I2S driver

group nrfx_i2s

Inter-IC Sound (I2S) peripheral driver.



This value can be provided instead of a pin number for the signals SDOUT, SDIN, and MCK to specify that a given signal is not used and therefore does not need to be connected to a pin.


I2S additional clock source configuration.

NRFX_I2S_DEFAULT_CONFIG(_pin_sck, _pin_lrck, _pin_mck, _pin_sdout, _pin_sdin)

I2S driver default configuration.

This configuration sets up I2S with the following options:

  • master mode

  • i2s data format

  • left alignment

  • sample width 16 bit

  • left channel enabled

  • MCK frequency 4 MHz

  • LRCK frequency 125 kHz

  • _pin_sck[in] SCK pin number.

  • _pin_lrck[in] LRCK pin number.

  • _pin_mck[in] MCK pin number.

  • _pin_sdout[in] SDOUT pin number.

  • _pin_sdin[in] SDIN pin number.


The application must provide buffers that are to be used in the next part of the transfer. A call to nrfx_i2s_next_buffers_set must be done before the currently used buffers are completely processed (that is, the time remaining for supplying the next buffers depends on the used size of the buffers).


The I2S peripheral has been stopped and all buffers that were passed to the driver have been released.


typedef void (*nrfx_i2s_data_handler_t)(nrfx_i2s_buffers_t const *p_released, uint32_t status)

I2S driver data handler type.

A data handling function of this type must be specified during the initialization of the driver. The driver will call this function when it finishes using buffers passed to it by the application, and when it needs to be provided with buffers for the next part of the transfer.


The p_released pointer passed to this function is temporary and will be invalid after the function returns, hence it cannot be stored and used later. If needed, the pointed content (that is, buffers pointers) must be copied instead.


Since the peripheral is stopped asynchronously, buffers that are released after the call to nrfx_i2s_stop are not used entirely. In this case, only a part (if any) of the TX buffer has been actually transmitted and only a part (if any) of the RX buffer is filled with received data.

Param p_released

[in] Pointer to a structure with pointers to buffers passed previously to the driver that will no longer be accessed by it (they can be now safely released or used for another purpose, in particular for a next part of the transfer). This pointer will be NULL if the application did not supply the buffers for the next part of the transfer (via a call to nrfx_i2s_next_buffers_set) since the previous time the data handler signaled such need. This means that data corruption occurred (the previous buffers are used for the second time) and no buffers can be released at the moment. Both pointers in this structure are NULL when the handler is called for the first time after a transfer is started, because no data has been transferred yet at this point. In all successive calls, the pointers specify what has been sent (TX) and what has been received (RX) in the part of the transfer that has just been completed (provided that a given direction is enabled, see nrfx_i2s_start).

Param status

[in] Bit field describing the current status of the transfer. It can be 0 or a combination of the following flags:


nrfx_err_t nrfx_i2s_init(nrfx_i2s_config_t const *p_config, nrfx_i2s_data_handler_t handler)

Function for initializing the I2S driver.

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

  • handler[in] Data handler provided by the user. Must not be NULL.

Return values
  • NRFX_SUCCESS – Initialization was successful.

  • NRFX_ERROR_INVALID_STATE – The driver was already initialized.

  • NRFX_ERROR_INVALID_PARAM – The requested combination of configuration options is not allowed by the I2S peripheral.

void nrfx_i2s_uninit(void)

Function for uninitializing the I2S driver.

nrfx_err_t nrfx_i2s_start(nrfx_i2s_buffers_t const *p_initial_buffers, uint16_t buffer_size, uint8_t flags)

Function for starting the continuous I2S transfer.

The I2S data transfer can be performed in one of three modes: RX (reception) only, TX (transmission) only, or in both directions simultaneously. The mode is selected by specifying a proper buffer for a given direction in the call to this function or by passing NULL instead if this direction is to be disabled.

The length of the buffer (which is a common value for RX and TX if both directions are enabled) is specified in 32-bit words. One 32-bit memory word can either contain four 8-bit samples, two 16-bit samples, or one right-aligned 24-bit sample sign-extended to a 32-bit value. For a detailed memory mapping for different supported configurations, see the Product Specification.


Peripherals using EasyDMA (including I2S) require the transfer buffers to be placed in the Data RAM region. If this condition is not met, this function will fail with the error code NRFX_ERROR_INVALID_ADDR.

  • p_initial_buffers[in] Pointer to a structure specifying the buffers to be used in the initial part of the transfer (buffers for all consecutive parts are provided through the data handler).

  • buffer_size[in] Size of the buffers (in 32-bit words). Must not be 0.

  • flags[in] Transfer options (0 for default settings). Currently, no additional flags are available.

Return values
  • NRFX_SUCCESS – The operation was successful.

  • NRFX_ERROR_INVALID_STATE – Transfer was already started or the driver has not been initialized.

  • NRFX_ERROR_INVALID_ADDR – The provided buffers are not placed in the Data RAM region.

nrfx_err_t nrfx_i2s_next_buffers_set(nrfx_i2s_buffers_t const *p_buffers)

Function for supplying the buffers to be used in the next part of the transfer.

The application must call this function when the data handler receives NRFX_I2S_STATUS_NEXT_BUFFERS_NEEDED in the status parameter. The call can be done immediately from the data handler function or later, but it has to be done before the I2S peripheral finishes processing the buffers supplied previously. Otherwise, data corruption will occur.

  • p_buffers[in] Pointer to a structure specifying the buffers to be used in the upcoming part of the transfer.

Return values
  • NRFX_SUCCESS – If the operation was successful.

  • NRFX_ERROR_INVALID_STATE – If the buffers were already supplied or the peripheral is currently being stopped.

void nrfx_i2s_stop(void)

Function for stopping the I2S transfer.

struct nrfx_i2s_config_t
#include <nrfx_i2s.h>

I2S driver configuration structure.

Public Members

uint8_t sck_pin

SCK pin number.

uint8_t lrck_pin

LRCK pin number.

uint8_t mck_pin

MCK pin number.

Optional. Use NRFX_I2S_PIN_NOT_USED if this signal is not needed.

uint8_t sdout_pin

SDOUT pin number.

Optional. Use NRFX_I2S_PIN_NOT_USED if this signal is not needed.

uint8_t sdin_pin

SDIN pin number.

Optional. Use NRFX_I2S_PIN_NOT_USED if this signal is not needed.

uint8_t irq_priority

Interrupt priority.

nrf_i2s_mode_t mode

Mode of operation.

nrf_i2s_format_t format

Frame format.

nrf_i2s_align_t alignment

Alignment of sample within a frame.

nrf_i2s_swidth_t sample_width

Sample width.

nrf_i2s_channels_t channels

Enabled channels.

nrf_i2s_mck_t mck_setup

Master clock setup.

nrf_i2s_ratio_t ratio

MCK/LRCK ratio.

bool skip_gpio_cfg

Skip GPIO configuration of pins.

When set to true, the driver does not modify any GPIO parameters of the used pins. Those parameters are supposed to be configured externally before the driver is initialized.

bool skip_psel_cfg

Skip pin selection configuration.

When set to true, the driver does not modify pin select registers in the peripheral. Those registers are supposed to be set up externally before the driver is initialized.


When both GPIO configuration and pin selection are to be skipped, the structure fields that specify pins can be omitted, as they are ignored anyway.

struct nrfx_i2s_buffers_t
#include <nrfx_i2s.h>

I2S driver buffers structure.

Public Members

uint32_t *p_rx_buffer

Pointer to the buffer for received data.

uint32_t const *p_tx_buffer

Pointer to the buffer with data to be sent.