Posted on June 27, 2016 at 21:31Hi, I am new at programming ARM microcontrollers and I use stm32f4 discovery board. I have tried to program blinking of the 4 user LEDs on the board so that it should change its state every 10 seconds assuming 16MHz internal oscilator. I have set prescaller to 16000, thus I have got 1000Hz and autoreload register to 10000, but when I run the program, the LEDs change their state every approximately 6 seconds. It behaves like the oscilator is approximately 26.6MHz, but it is impossible. Has anyone experience with similar problem? My code is here:
#include ''stm32f4xx.h''
#include ''stm32f4xx_conf.h''
#include ''misc.h''
#include ''core_cmInstr.h''
char state = 0;
void TIM7_IRQHandler(void)
{
if (state == 0)
{
GPIO_SetBits(GPIOD, GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15); //LEDs on
state = 1;
}
else
{
GPIO_ResetBits(GPIOD, GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15); //LEDs off
state = 0;
}
TIM_ClearITPendingBit(TIM7, TIM_IT_Update);
return;
}
int main(void)
{
//timer7 interrupt settings
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel = TIM7_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = (uint8_t)1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority =(uint8_t)1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
//timer7 settings
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM7, ENABLE);
TIM_PrescalerConfig(TIM7, (uint16_t)16000, TIM_PSCReloadMode_Immediate);
TIM_SelectOnePulseMode(TIM7, TIM_OPMode_Repetitive);
TIM_SetAutoreload(TIM7, (uint32_t)10000);
TIM_UpdateRequestConfig(TIM7, TIM_UpdateSource_Global);
TIM_UpdateDisableConfig(TIM7, DISABLE);
TIM_ITConfig(TIM7, TIM_IT_Update, ENABLE);
TIM_Cmd(TIM7, ENABLE);
//GPIO settings
GPIO_InitTypeDef GPIO_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOD, &GPIO_InitStructure);
GPIO_SetBits(GPIOD, GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15); //LEDs on
while(1)
{
__NOP();
}
}
