USART on the STM32F051

carbolo · ‎2013-10-28

Posted on October 28, 2013 at 18:00

Hi Folks,

I am a little bit confused about the USART built in in the STM32F051. He is don`t talking to me although I am asking really polite.

This is my init-code:

RCC -> AHBENR |= (RCC_AHBENR_GPIOAEN);

//PA9

GPIOA->OSPEEDR |= (1UL<< 18); //MEDIUM SPEED

GPIOA->OTYPER &= ~(1UL<<9); //Push-pull

GPIOA->MODER |= (1UL<<19); //AF-Mode

GPIOA->AFR[1] |= (1UL << 4); //AF1 selected

//PA10

GPIOA->MODER |= (1UL<<21); // AF-Mode

GPIOA->AFR[1] |= (1UL<<8); // AF1 selected

RCC ->APB2ENR |= (1UL<<14);

USART1 -> CR1 = 0x0000000C; // enable TX and RX

USART1 -> CR2 = 0x00000000;

USART1 -> CR3 = 0x00000000;

USART1 -> BRR = 0x00000034;

USART1 -> CR1 |= (1UL << 0);

And this here is my TX-Routine:

void USART1_tx (char TX_char){

while (!(USART1 -> ISR & ( 1UL << 6))) { __NOP();}

USART1 -> TDR = TX_char;

}

Anyone an idea, where the problem is?

#usart #stm32f051

Tesla DeLorean · ‎2013-10-28

Posted on October 28, 2013 at 18:22

Anyone an idea, where the problem is?

I should care for register level code, but honestly I don't.

Do you see any data on the scope? Does the baud rate look right?

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carbolo · ‎2013-10-28

Posted on October 28, 2013 at 19:10

Do you see any data on the scope? Does the baud rate look right?

No, on the scope is nothing. It seems to be completely dead.

carbolo · ‎2013-10-28

Posted on October 28, 2013 at 19:51

Problem solved 🙂

add this line to the code and it works.

NVIC_EnableIRQ(USART1_IRQn);