nRF5340Dk configuration for Unicast Audio server with External I2S CODEC

Question

Hi,
I am using nRF5340 for my unicast Audio server example where the nRF5340DK is the headset and my mobile device is the audio source. I have taken the unicast audio server example from the Zephyr. Since this DK do not have a I2S Decoder I am using an external I2S DAC (CJMCU-1334 UDA1334A I2S DAC Audio Stereo Decoder Module) . I have added overlay file for configuring the I2S peripheral as follows. I am using SDK 2.7.0

&pinctrl {
    i2s0_default: i2s0_default {
        group1 {
            psels = <NRF_PSEL(I2S_SCK_M, 0, 15)>,
                   <NRF_PSEL(I2S_LRCK_M, 0, 12)>,
                   <NRF_PSEL(I2S_SDOUT, 0, 13)>,
                   <NRF_PSEL(I2S_SDIN, 0, 14)>;
        };
    };
};
&clock {
	hfclkaudio-frequency = <11289600>;
};

&i2s0 {
    status = "okay";
    pinctrl-0 = <&i2s0_default>;
    pinctrl-names = "default";
};

I have also made some changes in the main.c and also for initializing the I2S. The changed portions are also attaching .

#if defined(CONFIG_LIBLC3)

static void stream_recv_lc3_codec(struct bt_bap_stream *stream,
				  const struct bt_iso_recv_info *info,
				  struct net_buf *buf)
{
	const uint8_t *in_buf;
	uint8_t err = -1;
	const int octets_per_frame = buf->len / frames_per_sdu;
	void *tx_block;
	size_t tx_size;

	if (lc3_decoder == NULL) {
		printk("LC3 decoder not setup, cannot decode data.\n");
		return;
	}

	if ((info->flags & BT_ISO_FLAGS_VALID) == 0) {
		printk("Bad packet: 0x%02X\n", info->flags);

		in_buf = NULL;
	} else {
		in_buf = buf->data;
	}

	/* This code is to demonstrate the use of the LC3 codec. On an actual implementation
	 * it might be required to offload the processing to another task to avoid blocking the
	 * BT stack.
	 */
	for (int i = 0; i < frames_per_sdu; i++) {

		int offset = 0;

		err = lc3_decode(lc3_decoder, in_buf + offset, octets_per_frame,
				 LC3_PCM_FORMAT_S16, audio_buf, 1);

		if (in_buf != NULL) {
			offset += octets_per_frame;
		}
	}

	printk("RX stream %p len %u\n", stream, buf->len);

	if (err == 1) {
		printk("  decoder performed PLC\n");
		return;

	} else if (err < 0) {
		printk("  decoder failed - wrong parameters?\n");
		return;
	}

	if (!i2s_configured) {
        printk("Warning: I2S not configured, skipping audio output\n");
        return;
    }

	/* Write decoded audio data to I2S */
    err = i2s_buf_read(i2s_dev, &tx_block, &tx_size);
    if (err < 0) {
        printk("Failed to get I2S TX buffer: %d\n", err);
        return;
    }

    /* Copy decoded audio data to TX block */
    memcpy(tx_block, audio_buf, MIN(tx_size, sizeof(audio_buf)));

    /* Send the audio data */
    err = i2s_buf_write(i2s_dev, tx_block, MIN(tx_size, sizeof(audio_buf)));
    if (err < 0) {
        printk("Failed to write I2S TX buffer: %d\n", err);
        return;
    }
}

#include <zephyr/device.h>
#include <zephyr/drivers/i2s.h>
#include <zephyr/drivers/gpio.h>
#include <nrf.h>

/* Add these global variables for I2S */
static const struct device *i2s_dev;
#define NUM_SAMPLES 32
#define NUM_BLOCKS 8
static bool i2s_configured = false;
K_MEM_SLAB_DEFINE(i2s_tx_mem_slab, BT_ISO_SDU_BUF_SIZE(CONFIG_BT_ISO_TX_MTU) * 2, NUM_BLOCKS, NUM_SAMPLES);

static int init_i2s(void)
{
    /* Configure I2S */
    struct i2s_config i2s_cfg;
    int ret;

    /* Get I2S device */
    i2s_dev = DEVICE_DT_GET(DT_NODELABEL(i2s0));
    if (!device_is_ready(i2s_dev)) {
        printk("I2S device not ready\n");
        return -ENODEV;
    }

    /* Configure I2S TX */
    i2s_cfg.word_size = 16;
    i2s_cfg.channels = 2;
    i2s_cfg.format = I2S_FMT_DATA_FORMAT_I2S;
    i2s_cfg.options = I2S_OPT_FRAME_CLK_MASTER | I2S_OPT_BIT_CLK_MASTER;
    i2s_cfg.frame_clk_freq = 48000;
    i2s_cfg.block_size = BT_ISO_SDU_BUF_SIZE(CONFIG_BT_ISO_TX_MTU);
    i2s_cfg.mem_slab = &i2s_tx_mem_slab;
    i2s_cfg.timeout = 0;
	
    ret = i2s_configure(i2s_dev, I2S_DIR_TX, &i2s_cfg);
    if (ret < 0) {
        printk("Failed to configure I2S TX: %d\n", ret);
        return ret;
    }

    /* Start I2S TX */
    ret = i2s_trigger(i2s_dev, I2S_DIR_TX, I2S_TRIGGER_START);
    if (ret < 0) {
        printk("Failed to start I2S TX: %d\n", ret);
        return ret;
    }

	i2s_configured = true;  // Set flag indicating I2S is configured

    printk("I2S initialized successfully\n");
    return 0;
}

with these changes I am able to build and flash the code to the nRF5340 Dk. I am able to connect with the mobile device with the DK as a audio device, but i have faced some errors at the starting. The errors are also attached.

Ignoring the first error I connected the device and when I played audio in the source , the error in the below screenshot happened causing the system halt.

I understand the errors happened due to some memory buffer issues. But couldn't able to point out the exact point.