forked from PAWPAW-Mirror/lib_xua
48 lines
2.5 KiB
ReStructuredText
Executable File
48 lines
2.5 KiB
ReStructuredText
Executable File
Audio Controls via Human Interface Device (HID)
|
|
===============================================
|
|
|
|
The design supports simple audio controls such as play/pause, volume up/down etc via the USB Human
|
|
Interface Device Class Specification.
|
|
|
|
This functionality is enabled by setting the ``HID_CONTROLS`` define to ``1``. Setting to ``0``
|
|
disables this feature.
|
|
|
|
When turned on the following items are enabled:
|
|
|
|
#. HID descriptors are enabled in the Configuration Descriptor informing the host that the device has HID interface
|
|
#. A Get Report Descriptor request is enabled in ``endpoint0``.
|
|
#. Endpoint data handling is enabled in the ``buffer`` core
|
|
|
|
The Get Descriptor Request enabled in endpoint 0 returns the report descriptor for the HID device.
|
|
This details the format of the HID reports returned from the device to the host. It maps a bit in
|
|
the report to a function such as play/pause.
|
|
|
|
The USB Audio Framework implements a report descriptor that should fit most basic audio device controls.
|
|
If further controls are necessary the HID Report Descriptor in ``descriptors.h`` should be modified.
|
|
The default report size is 1 byte with the format as follows:
|
|
|
|
.. table:: Default HID Report Format
|
|
|
|
+-------------+-------------------------+
|
|
| Bit | Function |
|
|
+=============+=========================+
|
|
| 0 | Play/Pause |
|
|
+-------------+-------------------------+
|
|
| 1 | Scan Next Track |
|
|
+-------------+-------------------------+
|
|
| 2 | Scan Prev Track |
|
|
+-------------+-------------------------+
|
|
| 3 | Volume Up |
|
|
+-------------+-------------------------+
|
|
| 4 | Volume Down |
|
|
+-------------+-------------------------+
|
|
| 5 | Mute |
|
|
+-------------+-------------------------+
|
|
| 6-7 | Unused |
|
|
+-------------+-------------------------+
|
|
|
|
On each HID report request from the host the function ``Vendor_ReadHidButtons(unsigned char hidData[])`` is called from ``buffer()``. This function is passed an array ``hidData[]`` by reference. The programmer should report the state of his buttons into this array. For example, if a volume up command is desired, bit 3 should be set to 1, else 0.
|
|
|
|
Since the ``Vendor_ReadHidButtons()`` function is called from the ``buffer`` logical core, care should be taken not to add to much execution time to this function since this could cause issues with servicing other endpoints.
|
|
|