Posted on May 17, 2011 at 13:21Hello,
hopefully anyone can help me. I use the STM32F107VCT6 on the STM3210c-Eval board.
is it possible that the library function ''USART_Init'' works not correct?
I setup the USART 2 and use the lib-function and the Usart-init struct.
when I try to get the USART2 work with 9600 baud with the lib-function it doesn’t work.
But if I calculate the BRR Register values ''by hand'' it works fine!
I tried to get the system clocks with the lib-function ''RCC_GetClocksFreq'' but this function gives strange frequencies!
so maybe this function works not correct?
here the usart configuration:
-----------------------------
void SetUSART(){
/* The following example illustrates how to configure the USART1 */
/* Resets the USART1 registers to their default reset value */
RCC_ClocksTypeDef RCC_ClocksStatus; // for test
USART_DeInit(USART2);
USART_Cmd(USART2, ENABLE); // Enable USART 2
USART_InitStructure.USART_BaudRate = 9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
RCC_GetClocksFreq(&RCC_ClocksStatus); //for test
USART_Init(USART2, &USART_InitStructure); // init USART 2 with init structure
USART_ITConfig(USART2, USART_IT_RXNE , ENABLE); // Enables the USART2 Receive interrupt
USART_ITConfig(USART2, USART_IT_TXE, ENABLE); // Enables the USART2 Transmission Complete interrupt
/* Write to USART BRR */
USART2->BRR = 0x146; //20,36d
}
here the clock configuration:
-----------------------------
void SetCLK(){
ErrorStatus HSEStartUpStatus;
// RCC = Reset Clock Control
/* RCC system reset(for debug purpose) */
RCC_DeInit();
/* Enable HSE (>High speed external clock here: 25Mhz)*/
RCC_HSEConfig(RCC_HSE_ON); // switch to external oscillator
/* Disable Internal High Speed oscillator */
RCC_HSICmd(DISABLE);
/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp(); // check stable clock source
if(HSEStartUpStatus == SUCCESS){
/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_Div1); // System Clock
/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1); // peripheral clock 2
/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2); // peripheral clock 1
/* Flash 2 wait state */
FLASH_SetLatency(FLASH_Latency_2);
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
/* PLLCLK = 25MHz * 2 = 50 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_2); // PLL clock
/* Enable PLL */
RCC_PLLCmd(ENABLE); // enable the pll clock
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){} // wait until PLL is ready
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);// system clock = PLLCLOCK
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08){} // wait for ready clock
/* Configure HCLK such as HCLK = SYSCLK (AHB prescaler)*/
RCC_HCLKConfig(RCC_SYSCLK_Div1);
/* Configure PCLK1 such as PCLK1 = HCLK/16 (APB1 Prescaler)*/
// PCLK1 for: TIM2 and USART2
RCC_PCLK1Config(RCC_HCLK_Div16);
}
/* Enable GPIO and USART1 clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ALL, ENABLE);
/* Enable Timer2..7 clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_ALL, ENABLE);
}
thanks for any help
nullhere the clock configuration:
