This document discusses the operation of universal asynchronous receiver-transmitters (UARTs) on STM32F401 microprocessors. It describes UART character transmission and reception, fractional baud rate generation, and enabling interrupts using the nested vector interrupt controller. Examples are provided for configuring the baud rate and enabling interrupts on the STM32F401 UART.

1. Microprocessors systems
Vlasov Sergey
smvlasov@itmo.ru
Kirsanova Aleksandra

2. Universal asynchronous receiver-transmitter

3. Protocol

4. Operation

5. STM32F401 UART

6. STM32F401 UART

7. USART character description

8. Transmitter

9. Receiver

10. Fractional baud rate generation
Example:
• BAUDRATE = 19200
• APBx_FREQ = 42000000
//define APBx frequency
#define APBx_FREQ 42000000
//define UART Baudrate
#define BAUDRATE 19200
//In main function set UART baudrate
USARTx->BRR = APBx_FREQ/BAUDRATE

11. Interrupt

12. Nested Vector Interrupt Controller

13. Nested Vector Interrupt Controller

14. Nested Vector Interrupt Controller

15. Nested Vector Interrupt Controller

16. Nested Vector Interrupt Controller

17. Nested Vector Interrupt Controller

18. Enabling Interrupt
//Create USART2 Interrupt Handler
void USART2_IRQHandler(void)
{
//Some actions
}
int main()
{ RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
USART2->BRR = APB1/USART_BAUDRATE;
USART2->CR1 = USART_CR1_UE | //Enable UART
USART_CR1_TE | //Enable Transmitter
USART_CR1_RE | //Enable Receiver
USART_CR1_RXNEIE; //Enable interrupt in peripheral
NVIC_EnableIRQ(USART2_IRQn); //Enable Global interrupt
}

19. Thank you for attention
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