stm32f4 discovery timer 1 frequency issue

[d4ng3r09]

Posted on January 18, 2015 at 20:43

Hi,

I am using stm32f4 's timer 1 in pwm mode.I configured the board frequency using the excell clock configuration tool. I managed to provide TIM1 a clock source of 8 MHZ. Then i put 20 in timer 1 's prescaler and 8000 in the period so i can get 50 hz. .My problem is that the oscilloscope shows once the pwm configured a 100 hz signal. What am i doing wrong? Here is the summary of system_stm32f4xx.c and my timer configuration.

*=============================================================================
*=============================================================================
* Supported STM32F40xx/41xx/427x/437x devices
*-----------------------------------------------------------------------------
* System Clock source | HSI
*-----------------------------------------------------------------------------
* SYSCLK(Hz) | 16000000
*-----------------------------------------------------------------------------
* HCLK(Hz) | 8000000
*-----------------------------------------------------------------------------
* AHB Prescaler | 1
*-----------------------------------------------------------------------------
* APB1 Prescaler | 1
*-----------------------------------------------------------------------------
* APB2 Prescaler | 1
*-----------------------------------------------------------------------------
* HSE Frequency(Hz) | 25000000
*-----------------------------------------------------------------------------
* PLL_M | 25
*-----------------------------------------------------------------------------
* PLL_N | 192
*-----------------------------------------------------------------------------
* PLL_P | 6
*-----------------------------------------------------------------------------
* PLL_Q | 4
*-----------------------------------------------------------------------------
* PLLI2S_N | NA
*-----------------------------------------------------------------------------
* PLLI2S_R | NA
*-----------------------------------------------------------------------------
* I2S input clock | NA
*-----------------------------------------------------------------------------
* VDD(V) | 3.3
*-----------------------------------------------------------------------------
* Main regulator output voltage | Scale2 mode
*-----------------------------------------------------------------------------
* Flash Latency(WS) | 0
*-----------------------------------------------------------------------------
* Prefetch Buffer | OFF
*-----------------------------------------------------------------------------
* Instruction cache | ON
*-----------------------------------------------------------------------------
* Data cache | ON
*-----------------------------------------------------------------------------
* Require 48MHz for USB OTG FS, | Disabled
* SDIO and RNG clock |
*-----------------------------------------------------------------------------
*=============================================================================
Timer code:
uint16_t TimerPeriod = 0;
uint16_t Channel1Pulse=0 , Channel2Pulse=0 , Channel3Pulse=0 ,
Channel4Pulse=0 ;
void TIM_Config(void) {
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
/* GPIOA Configuration: Channel 1, 2, 3 and 4 as alternate function push-pull */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_11 | GPIO_Pin_13
| GPIO_Pin_14;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOE, &GPIO_InitStructure);
GPIO_Init(GPIOE, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource9, GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource11, GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource13, GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource14, GPIO_AF_TIM1);
TimerPeriod = 8000 - 1;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
TIM_TimeBaseStructure.TIM_Prescaler = 20 - 1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
/* Channel 1, 2,3 and 4 Configuration in PWM mode */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_Pulse = 0;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
//TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
TIM_OC2Init(TIM1, &TIM_OCInitStructure);
TIM_OC3Init(TIM1, &TIM_OCInitStructure);
TIM_OC4Init(TIM1, &TIM_OCInitStructure);
TIM1->CCR1 = Channel1Pulse;//PE9
TIM1->CCR2 = Channel2Pulse;//PE11
TIM1->CCR3 = Channel3Pulse;//PE13
TIM1->CCR4 = Channel4Pulse;//PE14
}

#pwm #stm32f4 #discovery #output

[Tesla DeLorean]

Posted on January 18, 2015 at 23:01

Your PLL settings are nonsensical, assuming you have a 25 MHz clock source, the system clock looks to be 32 MHz, however the STM32F4-DISCO has an 8 MHz clock source.

[d4ng3r09]

Posted on January 21, 2015 at 19:34

Sorry but i don t get it.As long as i get 8 MHZ at TIM 1 as shown in the clock configuration tool,how can the problem come from the PLL?

[Tesla DeLorean]

Posted on January 21, 2015 at 19:42

You've pasted a comment, I have no idea how your clocks are actually getting programmed, and where this 8 MHz is coming from. The comment is inconsistent with your description, I don't know how to proceed.

I'm apt to believe it's clocking at 16 MHz via the HSI. 16000000 / (20 * 8000) = 100 Hz

[d4ng3r09]

Posted on January 22, 2015 at 20:27Ok thank you anyway.