| page.title=MIDI |
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| |
| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol id="auto-toc"> |
| </ol> |
| </div> |
| </div> |
| |
| <p> |
| <a href="http://en.wikipedia.org/wiki/MIDI">MIDI</a> (Musical Instrument Digital Interface) |
| is a standard protocol for inter-connecting computers with musical instruments, stage lighting, |
| and other time-oriented media. |
| </p> |
| |
| <p> |
| The physical <a href="http://en.wikipedia.org/wiki/Transport_layer">transport layer</a> |
| specified in original MIDI 1.0 is a current loop with |
| <a href="http://en.wikipedia.org/wiki/DIN_connector">5-pin DIN</a> connector. |
| </p> |
| |
| <p> |
| Since MIDI 1.0, additional transports have been defined, including MIDI over USB |
| and a proposed draft for MIDI over |
| <a href="http://en.wikipedia.org/wiki/Bluetooth_low_energy">Bluetooth Low Energy</a> (BLE.) |
| </p> |
| |
| <p> |
| Strictly speaking, MIDI is unrelated to audio. But since MIDI is commonly used with |
| music, this article is placed in the audio section. |
| </p> |
| |
| <h2>MIDI for Android</h2> |
| |
| <p> |
| Android 3.1 and later support |
| <a href="http://en.wikipedia.org/wiki/USB_On-The-Go">USB On-The-Go</a>, |
| which permits an Android device to act as USB host to drive USB |
| peripherals. The USB host mode APIs introduced in Android 3.1 permit |
| developers to implement MIDI over USB at the application level, but until |
| recently there have been no built-in platform APIs for MIDI. |
| </p> |
| |
| <p> |
| Beginning with the Android M release, device makers can enable optional MIDI support in the platform. |
| Supported transports include USB, draft BLE, and virtual (inter-app). |
| </p> |
| |
| <p> |
| For details on application programming with the new MIDI APIs, |
| first download the |
| <a href="https://developer.android.com/preview/download.html#docs">preview reference</a> |
| and then see the <code>android.media.midi</code> package. |
| </p> |
| |
| <p> |
| The remainder of this article discusses how an Android device maker can |
| enable MIDI support in the platform. |
| </p> |
| |
| <h2>Enabling transports</h2> |
| |
| <h3>USB host mode</h3> |
| |
| <p> |
| To enable MIDI for USB host mode, first support USB host mode in general, and |
| then enable <code>CONFIG_SND_RAWMIDI</code> in your kernel configuration. |
| </p> |
| |
| <h3>USB peripheral mode</h3> |
| |
| <p> |
| To enable MIDI for USB peripheral mode, you may need to apply patches |
| to your Linux kernel to integrate the |
| <code>drivers/usb/gadget/f_midi.c</code> into the USB gadget |
| driver. As of this writing, these patches are available for Linux kernel version |
| 3.10. These patches have not yet been updated for |
| <a href="http://en.wikipedia.org/wiki/Configfs">ConfigFs</a> |
| (a new architecture |
| for USB gadget drivers), nor are they merged at upstream |
| <a href="http://kernel.org"</a>kernel.org</a>. |
| </p> |
| |
| <p> |
| The patches are shown in commit order for the <code>tegra</code> tree: |
| </p> |
| <ol> |
| <li><a href="https://android.googlesource.com/kernel/tegra/+/261230ce54cfc119efe643fc1d128e431d1678d3"</a>261230ce54cfc119efe643fc1d128e431d1678d3</a></li> |
| <li><a href="https://android.googlesource.com/kernel/tegra/+/3f048135f3028e503d9d6e32b602e362bd9f374f"</a>3f048135f3028e503d9d6e32b602e362bd9f374f</a></li> |
| <li><a href="https://android.googlesource.com/kernel/tegra/+/ae2019d83ecf14454315240c16dc3136212f0da2"</a>ae2019d83ecf14454315240c16dc3136212f0da2</a></li> |
| </ol> |
| |
| <p> |
| In addition, the end user must also check the box for MIDI |
| in the <em>Settings</em> dialog for <em>Select USB configuration</em>, |
| or by pulling down from the top of screen while attached |
| to the USB host, and choosing <strong>MIDI</strong> for "Use USB for ...". |
| </p> |
| |
| <h3>BLE</h3> |
| |
| <p> |
| MIDI over BLE is always enabled. |
| As this transport is in draft status, it is subject to change. |
| </p> |
| |
| <h3>Virtual (inter-app)</h3> |
| |
| <p> |
| The virtual (inter-app) transport is always enabled. |
| </p> |
| |
| <h2>Claiming the feature</h2> |
| |
| <p> |
| Applications can screen for the presence of MIDI support using the |
| <code>android.software.midi</code> feature. |
| </p> |
| |
| <p> |
| To claim MIDI support, add this line to your <code>device.mk</code>: |
| </p> |
| <pre> |
| PRODUCT_COPY_FILES += \ |
| frameworks/native/data/etc/android.software.midi.xml:system/etc/permissions/android.software.midi.xml |
| </pre> |
| |
| <p> |
| See the |
| <a href="{@docRoot}compatibility/android-cdd.pdf">Android Compatibility Definition Document (CDD)</a> |
| for information |
| on requirements to claim the feature. |
| </p> |
| |
| <h2 id="hostDebugging">Debugging while in host mode</h2> |
| |
| <p> |
| While in USB host mode, Android Debug Bridge (adb) debugging over USB is unavailable. |
| See section <a href="http://developer.android.com/tools/help/adb.html#wireless">Wireless usage</a> |
| of |
| <a href="http://developer.android.com/tools/help/adb.html">Android Debug Bridge</a> |
| for an alternative. |
| </p> |