PDM driver

group nrfx_pdm

Pulse Density Modulation (PDM) peripheral driver.

Defines

NRFX_PDM_MAX_BUFFER_SIZE

Maximum supported PDM buffer size.

NRFX_PDM_DEFAULT_EXTENDED_RATIO_CONFIG

PDM additional ratio configuration.

NRFX_PDM_DEFAULT_EXTENDED_MCLKSRC_CONFIG

PDM additional master clock source configuration.

NRFX_PDM_DEFAULT_CONFIG(_pin_clk, _pin_din)

PDM driver default configuration.

This configuration sets up PDM with the following options:

  • mono mode

  • data sampled on the clock falling edge

  • frequency: 1.032 MHz

  • standard gain

Parameters

  • _pin_clk – [in] CLK output pin.

  • _pin_din – [in] DIN input pin.

Typedefs

typedef void (*nrfx_pdm_event_handler_t)(nrfx_pdm_evt_t const *p_evt)

Handler for the PDM interface ready events.

This event handler is called on a buffer request, an error or when a buffer is full and ready to be processed.

Parameters

  • p_evt – [in] Pointer to the PDM event structure.

Enums

enum nrfx_pdm_error_t

PDM error type.

Values:

enumerator NRFX_PDM_NO_ERROR

No error.

enumerator NRFX_PDM_ERROR_OVERFLOW

Overflow error.

Functions

nrfx_err_t nrfx_pdm_init(nrfx_pdm_config_t const *p_config, nrfx_pdm_event_handler_t event_handler)

Function for initializing the PDM interface.

Parameters

  • p_config – [in] Pointer to the structure with the initial configuration.

  • event_handler – [in] Event handler provided by the user. Cannot be NULL.

Returns NRFX_SUCCESS

Initialization was successful.

Returns NRFX_ERROR_INVALID_STATE

The driver is already initialized.

Returns NRFX_ERROR_INVALID_PARAM

Invalid configuration was specified.

void nrfx_pdm_uninit(void)

Function for uninitializing the PDM interface.

This function stops PDM sampling, if it is in progress.

NRFX_STATIC_INLINE uint32_t nrfx_pdm_task_address_get(nrf_pdm_task_t task)

Function for getting the address of a PDM interface task.

Parameters

  • task – [in] Task.

Returns

Task address.

NRFX_STATIC_INLINE bool nrfx_pdm_enable_check(void)

Function for getting the state of the PDM interface.

Returns true

The PDM interface is enabled.

Returns false

The PDM interface is disabled.

nrfx_err_t nrfx_pdm_start(void)

Function for starting the PDM sampling.

Returns NRFX_SUCCESS

Sampling was started successfully or was already in progress.

Returns NRFX_ERROR_BUSY

Previous start/stop operation is in progress.

nrfx_err_t nrfx_pdm_stop(void)

Function for stopping the PDM sampling.

When this function is called, the PDM interface is stopped after finishing the current frame. The event handler function might be called once more after calling this function.

Returns NRFX_SUCCESS

Sampling was stopped successfully or was already stopped before.

Returns NRFX_ERROR_BUSY

Previous start/stop operation is in progress.

nrfx_err_t nrfx_pdm_buffer_set(int16_t *buffer, uint16_t buffer_length)

Function for supplying the sample buffer.

Call this function after every buffer request event.

Parameters

  • buffer – [in] Pointer to the receive buffer. Cannot be NULL.

  • buffer_length – [in] Length of the receive buffer in 16-bit words.

Returns NRFX_SUCCESS

The buffer was applied successfully.

Returns NRFX_ERROR_BUSY

The buffer was already supplied or the peripheral is currently being stopped.

Returns NRFX_ERROR_INVALID_STATE

The driver was not initialized.

Returns NRFX_ERROR_INVALID_PARAM

Invalid parameters were provided.

struct nrfx_pdm_evt_t
#include <nrfx_pdm.h>

PDM event structure.

Public Members

bool buffer_requested

Buffer request flag.

int16_t *buffer_released

Pointer to the released buffer. Can be NULL.

nrfx_pdm_error_t error

Error type.

struct nrfx_pdm_config_t
#include <nrfx_pdm.h>

PDM interface driver configuration structure.

Public Members

nrf_pdm_mode_t mode

Interface operation mode.

nrf_pdm_edge_t edge

Sampling mode.

uint8_t pin_clk

CLK pin.

uint8_t pin_din

DIN pin.

nrf_pdm_freq_t clock_freq

Clock frequency.

nrf_pdm_gain_t gain_l

Left channel gain.

nrf_pdm_gain_t gain_r

Right channel gain.

uint8_t interrupt_priority

Interrupt priority.