Question

Android 手机上的 USB MIDI 是做什么用的?怎么用?

Answer 1

USB test: peripheral mode(这种模式下USB从设备是作为一个MIDI键盘！！)

Hardware needed: USB cable, OTG adapter
Android-to-Android
Apps needed: MidiKeyboard on Android device under test, MidiScope on another Android device.
Use Android devices as a peripheral controller for another Android device. To help test this mode, use another Android device running in host mode. Note that you could modify the test to work with a desktop computer running Digital Audio Workstation (DAW) software such as GarageBand.
Connect the USB cable to the Android device under test (Android device A).
Use an OTG adapter to connect the other end of the cable to a second Android device B that operates in host mode.
On Android device A:
Drag finger down from top of screen.
Select USB for Charging icon.
Select MIDI.
Launch MidiKeyboard app.
Select Android USB Peripheral Port from Receiver for Keys menu at top.
On Android device B:
Launch MidiScope app.
Select the other Android device as the source.
On Android device A:
Play notes on the keyboard and look for NoteOn and NoteOff on Android device B.

另外文章里还介绍了 MIDI 可以走 USB Host Mode/USB Peripheral Mode/BLE, 以及相应的测试方法.

Answer 2

USB Type-C接口是一个新的USB接口，跟老的USB接口不兼容（不过可以通过转接头来使用老的USB 3.0或2.0设备），其最大的优势在于支持双向插拔（不必担心第一次就插反了），还有双向充电（你的平板可以给手机供电了）。

当你将USB Type-C插头插入到Android手机之后，会看到下面的提示，你可以选择充电、为其它设备供电、传输文件、传输照片或是传输MIDI：

不过MIDI的传输只是单向的，只能将手机或平板作为MIDI输入设备使用，也就是说其它设备可以传输MIDI信息到手机里，而暂时不能让手机发出MIDI信息。也就是Android M可以作为音源，连接你的外部MIDI键盘来演奏。