TWIM driver

group nrfx_twim

Two Wire Interface Master with EasyDMA (TWIM) peripheral driver.

Defines

NRFX_TWIM_INSTANCE(id)

Macro for creating a TWI master driver instance.

NRFX_TWIM_DEFAULT_CONFIG(_pin_scl, _pin_sda)

TWIM driver default configuration.

This configuration sets up TWIM with the following options:

  • clock frequency: 100 kHz

  • disable bus holding after uninit

Parameters
  • _pin_scl[in] SCL pin.

  • _pin_sda[in] SDA pin.

NRFX_TWIM_FLAG_TX_POSTINC

Flag indicating that TX buffer address will be incremented after the transfer.

NRFX_TWIM_FLAG_RX_POSTINC

Flag indicating that RX buffer address will be incremented after the transfer.

NRFX_TWIM_FLAG_NO_XFER_EVT_HANDLER

Flag indicating that the interrupt after each transfer will be suppressed, and the event handler will not be called.

NRFX_TWIM_FLAG_HOLD_XFER

Flag indicating that the transfer will be set up, but not started.

NRFX_TWIM_FLAG_REPEATED_XFER

Flag indicating that the transfer will be executed multiple times.

NRFX_TWIM_FLAG_TX_NO_STOP

Flag indicating that the TX transfer will not end with a stop condition.

NRFX_TWIM_FLAG_NO_SPURIOUS_STOP_CHECK

Flag indicating that checks for spurious STOP condition will not be performed.

NRFX_TWIM_XFER_DESC_TX(addr, p_data, length)

Macro for setting the TX transfer descriptor.

NRFX_TWIM_XFER_DESC_RX(addr, p_data, length)

Macro for setting the RX transfer descriptor.

NRFX_TWIM_XFER_DESC_TXRX(addr, p_tx, tx_len, p_rx, rx_len)

Macro for setting the TX-RX transfer descriptor.

NRFX_TWIM_XFER_DESC_TXTX(addr, p_tx, tx_len, p_tx2, tx_len2)

Macro for setting the TX-TX transfer descriptor.

Typedefs

typedef void (*nrfx_twim_evt_handler_t)(nrfx_twim_evt_t const *p_event, void *p_context)

TWI event handler prototype.

Enums

enum nrfx_twim_evt_type_t

TWI master driver event types.

Values:

enumerator NRFX_TWIM_EVT_DONE

Transfer completed event.

enumerator NRFX_TWIM_EVT_ADDRESS_NACK

Error event: NACK received after sending the address.

enumerator NRFX_TWIM_EVT_DATA_NACK

Error event: NACK received after sending a data byte.

enumerator NRFX_TWIM_EVT_OVERRUN

Error event: The unread data is replaced by new data.

enumerator NRFX_TWIM_EVT_BUS_ERROR

Error event: An unexpected transition occurred on the bus.

enum nrfx_twim_xfer_type_t

TWI master driver transfer types.

Values:

enumerator NRFX_TWIM_XFER_TX

TX transfer.

enumerator NRFX_TWIM_XFER_RX

RX transfer.

enumerator NRFX_TWIM_XFER_TXRX

TX transfer followed by RX transfer with repeated start.

enumerator NRFX_TWIM_XFER_TXTX

TX transfer followed by TX transfer with repeated start.

Functions

nrfx_err_t nrfx_twim_init(nrfx_twim_t const *p_instance, nrfx_twim_config_t const *p_config, nrfx_twim_evt_handler_t event_handler, void *p_context)

Function for initializing the TWI driver instance.

Warning

On nRF5340, 1 MHz setting is supported only on the dedicated pins. See the chapter Pin assignments in the Product Specification.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

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

  • event_handler[in] Event handler provided by the user. If NULL, blocking mode is enabled.

  • p_context[in] Context passed to event handler.

Return values
  • NRFX_SUCCESS – Initialization was successful.

  • NRFX_ERROR_INVALID_STATE – The driver is in invalid state.

  • NRFX_ERROR_INVALID_PARAM – Requested frequency is not available on the specified pins.

  • NRFX_ERROR_BUSY – Some other peripheral with the same instance ID is already in use. This is possible only if Peripheral Resource Sharing (PRS) module is enabled.

void nrfx_twim_uninit(nrfx_twim_t const *p_instance)

Function for uninitializing the TWI instance.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

void nrfx_twim_enable(nrfx_twim_t const *p_instance)

Function for enabling the TWI instance.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

void nrfx_twim_disable(nrfx_twim_t const *p_instance)

Function for disabling the TWI instance.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

nrfx_err_t nrfx_twim_xfer(nrfx_twim_t const *p_instance, nrfx_twim_xfer_desc_t const *p_xfer_desc, uint32_t flags)

Function for performing a TWI transfer.

The following transfer types can be configured (nrfx_twim_xfer_desc_t::type):

Additional options are provided using the flags parameter:

If nrfx_twim_xfer_desc_t::type is set to NRFX_TWIM_XFER_TX and the NRFX_TWIM_FLAG_TX_NO_STOP and NRFX_TWIM_FLAG_REPEATED_XFER flags are set, two tasks must be used to trigger a transfer: TASKS_RESUME followed by TASKS_STARTTX. If no stop condition is generated, TWIM is in SUSPENDED state. Therefore, it must be resumed before the transfer can be started.

Note

TX-RX and TX-TX transfers are supported only in non-blocking mode.

Note

Peripherals using EasyDMA (including TWIM) 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_xfer_desc[in] Pointer to the transfer descriptor.

  • flags[in] Transfer options (0 for default settings).

Return values
  • NRFX_SUCCESS – The procedure is successful.

  • NRFX_ERROR_BUSY – The driver is not ready for a new transfer.

  • NRFX_ERROR_NOT_SUPPORTED – The provided parameters are not supported.

  • NRFX_ERROR_INTERNAL – An unexpected transition occurred on the bus.

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

  • NRFX_ERROR_DRV_TWI_ERR_OVERRUN – The unread data is replaced by new data.

  • NRFX_ERROR_DRV_TWI_ERR_ANACK – NACK is received after sending the address.

  • NRFX_ERROR_DRV_TWI_ERR_DNACK – NACK is received after sending a data byte.

bool nrfx_twim_is_busy(nrfx_twim_t const *p_instance)

Function for checking the TWI driver state.

Parameters
  • p_instance[in] TWI instance.

Return values
  • true – The TWI driver is currently busy performing a transfer.

  • false – The TWI driver is ready for a new transfer.

uint32_t nrfx_twim_start_task_get(nrfx_twim_t const *p_instance, nrfx_twim_xfer_type_t xfer_type)

Function for returning the address of a TWIM start task.

This function is to be used if nrfx_twim_xfer was called with the flag NRFX_TWIM_FLAG_HOLD_XFER. In that case, the transfer is not started by the driver, but it must be started externally by PPI.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

  • xfer_type[in] Transfer type used in the last call of the nrfx_twim_xfer function.

Returns

Start task address (TX or RX) depending on the value of xfer_type.

uint32_t nrfx_twim_stopped_event_get(nrfx_twim_t const *p_instance)

Function for returning the address of a STOPPED TWIM event.

A STOPPED event can be used to detect the end of a transfer if the NRFX_TWIM_FLAG_NO_XFER_EVT_HANDLER option is used.

Parameters
  • p_instance[in] Pointer to the driver instance structure.

Returns

STOPPED event address.

NRFX_STATIC_INLINE nrfx_err_t nrfx_twim_bus_recover(uint32_t scl_pin, uint32_t sda_pin)

Function for recovering the bus.

This function checks if the bus is not stuck because of a slave holding the SDA line in the low state, and if needed it performs required number of pulses on the SCL line to make the slave release the SDA line. Finally, the function generates a STOP condition on the bus to put it into a known state.

Note

This function can be used only if the TWIM driver is uninitialized.

Parameters
  • scl_pin[in] SCL pin number.

  • sda_pin[in] SDA pin number.

Return values
  • NRFX_SUCCESS – Bus recovery was successful.

  • NRFX_ERROR_INTERNAL – Bus recovery failed.

struct nrfx_twim_t
#include <nrfx_twim.h>

Structure for the TWI master driver instance.

Public Members

NRF_TWIM_Type *p_twim

Pointer to a structure with TWIM registers.

uint8_t drv_inst_idx

Index of the driver instance. For internal use only.

struct nrfx_twim_config_t
#include <nrfx_twim.h>

Structure for the TWI master driver instance configuration.

Public Members

uint32_t scl

SCL pin number.

uint32_t sda

SDA pin number.

nrf_twim_frequency_t frequency

TWIM frequency.

uint8_t interrupt_priority

Interrupt priority.

bool hold_bus_uninit

Hold pull up state on GPIO pins after uninit.

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.

Note

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_twim_xfer_desc_t
#include <nrfx_twim.h>

Structure for a TWI transfer descriptor.

Public Members

nrfx_twim_xfer_type_t type

Type of transfer.

uint8_t address

Slave address.

size_t primary_length

Number of bytes transferred.

size_t secondary_length

Number of bytes transferred.

uint8_t *p_primary_buf

Pointer to transferred data.

uint8_t *p_secondary_buf

Pointer to transferred data.

struct nrfx_twim_evt_t
#include <nrfx_twim.h>

Structure for a TWI event.

Public Members

nrfx_twim_evt_type_t type

Event type.

nrfx_twim_xfer_desc_t xfer_desc

Transfer details.