SPH0645 I2S MIC DATA FORMAT

[Kashyap23]

Hi,I have been using nrf5340 audio DK Board to access the I2S .I am using SPH0645 mic with that i need to get mic data .My Mic datasheet specifies that "The Data Format is I2S, 24-bit, 2’s compliment, MSB first. The data precision is 18 bits; unused bits are zeros".Do I need to convert the value ? As it specifies data of 2's complement value in order to get original mic data or it will be internally converted by the nrf5340 controller itself.I am taking data size of 32 bit and in that I am taking 16 bit of each mic data and confirm me regarding data format whether to be Left-justified or Right-justified.I am attaching the Datasheet of I2s mic.

Regards,

Kashyap

[Kashyap23]

Kashyap23 said:

data of 2's complement value in order to get original mic data or it will be internally converted by the nrf5340 controller

Ok,thank's for that .I have doubt regard data ,I am trying to print data and convert to wav file,in this case do i need any conversion of 2's complement value to get original audio or this wont be necessary thing.Can I use directly what I get without converting 2's complement value?

[Elfving]

Kashyap23 said:

Can I use directly what I get without converting 2's complement value?

That should be fine, 2's complement is normal. 

Regards,

Elfving

[Kashyap23]

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&pinctrl {
i2s0_default: i2s0_default {
group1 {
psels = <NRF_PSEL(I2S_SCK_M, 0, 26)>,
<NRF_PSEL(I2S_LRCK_M, 0, 25)>,
<NRF_PSEL(I2S_SDIN, 0, 7)>,
<NRF_PSEL(I2S_SDOUT, 0, 6)>;
};
};
i2s0_sleep: i2s0_sleep {
group1 {
psels = <NRF_PSEL(I2S_SCK_M, 0, 26)>,
<NRF_PSEL(I2S_LRCK_M, 0, 25)>,
<NRF_PSEL(I2S_SDIN, 0, 7)>,
<NRF_PSEL(I2S_SDOUT, 0, 6)>;
};
};
};

&clock {
status = "okay";
hfclkaudio-frequency = <12288000>;
};


i2s_rxtx: &i2s0 {
status = "okay";
pinctrl-0 = <&i2s0_default>;
pinctrl-1 = <&i2s0_sleep>;
clock-source = "ACLK";
pinctrl-names = "default","sleep";
};

 Ok,In that case help me with getting data as I am not able to get mic data correctly.Here I am just reading and logging manually and using that i iam converting to wav file externally to check audio.But using this I am not getting all data,some data is not printing and dont know it is correct data or not

#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>
#include <zephyr/drivers/i2s.h>
#include <zephyr/drivers/gpio.h>
#include <string.h>
#include <zephyr/drivers/uart.h>

#define I2S_RX_NODE DT_NODELABEL(i2s_rxtx)

#define SAMPLE_FREQUENCY 16000
#define SAMPLE_BIT_WIDTH 32
#define BYTES_PER_SAMPLE sizeof(int16_t)
#define NUMBER_OF_CHANNELS 1
#define SAMPLES_PER_BLOCK ((SAMPLE_FREQUENCY / 10) * NUMBER_OF_CHANNELS)
#define INITIAL_BLOCKS 2
#define TIMEOUT 1000

#define BLOCK_SIZE (BYTES_PER_SAMPLE * SAMPLES_PER_BLOCK)
#define BLOCK_COUNT (INITIAL_BLOCKS + 2)
K_MEM_SLAB_DEFINE_STATIC(mem_slab, BLOCK_SIZE, BLOCK_COUNT, 4);

const struct device *const i2s_dev_rx = DEVICE_DT_GET(I2S_RX_NODE);
struct i2s_config config;

static int16_t echo_block[SAMPLES_PER_BLOCK];
uint8_t loopCnt = 0;

static void process_block_data(void *mem_block, uint32_t number_of_samples)
{
	for (int i = 0; i < number_of_samples; ++i)
	{
		int16_t *sample = &((int16_t *)mem_block)[i];
		echo_block[i] = *sample;
	  }
	 
}

static bool configure_streams(const struct device *i2s_dev_rx, const struct i2s_config *config)
{
	int ret = i2s_configure(i2s_dev_rx, I2S_DIR_RX, config);
	if (ret == 0)
	{
		printk("Configure Stream Successful.\n");
		return true;
	}
	printk("Failed to configure streams: %d\n", ret);
	return false;
}

static bool trigger_command(const struct device *i2s_dev_rx, enum i2s_trigger_cmd cmd)
{
	int ret = i2s_trigger(i2s_dev_rx, I2S_DIR_RX, cmd);
	if (ret == 0)
	{
		printk("Trigger Command Successful.\n");
		return true;
	}
	printk("Failed to trigger command %d: %d\n", cmd, ret);
	return false;
}

static void i2sStreamInit(void){

	printk("I2S echo sample\n");

	if (!device_is_ready(i2s_dev_rx))
	{
		printk("%s is not ready\n", i2s_dev_rx->name);
		return 0;
	}

	config.word_size = SAMPLE_BIT_WIDTH;
	config.channels = NUMBER_OF_CHANNELS;
	config.format = I2S_FMT_DATA_FORMAT_I2S;
	config.options = I2S_OPT_BIT_CLK_MASTER | I2S_OPT_FRAME_CLK_MASTER;
	config.frame_clk_freq = SAMPLE_FREQUENCY;
	config.mem_slab = &mem_slab;
	config.block_size = BLOCK_SIZE;
	config.timeout = TIMEOUT;

	if (!configure_streams(i2s_dev_rx, &config))
	{
		return 0;
	}

	if (!trigger_command(i2s_dev_rx, I2S_TRIGGER_START))
	{
		return 0;
	}
}



int main(void)
{
	i2sStreamInit();
	printk("Streams started\n");

	while (1)
	{
		void *mem_block;
		uint32_t block_size;
		int ret;

		ret = i2s_read(i2s_dev_rx, &mem_block, &block_size);
		if (ret < 0)
		{
			printk("Failed to read data: %d\n", ret);
			break;
		}

		process_block_data(mem_block, SAMPLES_PER_BLOCK);
		k_mem_slab_free(&mem_slab, mem_block);

	}
	printk("Exiting main loop\n");
	return 0;
}

[Kashyap23]

Hi,I able to solve the issue ,the main thing is by logging data by RTT the buffer size is very low 1024 which is default once I increased size it works this is done by increasing CONFIG_SEGGER_RTT_BUFFER_SIZE_UP,CONFIG_LOG_BUFFER_SIZE

CONFIG_LOG_MODE_OVERFLOW=n

CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=1024

CONFIG_LOG_BUFFER_SIZE=1024

CONFIG_LOG_PROCESS_THREAD_STACK_SIZE=2048

But I dont know what size can I give in that.I increased it randomly by keeping 50k my sampling rate is 16k and each sample 16bits .Can you help me what size do I need to define correctly.

[Elfving]

Great to see that you've gotten further and also shared this solution Kashyap.

Kashyap23 said:

But I dont know what size can I give in that.

I am not sure if I understand the problem, but CONFIG_SEGGER_RTT_BUFFER_SIZE_UP doesn't seem to have a max but several samples increase it from the default 1024 to 4096. CONFIG_LOG_BUFFER_SIZE is often increased to 4096 as well.

Maybe it seems practical at the moment, though logging every single measurement doesn't seem necessary in a final application to me. So I guess this isn't a big issue either way, no matter what you increase it to for the time being.

Regards,

Elfving