USART Public APIs

Functions
void	usart_init (USART_CFG_ts *usart_cfg)
	Initializes the USART peripheral with the given configuration.
void	usart_deinit (USART_REGDEF_ts const *instance)
	Deinitializes the USART peripheral, disables its NVIC interrupt, and disables its clock.
void	usart_send (USART_REGDEF_ts *instance, uint8_t *tx_buffer, uint32_t len)
	Blocking USART transmit.
void	usart_receive (USART_REGDEF_ts const *instance, uint8_t *rx_buffer, uint32_t len)
	Blocking USART receive.
void	usart_set_transmission (USART_REGDEF_ts *instance, EN_STATUS_te en_status)
	Enables or disables the USART transmitter.
void	usart_set_reception (USART_REGDEF_ts *instance, EN_STATUS_te en_status)
	Enables or disables the USART receiver.
void	usart_get_name (USART_REGDEF_ts const *instance, char *name)
	Returns the name string of a USART peripheral instance.

Detailed Description

Function Documentation

usart_init()

void usart_init

(

USART_CFG_ts *

usart_cfg

)

Initializes the USART peripheral with the given configuration.

See also

usart_init

Definition at line 28 of file stm32f401re_usart.c.

                                         {
    // Enable peripheral clock
    usart_set_pclk(usart_cfg->instance, ENABLE);
 
    // Configure data word length (8 or 9 bit)
    usart_cfg->instance->USART_CR1 &= ~(0x1 << USART_CR1_M);
    usart_cfg->instance->USART_CR1 |= (usart_cfg->frame_data_bits << USART_CR1_M);
 
    // Configure stop bit count
    usart_cfg->instance->USART_CR2 &= ~(0x3 << USART_CR2_STOP);
    usart_cfg->instance->USART_CR2 |= (usart_cfg->frame_stop_bits << USART_CR2_STOP);
 
    // Compute and write BRR from peripheral clock and baud rate
    usart_set_baud_rate(usart_cfg);
 
    // Configure oversampling ratio
    usart_cfg->instance->USART_CR1 &= ~(0x1 << USART_CR1_OVER8);
    usart_cfg->instance->USART_CR1 |= (usart_cfg->oversampling << USART_CR1_OVER8);
 
    // Configure parity
    if(usart_cfg->parity != USART_PARITY_DISABLED) {
        usart_cfg->instance->USART_CR1 |= (0x1 << USART_CR1_PCE);
 
        if(usart_cfg->parity == USART_PARITY_EVEN) {
            usart_cfg->instance->USART_CR1 &= ~(0x1 << USART_CR1_PS);
        }
        else if(usart_cfg->parity == USART_PARITY_ODD) {
            usart_cfg->instance->USART_CR1 |= (0x1 << USART_CR1_PS);
        }
    }
 
    // Configure hardware flow control (RTS + CTS)
    if(usart_cfg->hw_flow_control == USART_HW_FLOW_CONTROL_ENABLED) {
        usart_cfg->instance->USART_CR3 |= (0x1 << USART_CR3_CTSE);
        usart_cfg->instance->USART_CR3 |= (0x1 << USART_CR3_RTSE);
    }
 
    // Configure sample bit method
    usart_cfg->instance->USART_CR3 &= ~(0x1 << USART_CR3_ONEBIT);
    usart_cfg->instance->USART_CR3 |= (usart_cfg->sample_bit << USART_CR3_ONEBIT);
 
    if(usart_cfg->mode == USART_MODE_SYNC) {
        // LBCL, CPHA, CPOL, CLKEN — not yet implemented
    }
 
    // Enable RXNE interrupt and NVIC line if requested
    if(usart_cfg->interrupt_en == USART_INTERRUPT_EN_TRUE) {
        usart_cfg->instance->USART_CR1 |= (0x1 << USART_CR1_RXNEIE);
 
        if(usart_cfg->instance == USART1) {
            nvic_set_interrupt(USART1_IRQn, ENABLE);
        }
        else if(usart_cfg->instance == USART2) {
            nvic_set_interrupt(USART2_IRQn, ENABLE);
        }
        else if(usart_cfg->instance == USART6) {
            nvic_set_interrupt(USART6_IRQn, ENABLE);
        }
    }
 
    // Enable the USART peripheral
    usart_cfg->instance->USART_CR1 |= (0x1 << USART_CR1_UE);
}

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usart_deinit()

void usart_deinit

(

USART_REGDEF_ts const *

instance

)

Deinitializes the USART peripheral, disables its NVIC interrupt, and disables its clock.

See also

usart_deinit

Definition at line 93 of file stm32f401re_usart.c.

                                                   {
    if(instance == USART1) {
        rcc_reset_periph_apb2(RCC_APB2RSTR_USART1RST);
        nvic_set_interrupt(USART1_IRQn, DISABLE);
    }
    else if(instance == USART2) {
        rcc_reset_periph_apb1(RCC_APB1RSTR_USART2RST);
        nvic_set_interrupt(USART2_IRQn, DISABLE);
    }
    else if(instance == USART6) {
        rcc_reset_periph_apb2(RCC_APB2RSTR_USART6RST);
        nvic_set_interrupt(USART6_IRQn, DISABLE);
    }
 
    usart_set_pclk(instance, DISABLE);
}

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usart_send()

void usart_send	(	USART_REGDEF_ts *	instance,
		uint8_t *	tx_buffer,
		uint32_t	len )

Blocking USART transmit.

Blocking USART transmit. Sends len bytes from tx_buffer.

See also

usart_send

Definition at line 111 of file stm32f401re_usart.c.

                                                                             {
    while(len != 0) {
        while(!((instance->USART_SR >> USART_SR_TXE) & 0x1));
        instance->USART_DR = *tx_buffer;
        tx_buffer++;
        len--;
    }
    // Wait for TC to confirm the last byte has fully shifted out
    while(!((instance->USART_SR >> USART_SR_TC) & 0x1));
}

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usart_receive()

void usart_receive	(	USART_REGDEF_ts const *	instance,
		uint8_t *	rx_buffer,
		uint32_t	len )

Blocking USART receive.

Blocking USART receive. Reads len bytes into rx_buffer.

See also

usart_receive

Definition at line 123 of file stm32f401re_usart.c.

                                                                                      {
    while(len != 0) {
        while(!((instance->USART_SR >> USART_SR_RXNE) & 0x1));
        *rx_buffer = instance->USART_DR;
        rx_buffer++;
        len--;
    }
}

usart_set_transmission()

void usart_set_transmission	(	USART_REGDEF_ts *	instance,
		EN_STATUS_te	en_status )

Enables or disables the USART transmitter.

Enables or disables the USART transmitter (TE bit).

See also

usart_set_transmission

Definition at line 133 of file stm32f401re_usart.c.

                                                                               {
    instance->USART_CR1 &= ~(0x1 << USART_CR1_TE);
    instance->USART_CR1 |= (en_status << USART_CR1_TE);
}

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usart_set_reception()

void usart_set_reception	(	USART_REGDEF_ts *	instance,
		EN_STATUS_te	en_status )

Enables or disables the USART receiver.

Enables or disables the USART receiver (RE bit).

See also

usart_set_reception

Definition at line 139 of file stm32f401re_usart.c.

                                                                            {
    instance->USART_CR1 &= ~(0x1 << USART_CR1_RE);
    instance->USART_CR1 |= (en_status << USART_CR1_RE);
}

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usart_get_name()

void usart_get_name	(	USART_REGDEF_ts const *	instance,
		char *	name )

Returns the name string of a USART peripheral instance.

Returns the name string of a USART peripheral instance (e.g. "USART1").

See also

usart_get_name

Definition at line 145 of file stm32f401re_usart.c.

                                                                 {
    const char usart[] = "USART";
    uint8_t usart_len = get_str_len(usart);
    uint8_t pos_counter = 0;
 
    while(pos_counter != usart_len) {
        name[pos_counter] = usart[pos_counter];
        pos_counter++;
    }
 
    if(instance == USART1)      name[pos_counter] = '1';
    else if(instance == USART2) name[pos_counter] = '2';
    else if(instance == USART6) name[pos_counter] = '6';
    pos_counter++;
 
    name[pos_counter] = '\0';
}

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