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AN00248 doc updates

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xross
2018-04-04 18:17:18 +01:00
parent a3c7ff3dd5
commit aaf3944d18
1 changed files with 8 additions and 6 deletions
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examples/AN00248_xua_example_pdm_mics/doc/rst/AN00248.rst
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@@ -8,7 +8,7 @@ Overview
Introduction
............
The XMOS USB Audio (XUA) library provides an implemention of USB Audio Class versions 1.0 and 2.0.
The XMOS USB Audio (XUA) library provides an implementation of USB Audio Class versions 1.0 and 2.0.
This application note demonstrates the implementation of a basic USB Audio Device with
record functionality from PDM microphones on the xCORE-200 Array Microphone board.
@@ -75,7 +75,7 @@ Declarations
Allocating hardware resources for lib_xua
.........................................
A minimal implementation of a USB Audio device using ``lib_xua``, without I2S functionalilty,
A minimal implementation of a USB Audio device using ``lib_xua``, without I2S functionality,
requires the follow I/O pins:
- Audio Master clock (from clock source to xCORE)
@@ -139,7 +139,7 @@ Other declarations
For a simple application the following endpoints are required:
- ``Control`` enpoint zero
- ``Control`` endpoint zero
- ``Isochonous`` endpoint for each direction for audio data to/from the USB host
These are declared as follows:
@@ -175,7 +175,7 @@ complete contents of this file are as follows:
The application main() function
-------------------------------
The ``main()`` function sets up the tasks in the application.
The ``main()`` function sets up and runs the tasks in the application.
Channel declarations
....................
@@ -214,11 +214,13 @@ Microphone related tasks are executed on tile 0 as follows:
:start-on: Microphone related tasks
:end-before: return 0
Two functions from ``lib_mic_array`` are used - a PDM receiver task (``mic_array_pdm_rx()``) and a decimation task (``mic_array_decimate_to_pcm_4ch()``).
Each call to ``mic_array_decimate_to_pcm_4ch()`` can handle the decimation of up to 4 microphone signals. Since the xCORE-200 Array microphone
board is equipped with seven microphones two instances of this task are run.
The ``mic_array_pdm_rx()`` task expects the PDM microphone port to be clocked from the PDM clock.
Note that the ``spdif_tx_port_config()`` function is called before a nested ``par`` of ``spdif_tx()`` and ``XUA_AudioHub()``.
This is because of the "shared" nature of ``p_mclk_in`` and avoids a parrallel usage check failure by the XMOS toolchain.
|appendix|
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