USART - Synchronous/Asynchronous Serial

Description

Universal Synchronous/Asynchronous Receiver/Transmitter Peripheral API.

The Universal Synchronous/Asynchronous Receiver/Transmitter (USART) is a very flexible serial I/O module. It supports full duplex asynchronous UART communication as well as RS-485, SPI, MicroWire, and 3-wire. It can also interface with ISO7816 Smart-Cards, and IrDA devices.

The USART has a wide selection of operating modes, frame formats, and baud rates. All features are supported through the API of this module.

Triple buffering and DMA support makes high data-rates possible with minimal CPU intervention. It is possible to transmit and receive large frames while the MCU remains in EM1 Sleep.

This module does not support DMA configuration. The UARTDRV and SPIDRV drivers provide full support for DMA and more.

The following steps are necessary for basic operation:

Clock enable:

#if !defined(_SILICON_LABS_32B_SERIES_2)
/* USART is a HFPERCLK peripheral. Enable HFPERCLK domain and USART0.
* We also need to enable the clock for GPIO to configure pins. */
CMU_ClockEnable (cmuClock_HFPER, true );
CMU_ClockEnable (cmuClock_USART0, true );
CMU_ClockEnable (cmuClock_GPIO, true );
#endif

To initialize the USART for asynchronous operation (e.g., UART):

/* Initialize with default settings and then update fields according to application requirements. */
USART_InitAsync_TypeDef initAsync = USART_INITASYNC_DEFAULT ;
initAsync. baudrate = 38400;
USART_InitAsync (USART0, &initAsync);

To initialize the USART for synchronous operation (e.g., SPI):

/* Initialize with default settings and then update fields according to application requirements. */
USART_InitSync_TypeDef initSync = USART_INITSYNC_DEFAULT ;
/* Operate as SPI master */
initSync. master = true ;
/* Clock idle low, sample on falling edge. */
initSync. clockMode = usartClockMode1 ;
USART_InitSync (USART0, &initSync);

After pins are assigned for the application/board, enable pins at the desired location. Available locations can be obtained from the Pin Definitions section in the data sheet.

Note
UARTDRV supports all types of UART flow control. Software assisted hardware flow control is available for parts without true UART hardware flow control.

Data Structures

struct USART_InitAsync_TypeDef
Asynchronous mode initialization structure.
struct USART_PrsTriggerInit_TypeDef
USART PRS trigger enable.
struct USART_InitSync_TypeDef
Synchronous mode initialization structure.
struct USART_InitIrDA_TypeDef
IrDA mode initialization structure.
struct USART_InitI2s_TypeDef
I2S mode initialization structure.

Functions

void USART_BaudrateAsyncSet (USART_TypeDef *usart, uint32_t refFreq, uint32_t baudrate, USART_OVS_TypeDef ovs)
Configure USART/UART operating in asynchronous mode to use a given baudrate (or as close as possible to a specified baudrate).
uint32_t USART_BaudrateCalc (uint32_t refFreq, uint32_t clkdiv, bool syncmode, USART_OVS_TypeDef ovs)
Calculate baudrate for USART/UART given reference frequency, clock division, and oversampling rate (if async mode).
uint32_t USART_BaudrateGet (USART_TypeDef *usart)
Get the current baudrate for USART/UART.
void USART_BaudrateSyncSet (USART_TypeDef *usart, uint32_t refFreq, uint32_t baudrate)
Configure the USART operating in synchronous mode to use a given baudrate (or as close as possible to a specified baudrate).
void USART_Enable (USART_TypeDef *usart, USART_Enable_TypeDef enable)
Enable/disable USART/UART receiver and/or transmitter.
void USART_InitAsync (USART_TypeDef *usart, const USART_InitAsync_TypeDef *init)
Initialize USART/UART for normal asynchronous mode.
void USART_InitSync (USART_TypeDef *usart, const USART_InitSync_TypeDef *init)
Initialize USART for synchronous mode.
void USARTn_InitIrDA (USART_TypeDef *usart, const USART_InitIrDA_TypeDef *init)
Initialize USART for asynchronous IrDA mode.
void USART_InitI2s (USART_TypeDef *usart, USART_InitI2s_TypeDef *init)
Initialize USART for I2S mode.
void USART_InitPrsTrigger (USART_TypeDef *usart, const USART_PrsTriggerInit_TypeDef *init)
Initialize the automatic transmissions using PRS channel as a trigger.
void USART_IntClear (USART_TypeDef *usart, uint32_t flags)
Clear one or more pending USART interrupts.
void USART_IntDisable (USART_TypeDef *usart, uint32_t flags)
Disable one or more USART interrupts.
void USART_IntEnable (USART_TypeDef *usart, uint32_t flags)
Enable one or more USART interrupts.
uint32_t USART_IntGet (USART_TypeDef *usart)
Get pending USART interrupt flags.
uint32_t USART_IntGetEnabled (USART_TypeDef *usart)
Get enabled and pending USART interrupt flags.
void USART_IntSet (USART_TypeDef *usart, uint32_t flags)
Set one or more pending USART interrupts from SW.
uint32_t USART_StatusGet (USART_TypeDef *usart)
Get USART STATUS register.
void USART_Reset (USART_TypeDef *usart)
Reset USART/UART to the same state that it was in after a hardware reset.
uint8_t USART_Rx (USART_TypeDef *usart)
Receive one 4-8 bit frame, (or part of 10-16 bit frame).
uint16_t USART_RxDouble (USART_TypeDef *usart)
Receive two 4-8 bit frames or one 10-16 bit frame.
uint32_t USART_RxDoubleExt (USART_TypeDef *usart)
Receive two 4-9 bit frames, or one 10-16 bit frame with extended information.
uint16_t USART_RxExt (USART_TypeDef *usart)
Receive one 4-9 bit frame (or part of 10-16 bit frame) with extended information.
uint8_t USART_RxDataGet (USART_TypeDef *usart)
Receive one 4-8 bit frame, (or part of 10-16 bit frame).
uint16_t USART_RxDoubleGet (USART_TypeDef *usart)
Receive two 4-8 bit frames, or one 10-16 bit frame.
uint32_t USART_RxDoubleXGet (USART_TypeDef *usart)
Receive two 4-9 bit frames, or one 10-16 bit frame with extended information.
uint16_t USART_RxDataXGet (USART_TypeDef *usart)
Receive one 4-9 bit frame, (or part of 10-16 bit frame) with extended information.
uint8_t USART_SpiTransfer (USART_TypeDef *usart, uint8_t data)
Perform one 8 bit frame SPI transfer.
void USART_Tx (USART_TypeDef *usart, uint8_t data)
Transmit one 4-9 bit frame.
void USART_TxDouble (USART_TypeDef *usart, uint16_t data)
Transmit two 4-9 bit frames or one 10-16 bit frame.
void USART_TxDoubleExt (USART_TypeDef *usart, uint32_t data)
Transmit two 4-9 bit frames or one 10-16 bit frame with extended control.
void USART_TxExt (USART_TypeDef *usart, uint16_t data)
Transmit one 4-9 bit frame with extended control.

Macros

#define USART_INITASYNC_DEFAULT
Default configuration for USART asynchronous initialization structure.
#define USART_INITPRSTRIGGER_DEFAULT
Default configuration for USART PRS triggering structure.
#define USART_INITSYNC_DEFAULT
Default configuration for USART sync initialization structure.
#define USART_INITIRDA_DEFAULT
Default configuration for IrDA mode initialization structure.
#define USART_INITI2S_DEFAULT
Default configuration for I2S mode initialization structure.

Typedefs

typedef uint8_t USART_PRS_Channel_t
PRS Channel type.

Enumerations

enum USART_Databits_TypeDef {
usartDatabits4 = USART_FRAME_DATABITS_FOUR,
usartDatabits5 = USART_FRAME_DATABITS_FIVE,
usartDatabits6 = USART_FRAME_DATABITS_SIX,
usartDatabits7 = USART_FRAME_DATABITS_SEVEN,
usartDatabits8 = USART_FRAME_DATABITS_EIGHT,
usartDatabits9 = USART_FRAME_DATABITS_NINE,
usartDatabits10 = USART_FRAME_DATABITS_TEN,
usartDatabits11 = USART_FRAME_DATABITS_ELEVEN,
usartDatabits12 = USART_FRAME_DATABITS_TWELVE,
usartDatabits13 = USART_FRAME_DATABITS_THIRTEEN,
usartDatabits14 = USART_FRAME_DATABITS_FOURTEEN,
usartDatabits15 = USART_FRAME_DATABITS_FIFTEEN,
usartDatabits16 = USART_FRAME_DATABITS_SIXTEEN
}
Databit selection.
enum USART_Enable_TypeDef {
usartDisable = 0x0,
usartEnableRx = USART_CMD_RXEN,
usartEnableTx = USART_CMD_TXEN,
usartEnable = (USART_CMD_RXEN | USART_CMD_TXEN)
}
Enable selection.
enum USART_OVS_TypeDef {
usartOVS16 = USART_CTRL_OVS_X16,
usartOVS8 = USART_CTRL_OVS_X8,
usartOVS6 = USART_CTRL_OVS_X6,
usartOVS4 = USART_CTRL_OVS_X4
}
Oversampling selection, used for asynchronous operation.
enum USART_Parity_TypeDef {
usartNoParity = USART_FRAME_PARITY_NONE,
usartEvenParity = USART_FRAME_PARITY_EVEN,
usartOddParity = USART_FRAME_PARITY_ODD
}
Parity selection, mainly used for asynchronous operation.
enum USART_Stopbits_TypeDef {
usartStopbits0p5 = USART_FRAME_STOPBITS_HALF,
usartStopbits1 = USART_FRAME_STOPBITS_ONE,
usartStopbits1p5 = USART_FRAME_STOPBITS_ONEANDAHALF,
usartStopbits2 = USART_FRAME_STOPBITS_TWO
}
Stop bits selection, used for asynchronous operation.
enum USART_HwFlowControl_TypeDef {
usartHwFlowControlNone = 0,
usartHwFlowControlCts ,
usartHwFlowControlRts ,
usartHwFlowControlCtsAndRts
}
Hardware Flow Control Selection.
enum USART_ClockMode_TypeDef {
usartClockMode0 = USART_CTRL_CLKPOL_IDLELOW | USART_CTRL_CLKPHA_SAMPLELEADING,
usartClockMode1 = USART_CTRL_CLKPOL_IDLELOW | USART_CTRL_CLKPHA_SAMPLETRAILING,
usartClockMode2 = USART_CTRL_CLKPOL_IDLEHIGH | USART_CTRL_CLKPHA_SAMPLELEADING,
usartClockMode3 = USART_CTRL_CLKPOL_IDLEHIGH | USART_CTRL_CLKPHA_SAMPLETRAILING
}
Clock polarity/phase mode.
enum USART_IrDAPw_Typedef {
usartIrDAPwONE = USART_IRCTRL_IRPW_ONE,
usartIrDAPwTWO = USART_IRCTRL_IRPW_TWO,
usartIrDAPwTHREE = USART_IRCTRL_IRPW_THREE,
usartIrDAPwFOUR = USART_IRCTRL_IRPW_FOUR
}
Pulse width selection for IrDA mode.
enum USART_I2sFormat_TypeDef {
usartI2sFormatW32D32 = USART_I2SCTRL_FORMAT_W32D32,
usartI2sFormatW32D24M = USART_I2SCTRL_FORMAT_W32D24M,
usartI2sFormatW32D24 = USART_I2SCTRL_FORMAT_W32D24,
usartI2sFormatW32D16 = USART_I2SCTRL_FORMAT_W32D16,
usartI2sFormatW32D8 = USART_I2SCTRL_FORMAT_W32D8,
usartI2sFormatW16D16 = USART_I2SCTRL_FORMAT_W16D16,
usartI2sFormatW16D8 = USART_I2SCTRL_FORMAT_W16D8,
usartI2sFormatW8D8 = USART_I2SCTRL_FORMAT_W8D8
}
I2S format selection.
enum USART_I2sJustify_TypeDef {
usartI2sJustifyLeft = USART_I2SCTRL_JUSTIFY_LEFT,
usartI2sJustifyRight = USART_I2SCTRL_JUSTIFY_RIGHT
}
I2S frame data justify.

Function Documentation

◆ USART_BaudrateAsyncSet()

void USART_BaudrateAsyncSet ( USART_TypeDef * usart,
uint32_t refFreq,
uint32_t baudrate,
USART_OVS_TypeDef ovs
)

Configure USART/UART operating in asynchronous mode to use a given baudrate (or as close as possible to a specified baudrate).

Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] refFreq USART/UART reference clock frequency in Hz. If set to 0, the currently configured reference clock is assumed.
[in] baudrate Baudrate to try to achieve for USART/UART.
[in] ovs Oversampling to be used. Normal is 16x oversampling but lower oversampling may be used to achieve higher rates or better baudrate accuracy in some cases. Notice that lower oversampling frequency makes the channel more vulnerable to bit faults during reception due to clock inaccuracies compared to the link partner.

◆ USART_BaudrateCalc()

uint32_t USART_BaudrateCalc ( uint32_t refFreq,
uint32_t clkdiv,
bool syncmode,
USART_OVS_TypeDef ovs
)

Calculate baudrate for USART/UART given reference frequency, clock division, and oversampling rate (if async mode).

This function returns the baudrate that a USART/UART module will use if configured with the given frequency, clock divisor, and mode. 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.

Parameters
[in] refFreq USART/UART HF peripheral frequency used.
[in] clkdiv A clock division factor to be used.
[in] syncmode
  • True - synchronous mode operation.
  • False - asynchronous mode operation.
[in] ovs Oversampling used if in asynchronous mode. Not used if syncmode is true.
Returns
Baudrate with given settings.

◆ USART_BaudrateGet()

uint32_t USART_BaudrateGet ( USART_TypeDef * usart )

Get the current baudrate for USART/UART.

This function returns the actual baudrate (not considering oscillator inaccuracies) used by a USART/UART peripheral.

Parameters
[in] usart A pointer to the USART/UART peripheral register block.
Returns
The current baudrate.

◆ USART_BaudrateSyncSet()

void USART_BaudrateSyncSet ( USART_TypeDef * usart,
uint32_t refFreq,
uint32_t baudrate
)

Configure the USART operating in synchronous mode to use a given baudrate (or as close as possible to a specified baudrate).

The configuration will be set to use a baudrate <= the specified baudrate to ensure that the baudrate does not exceed the specified value.

The fractional clock division is suppressed, although the hardware design allows it. It could cause half clock cycles to exceed a specified limit and thus potentially violate specifications for the slave device. In some special situations, a fractional clock division may be useful even in synchronous mode, but in those cases it must be directly adjusted, possibly assisted by USART_BaudrateCalc() :

Parameters
[in] usart A pointer to the USART peripheral register block. (Cannot be used on UART modules.)
[in] refFreq A USART reference clock frequency in Hz that will be used. If set to 0, the currently-configured reference clock is assumed.
[in] baudrate Baudrate to try to achieve for USART.

◆ USART_Enable()

void USART_Enable ( USART_TypeDef * usart,
USART_Enable_TypeDef enable
)

Enable/disable USART/UART receiver and/or transmitter.

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

Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] enable Select the status for the receiver/transmitter.

◆ USART_InitAsync()

void USART_InitAsync ( USART_TypeDef * usart,
const USART_InitAsync_TypeDef * init
)

Initialize USART/UART for normal asynchronous mode.

This function will configure basic settings to operate in normal asynchronous mode.

A special control setup not covered by this function must be done after using this function by direct modification of the CTRL register.

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

Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] init A pointer to the initialization structure used to configure the basic async setup.

◆ USART_InitSync()

void USART_InitSync ( USART_TypeDef * usart,
const USART_InitSync_TypeDef * init
)

Initialize USART for synchronous mode.

This function will configure basic settings to operate in synchronous mode.

A special control setup not covered by this function must be done after using this function by direct modification of the CTRL register.

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

Parameters
[in] usart A pointer to the USART peripheral register block. (UART does not support this mode.)
[in] init A pointer to the initialization structure used to configure basic async setup.

◆ USARTn_InitIrDA()

void USARTn_InitIrDA ( USART_TypeDef * usart,
const USART_InitIrDA_TypeDef * init
)

Initialize USART for asynchronous IrDA mode.

This function will configure basic settings to operate in asynchronous IrDA mode.

A special control setup not covered by this function must be done after using this function by direct modification of the CTRL and IRCTRL registers.

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

Parameters
[in] usart A pointer to the USART peripheral register block.
[in] init A pointer to the initialization structure used to configure async IrDA setup.
Note
Not all USART instances support IrDA. See the data sheet for your device.

◆ USART_InitI2s()

void USART_InitI2s ( USART_TypeDef * usart,
USART_InitI2s_TypeDef * init
)

Initialize USART for I2S mode.

This function will configure basic settings to operate in I2S mode.

A special control setup not covered by this function must be done after using this function by direct modification of the CTRL and I2SCTRL registers.

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

Parameters
[in] usart A pointer to the USART peripheral register block. (UART does not support this mode.)
[in] init A pointer to the initialization structure used to configure the basic I2S setup.
Note
This function does not apply to all USART's. See the chip Reference Manual.

◆ USART_InitPrsTrigger()

void USART_InitPrsTrigger ( USART_TypeDef * usart,
const USART_PrsTriggerInit_TypeDef * init
)

Initialize the automatic transmissions using PRS channel as a trigger.

Note
Initialize USART with USART_Init() before setting up the PRS configuration.
Parameters
[in] usart A pointer to USART to configure.
[in] init A pointer to the initialization structure.

◆ USART_IntClear()

void USART_IntClear ( USART_TypeDef * usart,
uint32_t flags
)
inline

Clear one or more pending USART interrupts.

Parameters
[in] usart Pointer to USART/UART peripheral register block.
[in] flags Pending USART/UART interrupt source(s) to clear. Use one or more valid interrupt flags for the USART module (USART_IF_nnn) OR'ed together.

◆ USART_IntDisable()

void USART_IntDisable ( USART_TypeDef * usart,
uint32_t flags
)
inline

Disable one or more USART interrupts.

Parameters
[in] usart Pointer to USART/UART peripheral register block.
[in] flags USART/UART interrupt source(s) to disable. Use one or more valid interrupt flags for the USART module (USART_IF_nnn) OR'ed together.

◆ USART_IntEnable()

void USART_IntEnable ( USART_TypeDef * usart,
uint32_t flags
)
inline

Enable one or more USART interrupts.

Note
Depending on the use, a pending interrupt may already be set prior to enabling the interrupt. To ignore a pending interrupt, consider using USART_IntClear() prior to enabling the interrupt.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
[in] flags USART/UART interrupt source(s) to enable. Use one or more valid interrupt flags for the USART module (USART_IF_nnn) OR'ed together.

◆ USART_IntGet()

uint32_t USART_IntGet ( USART_TypeDef * usart )
inline

Get pending USART interrupt flags.

Note
The event bits are not cleared by the use of this function.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
USART/UART interrupt source(s) pending. Returns one or more valid interrupt flags for the USART module (USART_IF_nnn) OR'ed together.

◆ USART_IntGetEnabled()

uint32_t USART_IntGetEnabled ( USART_TypeDef * usart )
inline

Get enabled and pending USART interrupt flags.

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

Parameters
[in] usart Pointer to USART/UART peripheral register block.
Note
Interrupt flags are not cleared by the use of this function.
Returns
Pending and enabled USART interrupt sources. The return value is the bitwise AND combination of
  • the OR combination of enabled interrupt sources in USARTx_IEN_nnn register (USARTx_IEN_nnn) and
  • the OR combination of valid interrupt flags of the USART module (USARTx_IF_nnn).

◆ USART_IntSet()

void USART_IntSet ( USART_TypeDef * usart,
uint32_t flags
)
inline

Set one or more pending USART interrupts from SW.

Parameters
[in] usart Pointer to USART/UART peripheral register block.
[in] flags USART/UART interrupt source(s) to set to pending. Use one or more valid interrupt flags for the USART module (USART_IF_nnn) OR'ed together.

◆ USART_StatusGet()

uint32_t USART_StatusGet ( USART_TypeDef * usart )
inline

Get USART STATUS register.

Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
STATUS register value.

◆ USART_Reset()

void USART_Reset ( USART_TypeDef * usart )

Reset USART/UART to the same state that it was in after a hardware reset.

Parameters
[in] usart A pointer to USART/UART peripheral register block.

◆ USART_Rx()

uint8_t USART_Rx ( USART_TypeDef * usart )

Receive one 4-8 bit frame, (or part of 10-16 bit frame).

This function is normally used to receive one frame when operating with frame length 4-8 bits. See USART_RxExt() for reception of 9 bit frames.

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

Note
This function will stall if the buffer is empty until data is received. Alternatively, the user can explicitly check whether data is available. If data is available, call USART_RxDataGet() to read the RXDATA register directly.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDouble()

uint16_t USART_RxDouble ( USART_TypeDef * usart )

Receive two 4-8 bit frames or one 10-16 bit frame.

This function is normally used to receive one frame when operating with frame length 10-16 bits. See USART_RxDoubleExt() for reception of two 9 bit frames.

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

Note
This function will stall if the buffer is empty until data is received. Alternatively, the user can explicitly check whether data is available. If data is available, call USART_RxDoubleGet() to read the RXDOUBLE register directly.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDoubleExt()

uint32_t USART_RxDoubleExt ( USART_TypeDef * usart )

Receive two 4-9 bit frames, or one 10-16 bit frame with extended information.

This function is normally used to receive one frame when operating with frame length 10-16 bits and additional RX status information is required.

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

Note
This function will stall if buffer is empty until data is received. Alternatively, the user can explicitly check whether data is available. If data is available, call USART_RxDoubleXGet() to read the RXDOUBLEX register directly.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxExt()

uint16_t USART_RxExt ( USART_TypeDef * usart )

Receive one 4-9 bit frame (or part of 10-16 bit frame) with extended information.

This function is normally used to receive one frame when operating with frame length 4-9 bits and additional RX status information is required.

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

Note
This function will stall if the buffer is empty until data is received. Alternatively, the user can explicitly check whether data is available. If data is available, call USART_RxDataXGet() to read the RXDATAX register directly.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDataGet()

uint8_t USART_RxDataGet ( USART_TypeDef * usart )
inline

Receive one 4-8 bit frame, (or part of 10-16 bit frame).

This function is used to quickly receive one 4-8 bits frame by reading the RXDATA register directly, without checking the STATUS register for the RXDATAV flag. This can be useful from the RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read the received data. Please refer to USART_RxDataXGet() for reception of 9 bit frames.

Note
Since this function does not check whether 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 USART_Rx() is normally a better choice if the validity of the RXDATA register is not certain.
Notice that possible parity/stop bits in asynchronous mode are not considered part of specified frame bit length.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDoubleGet()

uint16_t USART_RxDoubleGet ( USART_TypeDef * usart )
inline

Receive two 4-8 bit frames, or one 10-16 bit frame.

This function is used to quickly receive one 10-16 bits frame or two 4-8 bit frames by reading the RXDOUBLE register directly, without checking the STATUS register for the RXDATAV flag. This can be useful from the RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read the received data. This function is normally used to receive one frame when operating with frame length 10-16 bits. Please refer to USART_RxDoubleXGet() for reception of two 9 bit frames.

Note
Since this function does not check whether the RXDOUBLE 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 USART_RxDouble() is normally a better choice if the validity of the RXDOUBLE register is not certain.
Notice that possible parity/stop bits in asynchronous mode are not considered part of specified frame bit length.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDoubleXGet()

uint32_t USART_RxDoubleXGet ( USART_TypeDef * usart )
inline

Receive two 4-9 bit frames, or one 10-16 bit frame with extended information.

This function is used to quickly receive one 10-16 bits frame or two 4-9 bit frames by reading the RXDOUBLEX register directly, without checking the STATUS register for the RXDATAV flag. This can be useful from the RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read the received data.

Note
Since this function does not check whether the RXDOUBLEX 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 USART_RxDoubleExt() is normally a better choice if the validity of the RXDOUBLEX register is not certain.
Notice that possible parity/stop bits in asynchronous mode are not considered part of specified frame bit length.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
Data received.

◆ USART_RxDataXGet()

uint16_t USART_RxDataXGet ( USART_TypeDef * usart )
inline

Receive one 4-9 bit frame, (or part of 10-16 bit frame) with extended information.

This function is used to quickly receive one 4-9 bit frame, (or part of 10-16 bit frame) with extended information by reading the RXDATAX register directly, without checking the STATUS register for the RXDATAV flag. This can be useful from the RXDATAV interrupt handler, i.e., waiting is superfluous, in order to quickly read the received data.

Note
Since this function does not check whether 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 USART_RxExt() is normally a better choice if the validity of the RXDATAX register is not certain.
Notice that possible parity/stop bits in asynchronous mode are not considered part of specified frame bit length.
Parameters
[in] usart Pointer to USART/UART peripheral register block.
Returns
Data received.

◆ USART_SpiTransfer()

uint8_t USART_SpiTransfer ( USART_TypeDef * usart,
uint8_t data
)

Perform one 8 bit frame SPI transfer.

Note
This function will stall if the transmit buffer is full. When a transmit buffer becomes available, data is written and the function will wait until data is fully transmitted. The SPI return value is then read out and returned.
Parameters
[in] usart A pointer to the USART peripheral register block.
[in] data Data to transmit.
Returns
Data received.

◆ USART_Tx()

void USART_Tx ( USART_TypeDef * usart,
uint8_t data
)

Transmit one 4-9 bit frame.

Depending on the frame length configuration, 4-8 (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 CTRL register, BIT8DV field. See USART_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 part of a specified frame bit length.

Note
This function will stall if the buffer is full until the buffer becomes available.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] data Data to transmit. See details above for more information.

◆ USART_TxDouble()

void USART_TxDouble ( USART_TypeDef * usart,
uint16_t data
)

Transmit two 4-9 bit frames or one 10-16 bit frame.

Depending on the frame length configuration, 4-8 (least significant) bits from each byte in data are transmitted. If frame length is 9, 8 bits are transmitted from each byte in data adding one bit as specified by the CTRL register, BIT8DV field, to each byte. See USART_TxDoubleExt() for transmitting two 9 bit frames with full control of all 9 bits.

If the frame length is 10-16, 10-16 (least significant) bits from data are transmitted.

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

Note
This function will stall if the buffer is full until the buffer becomes available.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] data Data to transmit, the least significant byte holds the frame transmitted first. See details above for more info.

◆ USART_TxDoubleExt()

void USART_TxDoubleExt ( USART_TypeDef * usart,
uint32_t data
)

Transmit two 4-9 bit frames or one 10-16 bit frame with extended control.

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

Note
This function will stall if the buffer is full until the buffer becomes available.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] data Data to transmit with extended control. Contains two 16 bit words concatenated. Least significant word holds the frame transmitted first. If the frame length is 4-9, two frames with 4-9 least significant bits from each 16 bit word are transmitted.
If the frame length is 10-16 bits, 8 data bits are taken from the least significant 16 bit word and the remaining bits from the other 16 bit word.
Additional control bits are available as documented in the reference manual (set to 0 if not used). For 10-16 bit frame length, these control bits are taken from the most significant 16 bit word.

◆ USART_TxExt()

void USART_TxExt ( USART_TypeDef * usart,
uint16_t data
)

Transmit one 4-9 bit frame with extended control.

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

Note
This function will stall if the buffer is full until the buffer becomes available.
Parameters
[in] usart A pointer to the USART/UART peripheral register block.
[in] data Data to transmit with extended control. Least significant bit contains frame bits. Additional control bits are available as documented in the reference manual (set to 0 if not used).

Macro Definition Documentation

◆ USART_INITASYNC_DEFAULT

#define USART_INITASYNC_DEFAULT
Value:
{ \
usartEnable, /* Enable RX/TX when initialization is complete. */ \
0, /* Use current configured reference clock for configuring baud rate. */ \
115200, /* 115200 bits/s. */ \
usartOVS16, /* 16x oversampling. */ \
usartDatabits8, /* 8 data bits. */ \
usartNoParity, /* No parity. */ \
usartStopbits1, /* 1 stop bit. */ \
false, /* Do not disable majority vote. */ \
false, /* Not USART PRS input mode. */ \
0, /* PRS channel 0. */ \
false, /* Auto CS functionality enable/disable switch */ \
0, /* Auto CS Hold cycles */ \
0, /* Auto CS Setup cycles */ \
usartHwFlowControlNone /* No HW flow control */ \
}

Default configuration for USART asynchronous initialization structure.

◆ USART_INITPRSTRIGGER_DEFAULT

#define USART_INITPRSTRIGGER_DEFAULT
Value:
{ \
false, /* Do not enable autoTX triggering. */ \
false, /* Do not enable receive triggering. */ \
false, /* Do not enable transmit triggering. */ \
0 /* Set default channel to zero. */ \
}

Default configuration for USART PRS triggering structure.

◆ USART_INITSYNC_DEFAULT

#define USART_INITSYNC_DEFAULT
Value:
{ \
usartEnable, /* Enable RX/TX when initialization is complete. */ \
0, /* Use current configured reference clock for configuring baud rate. */ \
1000000, /* 1 Mbits/s. */ \
usartDatabits8, /* 8 databits. */ \
true, /* Master mode. */ \
false, /* Send least significant bit first. */ \
usartClockMode0, /* Clock idle low, sample on rising edge. */ \
false, /* Not USART PRS input mode. */ \
0, /* PRS channel 0. */ \
false, /* No AUTOTX mode. */ \
false, /* No AUTOCS mode. */ \
0, /* Auto CS Hold cycles. */ \
0 /* Auto CS Setup cycles. */ \
}

Default configuration for USART sync initialization structure.

◆ USART_INITIRDA_DEFAULT

#define USART_INITIRDA_DEFAULT
Value:
{ \
{ \
usartEnable, /* Enable RX/TX when initialization is complete. */ \
0, /* Use current configured reference clock for configuring baud rate. */ \
115200, /* 115200 bits/s. */ \
usartOVS16, /* 16x oversampling. */ \
usartDatabits8, /* 8 data bits. */ \
usartEvenParity, /* Even parity. */ \
usartStopbits1, /* 1 stop bit. */ \
false, /* Do not disable majority vote. */ \
false, /* Not USART PRS input mode. */ \
0, /* PRS channel 0. */ \
false, /* Auto CS functionality enable/disable switch */ \
0, /* Auto CS Hold cycles */ \
0, /* Auto CS Setup cycles */ \
usartHwFlowControlNone /* No HW flow control */ \
}, \
false, /* Rx invert disabled. */ \
false, /* Filtering disabled. */ \
usartIrDAPwTHREE, /* Pulse width is set to ONE. */ \
false, /* Routing to PRS is disabled. */ \
0 /* PRS channel 0. */ \
}

Default configuration for IrDA mode initialization structure.

◆ USART_INITI2S_DEFAULT

#define USART_INITI2S_DEFAULT
Value:
{ \
{ \
usartEnableTx, /* Enable TX when init completed. */ \
0, /* Use current configured reference clock for configuring baudrate. */ \
1000000, /* Baudrate 1M bits/s. */ \
usartDatabits16, /* 16 databits. */ \
true, /* Operate as I2S master. */ \
true, /* Most significant bit first. */ \
usartClockMode0, /* Clock idle low, sample on rising edge. */ \
false, /* Don't enable USARTRx via PRS. */ \
usartPrsRxCh0, /* PRS channel selection (dummy). */ \
false, /* Disable AUTOTX mode. */ \
false, /* No AUTOCS mode */ \
0, /* Auto CS Hold cycles */ \
0 /* Auto CS Setup cycles */ \
}, \
usartI2sFormatW16D16, /* 16-bit word, 16-bit data */ \
true, /* Delay on I2S data. */ \
false, /* No DMA split. */ \
usartI2sJustifyLeft, /* Data is left-justified within the frame */ \
false /* Stereo mode. */ \
}

Default configuration for I2S mode initialization structure.

Typedef Documentation

◆ USART_PRS_Channel_t

typedef uint8_t USART_PRS_Channel_t

PRS Channel type.

Enumeration Type Documentation

◆ USART_Databits_TypeDef

enum USART_Databits_TypeDef

Databit selection.

Enumerator
usartDatabits4

4 data bits (not available for UART).

usartDatabits5

5 data bits (not available for UART).

usartDatabits6

6 data bits (not available for UART).

usartDatabits7

7 data bits (not available for UART).

usartDatabits8

8 data bits.

usartDatabits9

9 data bits.

usartDatabits10

10 data bits (not available for UART).

usartDatabits11

11 data bits (not available for UART).

usartDatabits12

12 data bits (not available for UART).

usartDatabits13

13 data bits (not available for UART).

usartDatabits14

14 data bits (not available for UART).

usartDatabits15

15 data bits (not available for UART).

usartDatabits16

16 data bits (not available for UART).

◆ USART_Enable_TypeDef

enum USART_Enable_TypeDef

Enable selection.

Enumerator
usartDisable

Disable both receiver and transmitter.

usartEnableRx

Enable receiver only, transmitter disabled.

usartEnableTx

Enable transmitter only, receiver disabled.

usartEnable

Enable both receiver and transmitter.

◆ USART_OVS_TypeDef

enum USART_OVS_TypeDef

Oversampling selection, used for asynchronous operation.

Enumerator
usartOVS16

16x oversampling (normal).

usartOVS8

8x oversampling.

usartOVS6

6x oversampling.

usartOVS4

4x oversampling.

◆ USART_Parity_TypeDef

enum USART_Parity_TypeDef

Parity selection, mainly used for asynchronous operation.

Enumerator
usartNoParity

No parity.

usartEvenParity

Even parity.

usartOddParity

Odd parity.

◆ USART_Stopbits_TypeDef

enum USART_Stopbits_TypeDef

Stop bits selection, used for asynchronous operation.

Enumerator
usartStopbits0p5

0.5 stop bits.

usartStopbits1

1 stop bits.

usartStopbits1p5

1.5 stop bits.

usartStopbits2

2 stop bits.

◆ USART_HwFlowControl_TypeDef

enum USART_HwFlowControl_TypeDef

Hardware Flow Control Selection.

◆ USART_ClockMode_TypeDef

enum USART_ClockMode_TypeDef

Clock polarity/phase mode.

Enumerator
usartClockMode0

Clock idle low, sample on rising edge.

usartClockMode1

Clock idle low, sample on falling edge.

usartClockMode2

Clock idle high, sample on falling edge.

usartClockMode3

Clock idle high, sample on rising edge.

◆ USART_IrDAPw_Typedef

enum USART_IrDAPw_Typedef

Pulse width selection for IrDA mode.

Enumerator
usartIrDAPwONE

IrDA pulse width is 1/16 for OVS=0 and 1/8 for OVS=1.

usartIrDAPwTWO

IrDA pulse width is 2/16 for OVS=0 and 2/8 for OVS=1.

usartIrDAPwTHREE

IrDA pulse width is 3/16 for OVS=0 and 3/8 for OVS=1.

usartIrDAPwFOUR

IrDA pulse width is 4/16 for OVS=0 and 4/8 for OVS=1.

◆ USART_I2sFormat_TypeDef

enum USART_I2sFormat_TypeDef

I2S format selection.

Enumerator
usartI2sFormatW32D32

32-bit word, 32-bit data.

usartI2sFormatW32D24M

32-bit word, 32-bit data with 8 lsb masked.

usartI2sFormatW32D24

32-bit word, 24-bit data.

usartI2sFormatW32D16

32-bit word, 16-bit data.

usartI2sFormatW32D8

32-bit word, 8-bit data.


usartI2sFormatW16D16

16-bit word, 16-bit data.

usartI2sFormatW16D8

16-bit word, 8-bit data.


usartI2sFormatW8D8

8-bit word, 8-bit data.


◆ USART_I2sJustify_TypeDef

enum USART_I2sJustify_TypeDef

I2S frame data justify.

Enumerator
usartI2sJustifyLeft

Data is left-justified within the frame.


usartI2sJustifyRight

Data is right-justified within the frame.