI messages inside RTP packets over UDP/IP networks.** It defines how Note/CC and other MIDI events are packed and transmitted on a network link. ### Q4. What is AppleMIDI? **AppleMIDI is the session and synchronization layer used by macOS/iOS Network MIDI for RTP-MIDI streams.** It manages session invitation/accept/teardown, clock synchronization, and feedback so the RTP-MIDI stream operates reliably in real time. ### Q5. What is the difference between AppleMIDI and RTP-MIDI? **RTP-MIDI defines the data format, while AppleMIDI defines the session and synchronization behavior.** In practice, RTP-MIDI describes how MIDI is packaged, and AppleMIDI describes how devices connect, maintain timing, and manage the stream. --- Source: https://maker.wiznet.io/lawrence/projects/esp32-host-midi/