Add basic sample rate conversion to the CXD56 Spresense audio
driver using libsamplerate. Currently conversion is only done
during playback and all output is fixed at 48 kHz.
Issues:
- 16 kHz SRC has glitches (unless data dump is enabled)
- 44.1 kHz SRC gets stuck
Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
Adds an initial Nuttx audio driver supporting the Spresense CXD56.
Being a work in progress the driver has a number of limitations:
- Audio playback only, no recording yet.
- Only 16 bit stereo playback is supported.
- In practice only 48kHz playback is supported due to missing SRC.
- Configure driver in "Device Drivers --> Audio Device Support".
This commit does two things:
1. First, it reorganizes the driver Kconfig files so that each is self contained. Before, a part of the driver configuration was in drivers/Kconfig and the rest was in in drivers/xyz/Konfig. Now, all of the driver configuration is consolitated in the latter.
2. Second, this commit correct numerous serious errors introduced in a previous reorganization of the driver Kconfig files. This was first noted by Nicholas Chin in PR270 for the case of the drivers/i2c/Kconfig but some examination indicates that the error was introduced into several other Kconfig files as well.
The nature of the introduced error was basically this:
- Nothing must intervene between the menuconfig selection and the following conditional configuration otpions.
- A previous PR erroneously introduced unconditional options between the menuconfig and the following confditional logic, thus corrupting the driver menus.
This error was easy to make because the driver Kconfig files were not well modularized. Making them fully self-contained should eliminate this kind of error in the future.
