TWIS driver

group nrfx_twis

Two Wire Interface Slave with EasyDMA (TWIS) peripheral driver.

Defines

NRFX_TWIS_INSTANCE(id)

Macro for creating a TWIS driver instance.

NRFX_TWIS_DEFAULT_CONFIG(_pin_scl, _pin_sda, _addr)

TWIS driver default configuration.

This configuration sets up TWIS with the following options:

  • second slave address disabled

  • SCL pull-up disabled

  • SDA pull-up disabled

Parameters

  • _pin_scl – [in] SCL pin.

  • _pin_sda – [in] SDA pin.

  • _addr – [in] Slave address on TWI bus.

Typedefs

typedef void (*nrfx_twis_event_handler_t)(nrfx_twis_evt_t const *p_event)

TWI slave event callback function type.

Param p_event

[in] Event information structure.

Enums

enum nrfx_twis_evt_type_t

Event callback function event definitions.

Values:

enumerator NRFX_TWIS_EVT_READ_REQ

Read request detected.

If there is no buffer prepared, buf_req flag in the even will be set. Call then nrfx_twis_tx_prepare to give parameters for buffer.

enumerator NRFX_TWIS_EVT_READ_DONE

Read request finished - free any data.

enumerator NRFX_TWIS_EVT_READ_ERROR

Read request finished with error.

enumerator NRFX_TWIS_EVT_WRITE_REQ

Write request detected.

If there is no buffer prepared, buf_req flag in the even will be set. Call then nrfx_twis_rx_prepare to give parameters for buffer.

enumerator NRFX_TWIS_EVT_WRITE_DONE

Write request finished - process data.

enumerator NRFX_TWIS_EVT_WRITE_ERROR

Write request finished with error.

enumerator NRFX_TWIS_EVT_GENERAL_ERROR

Error that happens not inside WRITE or READ transaction.

enum nrfx_twis_error_t

Possible error sources.

This is flag enum - values from this enum can be connected using logical or operator.

Note

You can use directly nrf_twis_error_t. Error type enum is redefined here because of possible future extension (eg. supporting timeouts and synchronous mode).

Values:

enumerator NRFX_TWIS_ERROR_OVERFLOW

RX buffer overflow detected, and prevented.

enumerator NRFX_TWIS_ERROR_DATA_NACK

NACK sent after receiving a data byte.

enumerator NRFX_TWIS_ERROR_OVERREAD

TX buffer over-read detected, and prevented.

enumerator NRFX_TWIS_ERROR_UNEXPECTED_EVENT

Unexpected event detected by state machine.

Functions

nrfx_err_t nrfx_twis_init(nrfx_twis_t const *p_instance, nrfx_twis_config_t const *p_config, nrfx_twis_event_handler_t event_handler)

Function for initializing the TWIS driver instance.

Function initializes and enables the TWIS driver.

Attention

After driver initialization enable it with nrfx_twis_enable.

Attention

p_instance has to be global object. It will be used by interrupts so make it sure that object is not destroyed when function is leaving.

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.

Return values

  • NRFX_SUCCESS – Initialization is successful.

  • NRFX_ERROR_INVALID_STATE – The driver is already initialized.

  • NRFX_ERROR_BUSY – Some other peripheral with the same instance ID is already in use. This is possible only if NRFX_PRS_ENABLED is set to a value other than zero.

void nrfx_twis_uninit(nrfx_twis_t const *p_instance)

Function for uninitializing the TWIS driver instance.

Function uninitializes the peripheral and resets all registers to default values.

Note

It is safe to call nrfx_twis_uninit even before initialization. Actually, nrfx_twis_init function calls this function to make sure that TWIS state is known.

Note

If TWIS driver was in uninitialized state before calling this function, the selected pins would not be reset to default configuration.

Parameters

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

void nrfx_twis_enable(nrfx_twis_t const *p_instance)

Function for enabling the TWIS instance.

This function enables the TWIS instance. Function defined if there is need for dynamically enabling and disabling the peripheral. Use nrfx_twis_enable and nrfx_twis_disable functions. They do not change any configuration registers.

Parameters

  • p_instance – Pointer to the driver instance structure.

void nrfx_twis_disable(nrfx_twis_t const *p_instance)

Function for disabling the TWIS instance.

This function disables the TWIS instance, which gives possibility to turn off the TWIS while holding configuration done by nrfx_twis_init.

Parameters

  • p_instance – Pointer to the driver instance structure.

uint32_t nrfx_twis_error_get_and_clear(nrfx_twis_t const *p_instance)

Function for getting and clearing the last error flags.

This function gets the information about errors. This is also the only possibility to exit from the error substate of the internal state machine.

Attention

This function clears error state and flags.

Parameters

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

Returns

Error flags defined in nrfx_twis_error_t.

nrfx_err_t nrfx_twis_tx_prepare(nrfx_twis_t const *p_instance, void const *p_buf, size_t size)

Function for preparing the data for sending.

This function is to be used in response to the NRFX_TWIS_EVT_READ_REQ event.

Attention

Transmission buffer must be placed in RAM.

Note

Peripherals using EasyDMA (including TWIS) 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_buf – [in] Transmission buffer.

  • size – [in] Maximum number of bytes that master may read from buffer given.

Return values

  • NRFX_SUCCESS – The preparation finished properly.

  • NRFX_ERROR_INVALID_ADDR – The given p_buf is not placed inside the RAM.

  • NRFX_ERROR_INVALID_LENGTH – There is a wrong value in the size parameter.

  • NRFX_ERROR_INVALID_STATE – The module is not initialized or not enabled.

NRFX_STATIC_INLINE size_t nrfx_twis_tx_amount(nrfx_twis_t const *p_instance)

Function for getting the number of transmitted bytes.

This function returns the number of bytes sent. This function can be called after NRFX_TWIS_EVT_READ_DONE or NRFX_TWIS_EVT_READ_ERROR events.

Parameters

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

Returns

Number of bytes sent.

nrfx_err_t nrfx_twis_rx_prepare(nrfx_twis_t const *p_instance, void *p_buf, size_t size)

Function for preparing the data for receiving.

This function must be used in response to the NRFX_TWIS_EVT_WRITE_REQ event.

Note

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

Parameters

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

  • p_buf – [in] Buffer that is to be filled with received data.

  • size – [in] Size of the buffer (maximum amount of data to receive).

Return values

  • NRFX_SUCCESS – The preparation finished properly.

  • NRFX_ERROR_INVALID_ADDR – The given p_buf is not placed inside the RAM.

  • NRFX_ERROR_INVALID_LENGTH – There is a wrong value in the size parameter.

  • NRFX_ERROR_INVALID_STATE – The module is not initialized or not enabled.

NRFX_STATIC_INLINE size_t nrfx_twis_rx_amount(nrfx_twis_t const *p_instance)

Function for getting the number of received bytes.

This function returns number of bytes received. It can be called after NRFX_TWIS_EVT_WRITE_DONE or NRFX_TWIS_EVT_WRITE_ERROR events.

Parameters

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

Returns

Number of bytes received.

bool nrfx_twis_is_busy(nrfx_twis_t const *p_instance)

Function for checking if the driver is busy right now.

This function tests the actual driver substate. If the driver is in any other state than IDLE or ERROR, this function returns true.

Parameters

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

Return values

  • true – The driver is in state other than ERROR or IDLE.

  • false – There is no transmission pending.

bool nrfx_twis_is_waiting_tx_buff(nrfx_twis_t const *p_instance)

Function for checking if the driver is waiting for a TX buffer.

If this function returns true, the driver is stalled expecting of the nrfx_twis_tx_prepare function call.

Parameters

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

Return values

  • true – The driver is waiting for nrfx_twis_tx_prepare.

  • false – The driver is not in the state where it is waiting for preparing a TX buffer.

bool nrfx_twis_is_waiting_rx_buff(nrfx_twis_t const *p_instance)

Function for checking if the driver is waiting for an RX buffer.

If this function returns true, the driver is stalled expecting of the nrfx_twis_rx_prepare function call.

Parameters

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

Return values

  • true – The driver is waiting for nrfx_twis_rx_prepare.

  • false – The driver is not in the state where it is waiting for preparing an RX buffer.

bool nrfx_twis_is_pending_tx(nrfx_twis_t const *p_instance)

Function for checking if the driver is sending data.

If this function returns true, there is an ongoing output transmission.

Parameters

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

Return values

  • true – There is an ongoing output transmission.

  • false – The driver is in other state.

bool nrfx_twis_is_pending_rx(nrfx_twis_t const *p_instance)

Function for checking if the driver is receiving data.

If this function returns true, there is an ongoing input transmission.

Parameters

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

Return values

  • true – There is an ongoing input transmission.

  • false – The driver is in other state.

struct nrfx_twis_t
#include <nrfx_twis.h>

TWIS driver instance data structure.

Public Members

NRF_TWIS_Type *p_reg

Pointer to a structure with TWIS registers.

uint8_t drv_inst_idx

Index of the driver instance. For internal use only.

struct nrfx_twis_evt_t
#include <nrfx_twis.h>

TWIS driver event structure.

Public Members

nrfx_twis_evt_type_t type

Event type.

bool buf_req

Flag for NRFX_TWIS_EVT_READ_REQ and NRFX_TWIS_EVT_WRITE_REQ.

Information if transmission buffer requires to be prepared.

uint32_t tx_amount

Data for NRFX_TWIS_EVT_READ_DONE.

uint32_t rx_amount

Data for NRFX_TWIS_EVT_WRITE_DONE.

uint32_t error

Data for NRFX_TWIS_EVT_GENERAL_ERROR.

union nrfx_twis_evt_t.[anonymous] data

Union to store event data.

struct nrfx_twis_config_t
#include <nrfx_twis.h>

Structure for TWIS configuration.

Public Members

uint32_t addr[2]

Set addresses that this slave should respond. Set 0 to disable.

uint32_t scl

SCL pin number.

uint32_t sda

SDA pin number.

nrf_gpio_pin_pull_t scl_pull

SCL pin pull.

nrf_gpio_pin_pull_t sda_pull

SDA pin pull.

uint8_t interrupt_priority

The priority of interrupt for the module to be set.

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.