2016-06-27 12:31 PM
Hi, 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(); }}2016-06-27 04:53 PM
The clocks are usually configured in SystemInit() system_stm32f4xx.c, which is called prior to main() for most CMSIS implementations.
You should check the RCC registers, or do a GetClocks type call to pull data about what frequency the CPU and buses are clocking at.