LEUART - Low Energy UART#

Low Energy Universal Asynchronous Receiver/Transmitter (LEUART) Peripheral API.

This module contains functions to control the LEUART peripheral of Silicon Labs 32-bit MCUs and SoCs. The LEUART module provides the full UART communication using a low frequency 32.768 kHz clock and has special features for communication without the CPU intervention.

Modules#

LEUART_Init_TypeDef

Enumerations#

enum

LEUART_Databits_TypeDef {

leuartDatabits8 = LEUART_CTRL_DATABITS_EIGHT

leuartDatabits9 = LEUART_CTRL_DATABITS_NINE

}

Data bit selection.

enum

LEUART_Enable_TypeDef {

leuartDisable = 0x0

leuartEnableRx = LEUART_CMD_RXEN

leuartEnableTx = LEUART_CMD_TXEN

leuartEnable = (LEUART_CMD_RXEN | LEUART_CMD_TXEN)

}

Enable selection.

enum

LEUART_Parity_TypeDef {

leuartNoParity = LEUART_CTRL_PARITY_NONE

leuartEvenParity = LEUART_CTRL_PARITY_EVEN

leuartOddParity = LEUART_CTRL_PARITY_ODD

}

Parity selection.

enum

LEUART_Stopbits_TypeDef {

leuartStopbits1 = LEUART_CTRL_STOPBITS_ONE

leuartStopbits2 = LEUART_CTRL_STOPBITS_TWO

}

Stop bits selection.

Functions#

uint32_t

LEUART_BaudrateCalc(uint32_t refFreq, uint32_t clkdiv)

Calculate the baudrate for the LEUART given reference frequency and clock division.

uint32_t

LEUART_BaudrateGet(LEUART_TypeDef *leuart)

Get the current baudrate for LEUART.

void

LEUART_BaudrateSet(LEUART_TypeDef *leuart, uint32_t refFreq, uint32_t baudrate)

Configure the baudrate (or as close as possible to a specified baudrate).

void

LEUART_Enable(LEUART_TypeDef *leuart, LEUART_Enable_TypeDef enable)

Enable/disable the LEUART receiver and/or transmitter.

void

LEUART_FreezeEnable(LEUART_TypeDef *leuart, bool enable)

LEUART register synchronization freeze control.

void

LEUART_Init(LEUART_TypeDef *leuart, LEUART_Init_TypeDef const *init)

Initialize LEUART.

void

LEUART_Reset(LEUART_TypeDef *leuart)

Reset LEUART to the same state that it was in after a hardware reset.

uint8_t

LEUART_Rx(LEUART_TypeDef *leuart)

Receive one 8 bit frame, (or part of 9 bit frame).

uint16_t

LEUART_RxExt(LEUART_TypeDef *leuart)

Receive one 8-9 bit frame with extended information.

void

LEUART_Tx(LEUART_TypeDef *leuart, uint8_t data)

Transmit one frame.

void

LEUART_TxExt(LEUART_TypeDef *leuart, uint16_t data)

Transmit one 8-9 bit frame with extended control.

void

LEUART_TxDmaInEM2Enable(LEUART_TypeDef *leuart, bool enable)

Enables handling of LEUART TX by DMA in EM2.

void

LEUART_RxDmaInEM2Enable(LEUART_TypeDef *leuart, bool enable)

Enables handling of LEUART RX by DMA in EM2.

void

LEUART_IntClear(LEUART_TypeDef *leuart, uint32_t flags)

Clear one or more pending LEUART interrupts.

void

LEUART_IntDisable(LEUART_TypeDef *leuart, uint32_t flags)

Disable one or more LEUART interrupts.

void

LEUART_IntEnable(LEUART_TypeDef *leuart, uint32_t flags)

Enable one or more LEUART interrupts.

uint32_t

LEUART_IntGet(LEUART_TypeDef *leuart)

Get pending LEUART interrupt flags.

uint32_t

LEUART_IntGetEnabled(LEUART_TypeDef *leuart)

Get enabled and pending LEUART interrupt flags.

void

LEUART_IntSet(LEUART_TypeDef *leuart, uint32_t flags)

Set one or more pending LEUART interrupts from SW.

uint32_t

LEUART_StatusGet(LEUART_TypeDef *leuart)

Get LEUART STATUS register.

uint8_t

LEUART_RxDataGet(LEUART_TypeDef *leuart)

Receive one 8 bit frame, (or part of a 9 bit frame).

uint16_t

LEUART_RxDataXGet(LEUART_TypeDef *leuart)

Receive one 8-9 bit frame, with extended information.

Macros#

#define

LEUART_INIT_DEFAULT undefined

Default configuration for LEUART initialization structure.

Enumeration Documentation#

LEUART_Databits_TypeDef#

LEUART_Databits_TypeDef

Data bit selection.

Enumerator
leuartDatabits8	8 data bits.
leuartDatabits9	9 data bits.

LEUART_Enable_TypeDef#

LEUART_Enable_TypeDef

Enable selection.

Enumerator
leuartDisable	Disable both receiver and transmitter.
leuartEnableRx	Enable receiver only, transmitter disabled.
leuartEnableTx	Enable transmitter only, receiver disabled.
leuartEnable	Enable both receiver and transmitter.

LEUART_Parity_TypeDef#

LEUART_Parity_TypeDef

Parity selection.

Enumerator
leuartNoParity	No parity.
leuartEvenParity	Even parity.
leuartOddParity	Odd parity.

LEUART_Stopbits_TypeDef#

LEUART_Stopbits_TypeDef

Stop bits selection.

Enumerator
leuartStopbits1	1 stop bits.
leuartStopbits2	2 stop bits.

Function Documentation#

LEUART_BaudrateCalc#

uint32_t LEUART_BaudrateCalc (uint32_t refFreq, uint32_t clkdiv)

Calculate the baudrate for the LEUART given reference frequency and clock division.

Parameters

Type	Direction	Argument Name	Description
uint32_t	[in]	refFreq	The LEUART peripheral frequency used.
uint32_t	[in]	clkdiv	The clock division factor to be used.

This function returns the baudrate that a LEUART module will use if configured with the given frequency and clock divisor. Notice that this function will not use the hardware configuration. It can be used to determine if a given configuration is sufficiently accurate for the application.

Returns

A baudrate with given settings.

LEUART_BaudrateGet#

uint32_t LEUART_BaudrateGet (LEUART_TypeDef * leuart)

Get the current baudrate for LEUART.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.

This function returns the actual baudrate (not considering the oscillator inaccuracies) used by the LEUART peripheral.

Returns

The current baudrate.

LEUART_BaudrateSet#

void LEUART_BaudrateSet (LEUART_TypeDef * leuart, uint32_t refFreq, uint32_t baudrate)

Configure the baudrate (or as close as possible to a specified baudrate).

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
uint32_t	[in]	refFreq	The LEUART reference clock frequency in Hz that will be used. If set to 0, the currently configured reference clock is assumed.
uint32_t	[in]	baudrate	A baudrate to try to achieve for LEUART.

Note

The baudrate setting requires synchronization into the low-frequency domain. If the same register is modified before a previous update has completed, this function will stall until the previous synchronization has completed.

LEUART_Enable#

void LEUART_Enable (LEUART_TypeDef * leuart, LEUART_Enable_TypeDef enable)

Enable/disable the LEUART receiver and/or transmitter.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
LEUART_Enable_TypeDef	[in]	enable	Select status for receiver/transmitter.

Notice that this function does not do any configuration. Enabling should normally be done after the initialization is done (if not enabled as part of initialization).

Note

Enabling/disabling requires synchronization into the low-frequency domain. If the same register is modified before a previous update has completed, this function will stall until the previous synchronization has completed.

LEUART_FreezeEnable#

void LEUART_FreezeEnable (LEUART_TypeDef * leuart, bool enable)

LEUART register synchronization freeze control.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
bool	[in]	enable	True - enable freeze, modified registers are not propagated to the LF domain False - disables freeze, modified registers are propagated to the LF domain

Some LEUART registers require synchronization into the low-frequency (LF) domain. The freeze feature allows for several such registers to be modified before passing them to the LF domain simultaneously (which takes place when the freeze mode is disabled).

Note

When enabling freeze mode, this function will wait for all current ongoing LEUART synchronization to the LF domain to complete (Normally synchronization will not be in progress.) However, for this reason, when using freeze mode, modifications of registers requiring LF synchronization should be done within one freeze enable/disable block to avoid unnecessary stalling.

LEUART_Init#

void LEUART_Init (LEUART_TypeDef * leuart, LEUART_Init_TypeDef const * init)

Initialize LEUART.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
LEUART_Init_TypeDef const *	[in]	init	A pointer to the initialization structure used to configure basic async setup.

This function will configure basic settings to operate in normal asynchronous mode. Consider using LEUART_Reset() prior to this function if the state of configuration is not known, since only configuration settings specified by init are set.

Special control setup not covered by this function may be done either before or after using this function (but normally before enabling) by direct modification of the CTRL register.

Notice that pins used by the LEUART module must be properly configured by the user explicitly for the LEUART to work as intended. (When configuring pins consider the sequence of configuration to avoid unintended pulses/glitches on output pins.)

Note

Initializing requires synchronization into the low-frequency domain. If the same register is modified before a previous update has completed, this function will stall until the previous synchronization has completed.

LEUART_Reset#

void LEUART_Reset (LEUART_TypeDef * leuart)

Reset LEUART to the same state that it was in after a hardware reset.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.

LEUART_Rx#

uint8_t LEUART_Rx (LEUART_TypeDef * leuart)

Receive one 8 bit frame, (or part of 9 bit frame).

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.

This function is normally used to receive one frame when operating with frame length 8 bits. See LEUART_RxExt() for reception of 9 bit frames.

Notice that possible parity/stop bits are not considered a part of the specified frame bit length.

Note

This function will stall if the buffer is empty until data is received.

Returns

Data received.

LEUART_RxExt#

uint16_t LEUART_RxExt (LEUART_TypeDef * leuart)

Receive one 8-9 bit frame with extended information.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.

This function is normally used to receive one frame and additional RX status information is required.

Note

This function will stall if buffer is empty until data is received.

Returns

Data received.

LEUART_Tx#

void LEUART_Tx (LEUART_TypeDef * leuart, uint8_t data)

Transmit one frame.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
uint8_t	[in]	data	Data to transmit. See details above for more info.

Depending on the frame length configuration, 8 (least significant) bits from data are transmitted. If the frame length is 9, 8 bits are transmitted from data and one bit as specified by the CTRL register, BIT8DV field. See LEUART_TxExt() for transmitting 9 bit frame with full control of all 9 bits.

Notice that possible parity/stop bits in asynchronous mode are not considered a part of the specified frame bit length.

Note

This function will stall if buffer is full until the buffer becomes available.

LEUART_TxExt#

void LEUART_TxExt (LEUART_TypeDef * leuart, uint16_t data)

Transmit one 8-9 bit frame with extended control.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
uint16_t	[in]	data	Data to transmit with extended control. Least significant bit contains frame bits and additional control bits are available as documented in the reference manual (set to 0 if not used).

Notice that possible parity/stop bits in asynchronous mode are not considered a part of the specified frame bit length.

Note

This function will stall if the buffer is full until the buffer becomes available.

LEUART_TxDmaInEM2Enable#

void LEUART_TxDmaInEM2Enable (LEUART_TypeDef * leuart, bool enable)

Enables handling of LEUART TX by DMA in EM2.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
bool	[in]	enable	True - enables functionality False - disables functionality

LEUART_RxDmaInEM2Enable#

void LEUART_RxDmaInEM2Enable (LEUART_TypeDef * leuart, bool enable)

Enables handling of LEUART RX by DMA in EM2.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	A pointer to the LEUART peripheral register block.
bool	[in]	enable	True - enables functionality False - disables functionality

LEUART_IntClear#

void LEUART_IntClear (LEUART_TypeDef * leuart, uint32_t flags)

Clear one or more pending LEUART interrupts.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.
uint32_t	[in]	flags	Pending LEUART interrupt source to clear. Use a bitwise logic OR combination of valid interrupt flags for LEUART module (LEUART_IF_nnn).

LEUART_IntDisable#

void LEUART_IntDisable (LEUART_TypeDef * leuart, uint32_t flags)

Disable one or more LEUART interrupts.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.
uint32_t	[in]	flags	LEUART interrupt sources to disable. Use a bitwise logic OR combination of valid interrupt flags for LEUART module (LEUART_IF_nnn).

LEUART_IntEnable#

void LEUART_IntEnable (LEUART_TypeDef * leuart, uint32_t flags)

Enable one or more LEUART interrupts.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.
uint32_t	[in]	flags	LEUART interrupt sources to enable. Use a bitwise logic OR combination of valid interrupt flags for LEUART module (LEUART_IF_nnn).

Note

Depending on the use, a pending interrupt may already be set prior to enabling the interrupt. To ignore a pending interrupt, consider using LEUART_IntClear() prior to enabling the interrupt.

LEUART_IntGet#

uint32_t LEUART_IntGet (LEUART_TypeDef * leuart)

Get pending LEUART interrupt flags.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.

Note

The event bits are not cleared by the use of this function.

Returns

LEUART interrupt sources pending. A bitwise logic OR combination of valid interrupt flags for LEUART module (LEUART_IF_nnn).

LEUART_IntGetEnabled#

uint32_t LEUART_IntGetEnabled (LEUART_TypeDef * leuart)

Get enabled and pending LEUART interrupt flags.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.

Useful for handling more interrupt sources in the same interrupt handler.

Note

Interrupt flags are not cleared by the use of this function.

Returns

Pending and enabled LEUART interrupt sources. The return value is the bitwise AND combination of
- the OR combination of enabled interrupt sources in LEUARTx_IEN_nnn register (LEUARTx_IEN_nnn) and
- the OR combination of valid interrupt flags of LEUART module (LEUARTx_IF_nnn).

LEUART_IntSet#

void LEUART_IntSet (LEUART_TypeDef * leuart, uint32_t flags)

Set one or more pending LEUART interrupts from SW.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.
uint32_t	[in]	flags	LEUART interrupt sources to set to pending. Use a bitwise logic OR combination of valid interrupt flags for LEUART module (LEUART_IF_nnn).

LEUART_StatusGet#

uint32_t LEUART_StatusGet (LEUART_TypeDef * leuart)

Get LEUART STATUS register.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.

Returns

STATUS register value.

LEUART_RxDataGet#

uint8_t LEUART_RxDataGet (LEUART_TypeDef * leuart)

Receive one 8 bit frame, (or part of a 9 bit frame).

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.

Used to quickly receive one 8 bit frame by reading RXDATA register directly, without checking STATUS register for RXDATAV flag. This can be useful from RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read received data. Please refer to LEUART_RxDataXGet() for reception of 9 bit frames.

Note

Since this function does not check if the RXDATA register actually holds valid data, it should only be used in situations when it is certain that there is valid data, ensured by some external program routine, e.g., when handling an RXDATAV interrupt. The LEUART_Rx() is normally a better choice if the validity of the RXDATA register is not certain.
Notice that possible parity/stop bits are not considered part of specified frame bit length.

Returns

Data received.

LEUART_RxDataXGet#

uint16_t LEUART_RxDataXGet (LEUART_TypeDef * leuart)

Receive one 8-9 bit frame, with extended information.

Parameters

Type	Direction	Argument Name	Description
LEUART_TypeDef *	[in]	leuart	Pointer to LEUART peripheral register block.

Used to quickly receive one 8-9 bit frame with extended information by reading RXDATAX register directly, without checking STATUS register for RXDATAV flag. This can be useful from RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read received data.

Note

Since this function does not check if the RXDATAX register actually holds valid data, it should only be used in situations when it is certain that there is valid data, ensured by some external program routine, e.g., when handling an RXDATAV interrupt. The LEUART_RxExt() is normally a better choice if the validity of the RXDATAX register is not certain.
Notice that possible parity/stop bits are not considered part of specified frame bit length.

Returns

Data received.