Posted on August 11, 2013 at 10:47 From the original project i worked on, i used the USART1 when i found the problem. the thing is that USART1 only has a small shift in timing, not as large as the USART3. So my project has worked 10% of the time, and it took some time before a found the problem. So a changed my 
I added a timing reference picture for 9600 Baud, and here we can see that i hole frame should be 1024uS 
Next Step I know that it has to do with the clock settings, so i put together a example with Timer3(APB1) and Timer10(APB2). I made it so both should output PWM on one pin each so i could check so both APB1 and APB2 is running as thy should. because USART1 is on the APB2 bus and USART3 is on APB1. 
Both Tim3 and Tim10 is set to 530 KHz I initialize the SystemInit(); at startup. 
here we can see that TIM3 CH1 is the selected one, and the Frequency show 5375KHz. And TIM10 CH1 is a bit of in phase, but we can see it has the same timing and frequency as TIM3 . So the APB1 and APB2 seams to be running at the right frequency. but i still get 1124uS frame timing for USART1 and 3255uSframe timing on USART3 when thy are set to 9600baud my settings from the clock configuration that i am using 
the Timer3 and 10 code
previously
example to switch to USART1 again, so i can show the problem. I initialize the SystemInit(); at startup. And the picture shows the USART1 TX output at 9600 baud setting in STM32 I added a timing reference picture for 9600 Baud, and here we can see that i hole frame should be 1024uS Next Step I know that it has to do with the clock settings, so i put together a example with Timer3(APB1) and Timer10(APB2). I made it so both should output PWM on one pin each so i could check so both APB1 and APB2 is running as thy should. because USART1 is on the APB2 bus and USART3 is on APB1. Both Tim3 and Tim10 is set to 530 KHz I initialize the SystemInit(); at startup. here we can see that TIM3 CH1 is the selected one, and the Frequency show 5375KHz. And TIM10 CH1 is a bit of in phase, but we can see it has the same timing and frequency as TIM3 . So the APB1 and APB2 seams to be running at the right frequency. but i still get 1124uS frame timing for USART1 and 3255uSframe timing on USART3 when thy are set to 9600baud my settings from the clock configuration that i am using the Timer3 and 10 code /**
* @brief Configure the TIM10 Ouput Channels.
* @param None
* @retval None
*/
void TIM_Config_TIM10(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
uint16_t CCR1_Val = 333;
uint16_t PrescalerValue = 0;
/* TIM10 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM10, ENABLE);
/* GPIOF clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
/* GPIOF Configuration: TIM10 CH1 (PB8) */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 ;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/* Connect TIM pins to AF3 */
GPIO_PinAFConfig(GPIOB, GPIO_PinSource8, GPIO_AF_TIM10);
/* ---------------------------------------------------------------------------
TIM10 Configuration: generate 1 PWM signal:
In this example TIM10 input clock (TIM10CLK) is set to 2 * APB2 clock (PCLK2),
since APB2 prescaler is different from 1.
TIM10CLK = 2 * PCLK2
PCLK2 = HCLK / 2
=> TIM10CLK = HCLK = SystemCoreClock
To get TIM10 counter clock at 21 MHz, the prescaler is computed as follows:
Prescaler = (TIM10CLK / TIM10 counter clock) - 1
Prescaler = (SystemCoreClock /21 MHz) - 1
To get TIM10 output clock at 530 KHz, the period (TIM10_ARR) is computed as follows:
ARR = (TIM10 counter clock / TIM10 output clock) - 1
= 665
TIM10 Channel1 duty cycle = (TIM10_CCR1/ TIM10_ARR)* 100 = 50%
Note:
SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.
Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
function to update SystemCoreClock variable value. Otherwise, any configuration
based on this variable will be incorrect.
--------------------------------------------------------------------------- */
CCR1_Val = 333;
/* Compute the prescaler value */
PrescalerValue = (uint16_t) (168000000 / 21000000) - 1;
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 665;
TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM10, &TIM_TimeBaseStructure);
/* PWM1 Mode configuration: Channel1 */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM10, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM10, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM10, ENABLE);
/* TIM10 enable counter */
TIM_Cmd(TIM10, ENABLE);
}
/**
* @brief Configure the TIM10 Ouput Channels.
* @param None
* @retval None
*/
void TIM_Config_TIM3(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
uint16_t CCR1_Val = 333;
uint16_t PrescalerValue = 0;
uint32_t TIM3CLK = 0;
/* TIM3 clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
/* GPIOC clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* GPIOF Configuration: TIM3 CH1 (PC6) */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 ;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
GPIO_Init(GPIOC, &GPIO_InitStructure);
/* Connect TIM pins to AF2 */
GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);
/* ---------------------------------------------------------------------------
TIM3 Configuration: generate 1 PWM signal:
In this example TIM3 input clock (TIM3CLK) is set to 2 * APB1 clock (PCLK1),
since APB1 prescaler is different from 1.
TIM3CLK = 2 * PCLK1
PCLK1 = HCLK / 4
=> TIM3CLK = HCLK/2 = SystemCoreClock/2
To get TIM3 counter clock at 21 MHz, the prescaler is computed as follows:
Prescaler = (TIM3CLK / TIM3 counter clock) - 1
Prescaler = (TIM3CLK /21 MHz) - 1
To get TIM3 output clock at 530 KHz, the period (TIM3_ARR) is computed as follows:
ARR = (TIM3 counter clock / TIM3 output clock) - 1
= 665
TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR)* 100 = 50%
Note:
SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.
Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
function to update SystemCoreClock variable value. Otherwise, any configuration
based on this variable will be incorrect.
--------------------------------------------------------------------------- */
CCR1_Val = 333;
TIM3CLK = 84000000;
/* Compute the prescaler value */
PrescalerValue = (uint16_t) (TIM3CLK / 21000000) - 1;
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 665;
TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
/* PWM1 Mode configuration: Channel1 */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM3, ENABLE);
/* TIM3 enable counter */
TIM_Cmd(TIM3, ENABLE);
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Posted on August 12, 2013 at 09:25 
At second breakpoint (all in decimal) 
Thats weird, you can se that HSI_VALUE (T1) = 8MHz but i don't think the clock is running at 525MHz :) i tested to change the HSI_VALUE to 1MHz result 
you can see that T1 = 1MHz, and the clockstatus has not changed at all so i debugged the function 
I debugged the code line by line and got (HSI_VALUE@8MHz) /* Get SYSCLK source -------------------------------------------------------*/ tmp = RCC->CFGR & RCC_CFGR_SWS; = 8 pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC) >> 22; =1 pllm = RCC->PLLCFGR & RCC_PLLCFGR_PLLM; =8 i change this part of the code (added a temp) so i could see the register data if (pllsource != 0) { /* HSE used as PLL clock source */ temp = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6); pllvco = (HSE_VALUE / pllm) * temp; } temp is set to 336 pllvco 1050000000 <- this is strange, becuse pllm = 8, temp=336 then if i calculate the HSE_VALUE from this a get 25MHz, hug ??? hmm oki I did not think this was possible, but while i debug check the HSE_VALUE in main.c and it says 8MHz and when it gos into the RCC_GetClocksFreq function in stm32f4xx_rcc.c i check the HSE_VALUE again, and now it says 25MHz the stm32f4xx.h is the only place a define the HSE_VALUE = 8MHz and i can not find any other defines in my code
Hi Clive.
Yes that was my first check. I added 2 lines in main.c so i could check the HSI_VALUE and added __NO_SYSTEM_INIT in preprocessor definition so i could check HSI_VALUE before theSystemInit();
The debugger says it is 8MHz, but it's strange because the UART timefram time do not change if a change the HSI_VALUE to something else, like 1MHzint main(void)
{ // Only used to check the osc reference values while debug so they are correct uint32_t T1 = HSE_VALUE; uint32_t T2 = HSI_VALUE; /* System Clocks Configuration **********************************************/ SystemInit(); I tested to fetch the clock data I debugged this codeint main(void)
{ // Only used to check the osc reference values while debug so they are correct uint32_t T1 = HSE_VALUE; uint32_t T2 = HSI_VALUE; uint8_t dummy = 0; RCC_ClocksTypeDef RCC_ClocksStatus; /* Configure the USART Baud Rate */ RCC_GetClocksFreq(&RCC_ClocksStatus); dummy = 1; <- I put the first breakpoint here /* System Clocks Configuration **********************************************/ SystemInit(); /* Configure the USART Baud Rate */ RCC_GetClocksFreq(&RCC_ClocksStatus); dummy = 2; <- I put the second breakpoint here and i got At first breakpoint (all in decimal) At second breakpoint (all in decimal) Thats weird, you can se that HSI_VALUE (T1) = 8MHz but i don't think the clock is running at 525MHz :) i tested to change the HSI_VALUE to 1MHz result you can see that T1 = 1MHz, and the clockstatus has not changed at all so i debugged the function RCC_GetClocksFreq(&RCC_ClocksStatus);
and got I debugged the code line by line and got (HSI_VALUE@8MHz) /* Get SYSCLK source -------------------------------------------------------*/ tmp = RCC->CFGR & RCC_CFGR_SWS; = 8 pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC) >> 22; =1 pllm = RCC->PLLCFGR & RCC_PLLCFGR_PLLM; =8 i change this part of the code (added a temp) so i could see the register data if (pllsource != 0) { /* HSE used as PLL clock source */ temp = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6); pllvco = (HSE_VALUE / pllm) * temp; } temp is set to 336 pllvco 1050000000 <- this is strange, becuse pllm = 8, temp=336 then if i calculate the HSE_VALUE from this a get 25MHz, hug ??? hmm oki I did not think this was possible, but while i debug check the HSE_VALUE in main.c and it says 8MHz and when it gos into the RCC_GetClocksFreq function in stm32f4xx_rcc.c i check the HSE_VALUE again, and now it says 25MHz the stm32f4xx.h is the only place a define the HSE_VALUE = 8MHz and i can not find any other defines in my code
