PDM example in SDK 15.3.0

[sarnab]

I cannot find an example project for using the PDM module on SDK 15.3.0. Can you please direct me to where I will be able to find such an example project?

Thank you.

[sara]

Hi, Sarnab I too, have the same question as yours. So how far have you reached?I tried the example which Simonr have provided the link for the example. But I am getting the following errors:

undefined reference to `nrfx_pdm_init' and undefined reference to `nrfx_pdm_start'

@ Simonr if you have any idea about how can I solve the above errors?

[sarnab]

Hi Sara, I was able to get it working though I have not extensively tested if the data is valid. To get the nrfx_pdm_xxx() functions you have to include nrfx_pdm.h in your project. Hope that helps. Also if you are able to get meaningful data please let me know what you did!

[sara]

Yes, I have included the nrfx_pdm.h but getting nrfx_pdm_init undefined and nrfx_pdm_start undefined references. For that what should I do?

[sarnab]

when you right click on nrfx_pdm.h and select 'go to definition' does it take you to the file? 

[sara]

yes it takes me to file to the file and when I right click on nrf_drv_pdm_start it takes me to its macro definition in nrfx_drv_pdm.h  as  nrfx_pdm_start 

[sarnab]

Hmm, that is strange. What IDE are you using? I am on Segger Embedded Studio (SES). Are you sure your include paths are set correctly?

[sara]

yes I have set the paths correctly.I have added #include "nrf_drv_pdm.h" in main .c file , then added the following in the   .emProject file <file file_name="../../../../../../modules/nrfx/drivers/src/nrfx_pdm.c" />  is there anything else I am missing? 

And I m using SES too. SDK ver 15.3.0

[sara]

The error was solved, I had not enabled 

#ifndef PDM_ENABLED
#define PDM_ENABLED 1

I programmed the code but now question is how should i check whether pdm is working properly or not? I am not storing anything in flash. For now, I just need the data of pdm so how should I test it to get the results

static void bsp_event_handler(bsp_event_t event)
{
    ret_code_t err_code;

    switch (event)
    {
        case BSP_EVENT_SLEEP:
            sleep_mode_enter();
            break; // BSP_EVENT_SLEEP

        case BSP_EVENT_DISCONNECT:
            err_code = sd_ble_gap_disconnect(m_conn_handle,
                                             BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
            if (err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            break; // BSP_EVENT_DISCONNECT

        case BSP_EVENT_WHITELIST_OFF:
            if (m_conn_handle == BLE_CONN_HANDLE_INVALID)
            {
                err_code = ble_advertising_restart_without_whitelist(&m_advertising);
                if (err_code != NRF_ERROR_INVALID_STATE)
                {
                    APP_ERROR_CHECK(err_code);
                }
            }
            break; // BSP_EVENT_KEY_0
          case BSP_EVENT_KEY_1:
            NRF_LOG_INFO("\n Press Button key 1\n");
            NRF_LOG_INFO("\n Erase the flash content !!\n");
//            err_code = pcm_pstorage_eraseall();
//            APP_ERROR_CHECK(err_code);
            break;

         case BSP_EVENT_KEY_2:
            NRF_LOG_INFO("\n Start:PDM --> PCM\n");
            err_code =  nrf_drv_pdm_start(); 
            APP_ERROR_CHECK(err_code);
            break;

         case BSP_EVENT_KEY_3:
            NRF_LOG_INFO("\n Stop:PDM --> PCM\n");
            // stop audio sample
            nrf_drv_pdm_stop();
            break;

        default:
            break;
    }
}









static void drv_audio_pdm_event_handler(uint32_t *p_buffer, uint16_t length)
{
	m_buffer_handler((int16_t *)p_buffer, length);
        int i;
//        for(i=0;i<= length;i++)
//        {
//          NRF_LOG_INFO("%s ",&p_buffer[i]);
//        }
//        NRF_LOG_INFO("\n ");
          NRF_LOG_INFO("pdm event handler \n");

}


uint32_t drv_audio_init(drv_audio_buffer_handler_t buffer_handler)
{
//    nrf_drv_pdm_config_t pdm_cfg = NRF_DRV_PDM_DEFAULT_CONFIG(CONFIG_IO_PDM_CLK,
//                                                              CONFIG_IO_PDM_DATA,
//                                                              m_pdm_buff[0],
//                                                              m_pdm_buff[1],
//                                                              CONFIG_PDM_BUFFER_SIZE_SAMPLES);
    nrf_drv_pdm_config_t pdm_cfg = NRF_DRV_PDM_DEFAULT_CONFIG(CONFIG_IO_PDM_CLK,CONFIG_IO_PDM_DATA);
    
    if (buffer_handler == NULL)
    {
        return NRF_ERROR_INVALID_PARAM;
    }
    
    m_buffer_handler    = buffer_handler;
    pdm_cfg.gain_l      = CONFIG_PDM_GAIN;
    pdm_cfg.gain_r      = CONFIG_PDM_GAIN;
    

    return nrf_drv_pdm_init(&pdm_cfg, drv_audio_pdm_event_handler);
}










int main(void)
{
    bool erase_bonds;

    // Initialize.
    log_init();
    timers_init();
    buttons_leds_init(&erase_bonds);
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    advertising_init();
    services_init();
    conn_params_init();
    peer_manager_init();

    // Start execution.
    NRF_LOG_INFO("Template example started.");
    application_timers_start();

//    advertising_start(erase_bonds);
    uint32_t err_code;
    err_code = drv_audio_init(drv_audio_pdm_event_handler);
    APP_ERROR_CHECK(err_code);
    
    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
    }
}

.For your reference, I am attaching my code snippet

I have checked the clk pin on Oscilloscope , the clock is not being generated.In order to generate clk at pin number 22 of nrf52 DK board should I define pin clk as #define CONFIG_IO_PDM_CLK 0x22 or 0x16 (hex value of 22 )instead of 0x22?

[sara]

And when I read the pdm documentation it says I need to change the PSEL.CLK register value? Then how should I do it and with what value? same for PSEL.DIN register. I am confused a lot. Please suggest me the solution to all my doubts.