Buffers in PDM module

[RajB]

Hi

I'm working with a PDM mic for nRF52832 SDK v17.1 on a project and I have a questions about PDM driver working.

Whats the difference between the buffer pointer in nrfx_pdm_buffer_set(int16_t * buffer, uint16_t buffer_length) and p_evt->buffer_released set after a buffer_request event? Do they point to the same data?

2. How do I access the data in p_evt->buffer_released? I saw this thread but it's for Thingy 52 and another one for the Smart Remote but could you tell me how to implement it in 52832? I tried this code but it only displays zero.

p_buffer_released = p_evt->buffer_released;
pdm_buf = *p_buffer_released;
printf("\n\rOut: %08X",pdm_buf);

 

Unrelated question: nrf_gpio_pin_set() will set a pin to HIGH and nrf_gpio_pin_clear() will set it to LOW. I saw a couple of examples which had it vice versa. Is my assumption right or does nrf_gpio_pin_set() set a pin to LOW?

Regards

Raj

[RajB]

dejans said:

Could you provide more information about the pointers buffer and p_evt->buffer_released? 

This is what I read and I'm trying to understand how the buffer is set. It says another event is generated after a buffer_request event and calling the nrfx_pdm_buffer_set(). I'm looking to reuse the buffer after displaying it. 

dejans said:

Could you specify the examples that you saw?

You can find it here.

[dejans]

Hi,

This example provides code part relevant to setting the buffer

void nrfx_pdm_event_handler(nrfx_pdm_evt_t const * const p_evt)
{
    if(p_evt->buffer_requested)
    {
        nrfx_pdm_buffer_set(pdm_buf, PDM_BUF_SIZE);
    }
    if(p_evt->buffer_released != 0)
    {
        printf("Out: %.2x %.2x\r\n", (uint16_t)pdm_buf[0], (uint16_t)pdm_buf[1]);
    }
}

Best regards,
Dejan