I2S driver

group nrfx_i2s

Inter-IC Sound (I2S) peripheral driver.

Defines

NRFX_I2S_INSTANCE(id): Macro for creating an I2S driver instance.

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

Parameters:

_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.

NRFX_I2S_STATUS_NEXT_BUFFERS_NEEDED: 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).

NRFX_I2S_STATUS_TRANSFER_STOPPED: The I2S peripheral has been stopped and all buffers that were passed to the driver have been released.

Typedefs

typedef nrfy_i2s_buffers_t nrfx_i2s_buffers_t: I2S driver buffers structure.

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.

Note

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.

Note

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_I2S_STATUS_NEXT_BUFFERS_NEEDED
NRFX_I2S_STATUS_TRANSFER_STOPPED

Functions

nrfx_err_t nrfx_i2s_init(nrfx_i2s_t const *p_instance, nrfx_i2s_config_t const *p_config, nrfx_i2s_data_handler_t handler)

Function for initializing the I2S driver.

Parameters:

p_instance – [in] Pointer to the driver instance structure.
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(nrfx_i2s_t const *p_instance)

Function for uninitializing the I2S driver.

Parameters:

p_instance – [in] Pointer to the driver instance structure.

nrfx_err_t nrfx_i2s_start(nrfx_i2s_t const *p_instance, 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.

Note

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.

Parameters:

p_instance – [in] Pointer to the driver instance structure.
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_t const *p_instance, 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.