TWIM driver¶
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group
nrfx_twim
Two Wire Interface Master with EasyDMA (TWIM) peripheral driver.
Defines
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NRFX_TWIM_INSTANCE
(id)¶ Macro for creating a TWI master driver instance.
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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.
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NRFX_TWIM_FLAG_TX_POSTINC
¶ Flag indicating that TX buffer address will be incremented after the transfer.
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NRFX_TWIM_FLAG_RX_POSTINC
¶ Flag indicating that RX buffer address will be incremented after the transfer.
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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.
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NRFX_TWIM_FLAG_HOLD_XFER
¶ Flag indicating that the transfer will be set up, but not started.
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NRFX_TWIM_FLAG_REPEATED_XFER
¶ Flag indicating that the transfer will be executed multiple times.
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NRFX_TWIM_FLAG_TX_NO_STOP
¶ Flag indicating that the TX transfer will not end with a stop condition.
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NRFX_TWIM_FLAG_NO_SPURIOUS_STOP_CHECK
¶ Flag indicating that checks for spurious STOP condition will not be performed.
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NRFX_TWIM_XFER_DESC_TX
(addr, p_data, length)¶ Macro for setting the TX transfer descriptor.
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NRFX_TWIM_XFER_DESC_RX
(addr, p_data, length)¶ Macro for setting the RX transfer descriptor.
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NRFX_TWIM_XFER_DESC_TXRX
(addr, p_tx, tx_len, p_rx, rx_len)¶ Macro for setting the TX-RX transfer descriptor.
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NRFX_TWIM_XFER_DESC_TXTX
(addr, p_tx, tx_len, p_tx2, tx_len2)¶ Macro for setting the TX-TX transfer descriptor.
Typedefs
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typedef void (*
nrfx_twim_evt_handler_t
)(nrfx_twim_evt_t const *p_event, void *p_context)¶ TWI event handler prototype.
Enums
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enum
nrfx_twim_evt_type_t
¶ TWI master driver event types.
Values:
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enumerator
NRFX_TWIM_EVT_DONE
¶ Transfer completed event.
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enumerator
NRFX_TWIM_EVT_ADDRESS_NACK
¶ Error event: NACK received after sending the address.
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enumerator
NRFX_TWIM_EVT_DATA_NACK
¶ Error event: NACK received after sending a data byte.
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enumerator
NRFX_TWIM_EVT_OVERRUN
¶ Error event: The unread data is replaced by new data.
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enumerator
NRFX_TWIM_EVT_BUS_ERROR
¶ Error event: An unexpected transition occurred on the bus.
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enumerator
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enum
nrfx_twim_xfer_type_t
¶ TWI master driver transfer types.
Values:
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enumerator
NRFX_TWIM_XFER_TX
¶ TX transfer.
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enumerator
NRFX_TWIM_XFER_RX
¶ RX transfer.
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enumerator
NRFX_TWIM_XFER_TXRX
¶ TX transfer followed by RX transfer with repeated start.
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enumerator
NRFX_TWIM_XFER_TXTX
¶ TX transfer followed by TX transfer with repeated start.
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enumerator
Functions
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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.
- Returns NRFX_SUCCESS
Initialization was successful.
- Returns NRFX_ERROR_INVALID_STATE
The driver is in invalid state.
- Returns NRFX_ERROR_INVALID_PARAM
Requested frequency is not available on the specified pins.
- Returns 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.
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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.
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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.
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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.
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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):
NRFX_TWIM_XFER_TXRX - Write operation followed by a read operation (without STOP condition in between).
NRFX_TWIM_XFER_TXTX - Write operation followed by a write operation (without STOP condition in between).
NRFX_TWIM_XFER_TX - Write operation (with or without STOP condition).
NRFX_TWIM_XFER_RX - Read operation (with STOP condition).
Additional options are provided using the flags parameter:
NRFX_TWIM_FLAG_TX_POSTINC and NRFX_TWIM_FLAG_RX_POSTINC - Post-incrementation of buffer addresses.
NRFX_TWIM_FLAG_NO_XFER_EVT_HANDLER - No user event handler after the transfer completion. In most cases, this also means no interrupt at the end of the transfer.
NRFX_TWIM_FLAG_HOLD_XFER - Driver is not starting the transfer. Use this flag if the transfer is triggered externally by PPI. Use nrfx_twim_start_task_get to get the address of the start task.
NRFX_TWIM_FLAG_REPEATED_XFER - Prepare for repeated transfers. You can set up a number of transfers that will be triggered externally (for example by PPI). An example is a TXRX transfer with the options NRFX_TWIM_FLAG_RX_POSTINC, NRFX_TWIM_FLAG_NO_XFER_EVT_HANDLER, and NRFX_TWIM_FLAG_REPEATED_XFER. After the transfer is set up, a set of transfers can be triggered by PPI that will read, for example, the same register of an external component and put it into a RAM buffer without any interrupts. nrfx_twim_stopped_event_get can be used to get the address of the STOPPED event, which can be used to count the number of transfers. If NRFX_TWIM_FLAG_REPEATED_XFER is used, the driver does not set the driver instance into busy state, so you must ensure that the next transfers are set up when TWIM is not active.
NRFX_TWIM_FLAG_TX_NO_STOP - No stop condition after the TX transfer.
NRFX_TWIM_FLAG_NO_SPURIOUS_STOP_CHECK - Checks for spurious STOP conditions are disabled. Used together with NRFX_TWIM_FLAG_NO_XFER_EVT_HANDLER can result in lower power consumption when transfers are triggered externally and CPU is sleeping. Use only with I2C standard-compliant slave devices.
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
Some flag combinations are invalid:
NRFX_TWIM_FLAG_TX_NO_STOP with nrfx_twim_xfer_desc_t::type different than NRFX_TWIM_XFER_TX
NRFX_TWIM_FLAG_REPEATED_XFER with nrfx_twim_xfer_desc_t::type set to NRFX_TWIM_XFER_TXTX
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).
- Returns NRFX_SUCCESS
The procedure is successful.
- Returns NRFX_ERROR_BUSY
The driver is not ready for a new transfer.
- Returns NRFX_ERROR_NOT_SUPPORTED
The provided parameters are not supported.
- Returns NRFX_ERROR_INTERNAL
An unexpected transition occurred on the bus.
- Returns NRFX_ERROR_INVALID_ADDR
The provided buffers are not placed in the Data RAM region.
- Returns NRFX_ERROR_DRV_TWI_ERR_OVERRUN
The unread data is replaced by new data.
- Returns NRFX_ERROR_DRV_TWI_ERR_ANACK
NACK is received after sending the address.
- Returns NRFX_ERROR_DRV_TWI_ERR_DNACK
NACK is received after sending a data byte.
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bool
nrfx_twim_is_busy
(nrfx_twim_t const *p_instance)¶ Function for checking the TWI driver state.
- Parameters
p_instance – [in] TWI instance.
- Returns true
The TWI driver is currently busy performing a transfer.
- Returns false
The TWI driver is ready for a new transfer.
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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.
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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.
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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.
- Returns NRFX_SUCCESS
Bus recovery was successful.
- Returns NRFX_ERROR_INTERNAL
Bus recovery failed.
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struct
nrfx_twim_t
¶ - #include <nrfx_twim.h>
Structure for the TWI master driver instance.
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struct
nrfx_twim_config_t
¶ - #include <nrfx_twim.h>
Structure for the TWI master driver instance configuration.
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struct
nrfx_twim_xfer_desc_t
¶ - #include <nrfx_twim.h>
Structure for a TWI transfer descriptor.
Public Members
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nrfx_twim_xfer_type_t
type
¶ Type of transfer.
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uint8_t
address
¶ Slave address.
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size_t
primary_length
¶ Number of bytes transferred.
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size_t
secondary_length
¶ Number of bytes transferred.
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uint8_t *
p_primary_buf
¶ Pointer to transferred data.
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uint8_t *
p_secondary_buf
¶ Pointer to transferred data.
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nrfx_twim_xfer_type_t
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struct
nrfx_twim_evt_t
¶ - #include <nrfx_twim.h>
Structure for a TWI event.
Public Members
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nrfx_twim_evt_type_t
type
¶ Event type.
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nrfx_twim_xfer_desc_t
xfer_desc
¶ Transfer details.
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nrfx_twim_evt_type_t
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