Using PDM microphone on nrf5340

[BrianW]

I am developing a board with the nrf5340, and using a PDM microphone for audio input.

I have used the same microphone on the nrf52832 with the nrf PDM driver with success.

However, on the nrf5340 under Zephyr, I get the following error as soon as I start the PDM recording:

[00:00:33.402,099] <inf> base: pdmmgr : rec start turning power on
[00:00:33.409,240] <inf> base: pdmmgr : rec start configuring pinctrl
[00:00:33.416,137] <inf> base: pdmmgr : rec start enabling irq
[00:00:33.422,424] <inf> base: pdmmgr : rec start nrfx_pdm_init()
[00:00:33.428,985] <inf> base: pdmmgr : rec start nrfx_pdm_start()
[00:00:33.481,323] <err> os: >>> ZEPHYR FATAL ERROR 1: Unhandled interrupt on CPU 0
[00:00:33.489,624] <err> os: Current thread: 0x200052c8 (main)
[00:00:33.496,124] <err> os: Halting system

This occurs when I call nrfx_pdm_start()...

My code:

    log_info("pdmmgr : rec start turning power on");

    // turn on the mic power

    gpiomgr_write(ctx->pin_pdm_en, 1);

    ctx->rec_cb = cb_fn;

    // microphone config : only 1 hw configured as L, so mono left channel (clock on rising edge)

    nrfx_pdm_config_t config1 = {

        .mode               = NRF_PDM_MODE_MONO,

        .edge               = NRF_PDM_EDGE_LEFTRISING,

        .clock_freq         = NRF_PDM_FREQ_1032K,

        .gain_l             = NRF_PDM_GAIN_MAXIMUM,

        .gain_r             = NRF_PDM_GAIN_MAXIMUM,

        .interrupt_priority = NRFX_PDM_DEFAULT_CONFIG_IRQ_PRIORITY,

        .skip_gpio_cfg      = true,            /* use DTS via pinctrl_apply_state() */

        .skip_psel_cfg      = true

    };

//    config1.clk_pin = gpiomgr_get_pin(ctx->pin_sck);

//    config1.din_pin = gpiomgr_get_pin(ctx->pin_sdio);

    log_info("pdmmgr : rec start configuring pinctrl");

    uint32_t errcode = pinctrl_apply_state(PINCTRL_DT_DEV_CONFIG_GET(PDM_NL), PINCTRL_STATE_DEFAULT);

    if (errcode!=0) {

        log_warn("pdmmgr : PDM pin setup from DTS fails, errcode %d",errcode);

        return false;

    }

    log_info("pdmmgr : rec start enabling irq");

    irq_enable(DT_IRQN(PDM_NL));

    log_info("pdmmgr : rec start nrfx_pdm_init()");

    errcode = nrfx_pdm_init(&config1, _drv_pdm_handler);

    if (errcode!=NRFX_SUCCESS) {

        log_warn("pdmmgr: error %d trying to init pdm record",errcode);

        gpiomgr_write(ctx->pin_pdm_en, 0);

        return false;

    }

    ctx->audio_rec_buf = data;

    ctx->audio_rec_buf_sz = dlen;

    ctx->voice_detected = false;   // no voice detected

    ctx->rec_active_buffer = 0;       // no active buffer yet (unlike play, driver will immediately call the handler cb to get 1st buffer)

    ctx->rec_data_nsamples = 0;     // no data yet

    log_info("pdmmgr : rec start nrfx_pdm_start()");

    errcode = nrfx_pdm_start();

    if (errcode!=NRFX_SUCCESS) {

        log_warn("pdmmgr: error %d trying to start pdm record",errcode);

        nrfx_pdm_uninit();

        gpiomgr_write(ctx->pin_pdm_en, 0);

        return false;

    }

What am I not initialising correctly?