samples: drivers: i2s: Support sine wave playback in i2s_codec sample

- when not using DMIC, play a 16kHz stereo sine wave using codec

Signed-off-by: Tomas Barak <tomas.barak@nxp.com>

Author: TomasBarakNXP

samples/drivers/i2s/i2s_codec/README.rst

@@ -8,7 +8,7 @@ Overview
 ********
 
 This sample demonstrates how to use an I2S driver in a simple processing of
-an audio stream. It configures and starts from memory buffer or from DMIC to
+an audio stream. It configures and starts from memory buffer (sample sine wave) or from DMIC to
 record i2s data and send to codec with DMA.
 
 Requirements
@@ -30,4 +30,4 @@ To build and flash the application:
    :compact:
 
 To run you can connect earphones to the lineout connect and hear the sound
-from DMIC or from memory buffer.
+from DMIC or from memory buffer. Sample sine wave is included for reference.

samples/drivers/i2s/i2s_codec/src/main.c

@@ -1,5 +1,5 @@
 /*
- * Copyright 2024 NXP
+ * Copyright 2024-2025 NXP
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -11,6 +11,9 @@
 #include <zephyr/audio/codec.h>
 #include <string.h>
 
+#ifndef CONFIG_USE_DMIC
+#include "sine.h"
+#endif
 
 #define I2S_CODEC_TX  DT_ALIAS(i2s_codec_tx)
 
@@ -171,19 +174,14 @@ int main(void)
 
 			for (i = 0; i < 2; i++) {
 #if CONFIG_USE_DMIC
-				ret = dmic_read(dmic_dev, 0,
-								&mem_block, &block_size, TIMEOUT);
+				ret = dmic_read(dmic_dev, 0, &mem_block, &block_size, TIMEOUT);
 				if (ret < 0) {
 					printk("read failed: %d", ret);
 					break;
 				}
 #else
-				ret = k_mem_slab_alloc(&mem_slab,
-							&mem_block, Z_TIMEOUT_TICKS(TIMEOUT));
-				if (ret < 0) {
-					printk("Failed to allocate TX block\n");
-					return 0;
-				}
+				/* If not using DMIC, play a sine wave 440Hz */
+				mem_block = (void *)&__16kHz16bit_stereo_sine_pcm;
 #endif
 				ret = i2s_write(i2s_dev_codec, mem_block, block_size);
 				if (ret < 0) {