USART1 configuration (register)

schluchti · ‎2010-01-13

Posted on January 14, 2010 at 03:54

schluchti · ‎2011-05-17

Posted on May 17, 2011 at 13:37

Hi,

i want to write my own USART1 initialization. The sourcecode is attached below:

Code:

void usartSetup (void) {

GPIO_InitTypeDef GPIO_InitStructure;

RCC->APB2ENR |= RCC_APB2ENR_IOPAEN; // enable clock for GPIOA

GPIOA->CRH |= (0x0BUL << 4); // Tx (PA9) alt. out push-pull

GPIOA->CRH |= (0x04UL << 8); // Rx (PA10) in floating

RCC->APB2ENR |= RCC_APB2ENR_USART1EN; // enable clock for USART1

USART1->BRR = 8000000L/9600L; // set baudrate

USART1->CR1 |= (USART_CR1_RE | USART_CR1_TE); // RX, TX enable

USART1->CR1 |= USART_CR1_UE; // USART enable

/* GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure); */

}

The USART1 initialization only works, if I uncomment the code-block at the end of the subroutine. However, I want to get completely rid off the ST-Library... Does anyone know what I am missing?

Thanks,

Bernhard

chikos33 · ‎2011-05-17

Posted on May 17, 2011 at 13:37

Hi,

The main difference between your code and library code, is that they clear the configuration bits before doing the |= .

So try first to clear GPIOA->CRH register (or at least the PA9 & PA10 configuration bits):

GPIOA->CRH &= ~(0x00F0); /* Clear PA9 configuration bits */

GPIOA->CRH |= (0x00B0); /* Set AF Push Pull mode, 50 MHz for PA9 */

GPIOA->CRH &= ~(0x0F00); /* Clear PA10 configuration bits */

GPIOA->CRH |= (0x0400); /* Set Input floating mode for PA10 */

Good luck.

schluchti · ‎2011-05-17

Posted on May 17, 2011 at 13:37

Hi,

thanks a lot - it worked!

chikos33 · ‎2011-05-17

Posted on May 17, 2011 at 13:37

I'm glad for you 🙂