Adafruit I2S MEMS Microphone Breakout with the NRF9160 DK

[Nahom Abraha]

Hello,

I am working on a project where I can have Voice over IP on the NRF9160 DK. I am now working with a I2S microphone (https://www.adafruit.com/product/3421) at the moment I have trouble programming I2S. I read the I2S documentation on the zephyr website but I have still trouble understanding it and there is also no example where I can look at. I don't know how to setup the struct device (https://docs.zephyrproject.org/2.0.0/reference/peripherals/i2s.html?highlight=i2s#) that you use in the functions to setup i2s and read/write the buffer. I also don't know which pin i have to connect to the microphone, because the pin names are not the same or can i just connect  to any pin and write in the code to use that pin? If sombody has an I2S example I would really appreciate that. I also need to find a speaker that I can use any suggestions?

Thank you in advance

[Martin Lesund]

Hi Nahom,

You can configure any of the available GPIO pins for the nrf9160.

So you could use the command https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/reference/peripherals/i2s.html#_CPPv413i2s_configureP6device7i2s_dirP10i2s_config and in the .overlay file select which pins it should get. 

See the device tree chapter in the NCS tutorials.

[Nahom Abraha]

Hi Martin,

I am having trouble with the i2s_configure function this is my code and overlay file. I call the recordaudio function in a different file and then I something goes wrong in i2s_init funtion  at i2s_configure. The code stops after the i2s_configure  function.

Thank you in advance

#include <zephyr.h>
#include <device.h>
#include <drivers/i2s.h>
#include <sys/printk.h>
#include <stdbool.h>

#include "microphone.h"
#include "button.h"
#include "udp.h"

#define  MICROPHONE_SAMPLE_FREQ (8000)
#define  MICROPHONE_SAMPLE_PER_FRAME (1)
#define  MICROPHONE_NUM_CHANNELS (1)
#define  MICROPHONE_SAMPLE_BIT_WIDTH (24)
#define  MICROPHONE_SAMPLE_BYTES (2)
#define  MICROPHONE_BLOCK_SIZE (4)
#define  DEVICE_NAME  "I2S_0" 


struct k_mem_slab mic_mem_slab;
struct device *i2s_device;

K_MEM_SLAB_DEFINE(mic_mem_slab,MICROPHONE_BLOCK_SIZE,MICROPHONE_SAMPLE_FREQ,4);

void i2s_init()
{
  struct i2s_config i2s_cfg;
  int config;
  
  i2s_device=device_get_binding(DEVICE_NAME);
  
  i2s_cfg.word_size=MICROPHONE_SAMPLE_BIT_WIDTH;
  i2s_cfg.channels=MICROPHONE_NUM_CHANNELS;
  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=MICROPHONE_SAMPLE_FREQ;
  i2s_cfg.mem_slab=&mic_mem_slab;
  i2s_cfg.block_size=MICROPHONE_BLOCK_SIZE*MICROPHONE_SAMPLE_FREQ;
  i2s_cfg.timeout=K_FOREVER;
  
  config=i2s_configure(i2s_device,I2S_DIR_RX,&i2s_cfg);
  if(config!=0){
      printk("i2s_configure failed with %d error", config);
  }
 

}

void recordaudio(void)
{
  int ret;
  int trigger;
  void *buf;  //uint32_t
  size_t size;
  //configure i2s and start
  i2s_init();
  printk("Starting recording...");
  
  trigger=i2s_trigger(i2s_device,I2S_DIR_RX,I2S_TRIGGER_START); 
  if(trigger!=0){
    printk("TRIGGER_START failed with %d error", trigger);
  }
  
  while(startrecording==true){
    ret=i2s_read(i2s_device,&buf,&size);
    if(ret!=0){
      printk("i2s_read failed with %d error", ret);
    }
  }
    i2s_trigger(i2s_device,I2S_DIR_RX,I2S_TRIGGER_STOP);
    if(trigger!=0){
      printk("TRIGGER_STOP failed with %d error", trigger);
    }

    i2s_trigger(i2s_device,I2S_DIR_RX,I2S_TRIGGER_DROP);
    if(trigger!=0){
      printk("TRIGGER_DROP failed with %d error", trigger);
    }
  printk("Exiting program...");
}

&i2s0 {
	    status = "okay";
        sdout-pin=<8>;
	    lrck-pin=<9>;
        sck-pin=<10>;
        sdin-pin=<11>;
        mck-pin=<12>;
};