Hi, I am new to this forum so let mw know if there is a better place for this type of question regarding MIDI applications on openwrt.
Let's start with my current setup: An electronic piano transmitting MIDI through a USB host interface to a windoze laptop running rtpmidi. This computer is wired to my GL-Ar750s router running "pure" openwrt 23.05.2. The router hosts a dedicated WIFI for an iphone that is receiving the MIDI signal and generating the sound. The performance is surprisingly good with latency around 3-4ms.
Since my router has a USB port and there is a "rtpmidid" package available. I would like to bypass the windows laptop completely and just use the router to connect everything but I do not know if it is possible or where to start. I have a Yamaha p-105 piano BTW.
Can't help you with any direct experience, but it appears that there are indeed some midi packages available, including rtpmidid:
gst1-mod-midi - 1.20.5-1 - GStreamer open source multimedia framework . This package contains the GStreamer midi support plugin.
midisport-firmware - 1.2-1 - This package allows you to use the MidiSport USB MIDI interfaces from M-Audio/Midiman. Supported devices: - MidiSport 1x1 - MidiSport 2x2 - MidiSport 4x4 - MidiSport 8x8 - MidiSport Uno - Keystation - Oxygen - Radium (You don't need a firmware download for the USB Audio Quattro, Duo, or MidiSport 2x4.)
rtpmidid - 2022-07-07-eab5cd80-1 - rtpmidid is an user daemon, and when a RTP MIDI device is announced using mDNS (also known as Zeroconf, Avahi, and multicast DNS) it exposes this ALSA sequencer port.
ttymidi-sysex - 2021-05-07-e519a116-3 - ttymidi is a GPL-licensed program that allows external serial devices to interface with ALSA MIDI applications. The main motivation behind ttymidi was to make Arduino boards talk to MIDI applications without the need to use (or build) any extra hardware.
That said, the other option would be to get a USB adapter for your phone and just plug your USB keyboard connection directly into the phone. This probably should work with the same application you're using. If your iPhone is lighting, you'd get the Lightning to USB3 Camera Adapter. If you're using an iPhone 15 with USB-C, a USB-C to USB-A cable should do the trick.
Indeed there are a few MIDI packages out there but they seems to be very context specific. That said, the other option, the OTG adapter/usb hub, is of course the mainstream solution but It would not be as much fun as trying to reuse existing (and cool) hardware! 