HI,
So I cannot seem to get the time base that I expect out of Timer 6. I have got timer working wiht the right freqnecy however I cannot seem to get timer 6 to work at the expected freqency. It seems to be running twice as fast to what I set it to.
I am running a 16 MHz internal, in the diagram attached you should find the rest of the RCC settings.
This is the code that goes with that diagram. I have checked it and it should all be good but maybe I missed something.
RCC->CR |= RCC_CR_HSEON; //HSE on
while((RCC->CR & RCC_CR_HSERDY) != RCC_CR_HSERDY); // Waiting for HSE to be ready
RCC->CR &= ~RCC_CR_PLLON; // Disable PLL
while((RCC->CR & RCC_CR_PLLRDY)== RCC_CR_PLLRDY); // Wait for pll to turn off
RCC->CFGR = RCC_CFGR_PLLSRC_HSE_PREDIV | RCC_CFGR_PLLMUL9 | RCC_CFGR_HPRE_DIV1 | RCC_CFGR_PPRE1_DIV2 | RCC_CFGR_PLLXTPRE_HSE_PREDIV_DIV2;//PLLSCR = HSE/2 , PLLMUL = x9 (72Mhz),AHB prescaler not devided, APB1 Clock /2 = 36MHz (Max=36MHz)
RCC->CR |= 0x01000000; // Turn on PLL on
while((RCC->CR & RCC_CR_PLLRDY) != RCC_CR_PLLRDY); // Waiting for PLL to be ready
FLASH->ACR |= FLASH_ACR_LATENCY_1; // Adjust flash speed for new frequency
RCC->CFGR |= RCC_CFGR_SW_PLL; // Set PLL as system clock
while((RCC->CFGR & RCC_CFGR_SWS_PLL) != RCC_CFGR_SWS_PLL); // Wait fpr pll to be used as system clock
RCC->CR &= ~RCC_CR_HSION; //Turning of HSI
while((RCC->CR & RCC_CR_HSIRDY) == RCC_CR_HSIRDY); // Wait for HSI to be off
This is the code for TIMER 6
RCC->APB1ENR |= RCC_APB1ENR_TIM6EN; // Enabling timer 6 clock, running at 72 MHz
TIM6->CR1 |= TIM_CR1_URS ; // Only Counter Overflow/Underflow generates an update interrupt or DMA reqwst
TIM6->PSC = 65535; // 72 MHz / 65535+1 = 1098.6 Hz = CK_CNT = Max output freuqnecy
TIM6->ARR = 101;
TIM6->DIER |= TIM_DIER_UIE; // TIM6 update interrupt enabled
NVIC_EnableIRQ(TIM6_DAC_IRQn); // enabling TIM6 global and DAC underrun error Interrupt
TIM6->CR1 |= TIM_CR1_CEN; // TIM6 Clock Enable
According to this, I should have a 72 MHz clock / 65536 = CK_CNT = 1098 Hz / 101 ticks =10.87 Hz
I then have an interrupt whihc goes through the values of a lookup table with 101 samples. Therefore = 10.87 Hz /101 = 0.1076 Hz =9.29 s. I however seem to be running twice as fast through this.
void TIM6_DAC_IRQHandler(void)
{
//Duty Cycles
TIM1->CCR1 = tableU[i];
TIM1->CCR2 = tableV[i];
TIM1->CCR3 = tableW[i];
i++;
//if we reached end of array
if (i == 101)
{
i = 0;
}
TIM6->SR = ~TIM_SR_UIF; // Clear interrupt
}
Can anyone spot any obvious errors?
Cheers
GG
