zephyr

History

Keith Packard 0b90fd5adf samples, tests, boards: Switch main return type from void to int As both C and C++ standards require applications running under an OS to return 'int', adapt that for Zephyr to align with those standard. This also eliminates errors when building with clang when not using -ffreestanding, and reduces the need for compiler flags to silence warnings for both clang and gcc. Most of these changes were automated using coccinelle with the following script: @@ @@ - void + int main(...) { ... - return; + return 0; ... } Approximately 40 files had to be edited by hand as coccinelle was unable to fix them. Signed-off-by: Keith Packard <keithp@keithp.com>		2023-04-14 07:49:41 +09:00
..
boards	samples: Remove label property from devicetree overlays	2022-08-01 17:59:32 +02:00
dts/bindings	samples: drivers: Add I2S echo sample	2021-07-28 18:41:26 -04:00
src	samples, tests, boards: Switch main return type from void to int	2023-04-14 07:49:41 +09:00
CMakeLists.txt	cmake: increase minimal required version to 3.20.0	2021-08-20 09:47:34 +02:00
Kconfig	samples: i2s: echo: Remove DT_COMPAT_<compat> defines	2022-09-01 14:58:25 +00:00
prj.conf	samples: drivers: Add I2S echo sample	2021-07-28 18:41:26 -04:00
README.rst	samples: drivers: Add I2S echo sample	2021-07-28 18:41:26 -04:00
sample.yaml	samples: Replace i2s tag with lower case	2023-01-10 18:29:35 -05:00

README.rst

.. _i2s_echo_sample:

I2S Echo Sample
###############

Overview
********

This sample demonstrates how to use an I2S driver in a simple processing of
an audio stream. It configures and starts both the RX and TX streams and then
mixes the original signal with its delayed form that is buffered, providing
a simple echo effect.

Requirements
************

The sample uses the WM8731 audio CODEC that can be found, for example,
on the Audio Codec Shield, but it can be easily adapted to use other
CODECs. The I2S device to be used by the sample is specified by defining
a devicetree node label named ``i2s_rxtx`` or separate node labels ``i2s_rx``
and ``i2s_tx`` if separate I2S devices are to be used for the RX and TX
streams.

This sample has been tested on :ref:`nrf52840dk_nrf52840` (nrf52840dk_nrf52840)
and :ref:`nrf5340dk_nrf5340` (nrf5340dk_nrf5340_cpuapp), using the Audio Codec
Shield, and provides overlay files for both of these boards.

More information about the used shield and the CODEC itself can be found here:

- `Audio Codec Shield`_
- `WM8731`_

Building and Running
********************

The code can be found in :zephyr_file:`samples/drivers/i2s/echo`.

To build and flash the application:

.. zephyr-app-commands::
   :zephyr-app: samples/drivers/i2s/echo
   :board: nrf52840dk_nrf52840
   :goals: build flash
   :compact:

Press Button 1 to toggle the echo effect and Button 2 to stop the streams.

.. _Audio Codec Shield: http://wiki.openmusiclabs.com/wiki/AudioCodecShield
.. _WM8731: https://www.cirrus.com/products/wm8731/