used MCLK with GPIO for external compenant clock

Question

Hi, 
 I would like to use MCK as a clock for adc CLK 4Mhz. 
 Could i enable & configure all registers without I2S or PDM peripheral activation? 
 Is there a sample code for MCLK configuration?

Ronan_75 · Accepted Answer

Thank you for your feedback.

i did it with I2S activation, without nominate LRCK,SCLK,DATA, juste MCLK.

Here is the code

#include <nrf.h>
#include <zephyr.h>
#include <device.h>
#include <sys/printk.h>
#include <stdbool.h>
#include <string.h>
#include <nrfx_i2s.h>




static void i2s_clk_init(void);
// a modifier 
#define I2S_MCK_PIN 15 // MCLK pin is GPIO2

#define I2S_DATA_BLOCK_WORDS 512 //How many numbers do we want. time reorded = DATA_BLOCK_WORDS / freq

static uint32_t m_buffer_rx32u[I2S_DATA_BLOCK_WORDS];
static nrfx_i2s_buffers_t i2s_initial_buffers;





// I2S ISR handler
ISR_DIRECT_DECLARE(i2s_isr_handler)
{
  nrfx_i2s_irq_handler();
 ISR_DIRECT_PM();  // PM done after servicing interrupt for best latency
  return 1;         // We should check if scheduling decision should be made
}

// I2S event handler
static void i2s_data_handler(nrfx_i2s_buffers_t const *p_released, uint32_t status)
{
  if (NRFX_I2S_STATUS_NEXT_BUFFERS_NEEDED == status)
  {
    nrfx_i2s_next_buffers_set(&i2s_initial_buffers);
  }
}

/*****************************************************************************
* Function: i2s_clk_init
*
* Description: provide 2.1333333 MHz. reference clock to audio ADC
*
* Parameters: none
*
* Returns: nothing
*****************************************************************************/
static void i2s_clk_init(void)
{
  // the audio clock defaults to 12.288MHz, so we don't need to adjust it

  // configure I2S
  IRQ_DIRECT_CONNECT(I2S0_IRQn, 0, i2s_isr_handler, 0);
  i2s_initial_buffers.p_rx_buffer = m_buffer_rx32u;

  nrfx_i2s_config_t i2s_cfg = NRFX_I2S_DEFAULT_CONFIG(NRFX_I2S_PIN_NOT_USED, NRFX_I2S_PIN_NOT_USED, I2S_MCK_PIN, NRFX_I2S_PIN_NOT_USED, NRFX_I2S_PIN_NOT_USED);
  i2s_cfg.clksrc = NRF_I2S_CLKSRC_PCLK32M ; // audio clock
  i2s_cfg.mck_setup = NRF_I2S_MCK_32MDIV15;
  i2s_cfg.enable_bypass = false;         // bypass division, so we get the raw audio clock
  nrfx_err_t err_code = nrfx_i2s_init(&i2s_cfg, i2s_data_handler);

  if(err_code != NRFX_SUCCESS) 
  {
    printk("Error initializing I2S\n");
    return;
  }
}


void MCLK_Start(void)
{
  nrfx_err_t err_code;
  i2s_clk_init();
    // start i2s
  err_code = nrfx_i2s_start(&i2s_initial_buffers, I2S_DATA_BLOCK_WORDS, 0);
  if (err_code != NRFX_SUCCESS)
  {
    printk("I2S start error\n");
  }
}

void MCLK_stop(void)
{
    // stop i2s
  nrfx_i2s_stop();
}

juste be carful to add the necessary in CMakeLists file

used MCLK with GPIO for external compenant clock

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