STM32F3 Comp not writing to registers

[glenn0010]

Hi All,

So I've beern trying to write to the registers of the comparator 2 but when I debug , the values of the registers don't change. This leads me to believe that I have an issue getting the clock to the peripheral.

I have a 16 MHz external XTAL which according to the RCC config below (unless I made a mistake) should give me 32 MHz at the APB2 bus which is used fro COMP 2

XTAL (16 MHz) /2 = 8 Mhz -> PLL -> PLLMMUL = 8 MHz * 9 = 72 MHz -> HCLK = 72 MHz / 2 = 36 MHz -> PCLK2 (APB2) / 1 = 36 MHz

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

So assuming all the above is correct (Have DAC, ADC, UART, DMA phers working)

I must be missing something in the Comparator code below

// Setting the SYSCFG to enable a clock source for the comparator
	RCC->APB2RSTR |= RCC_APB2RSTR_SYSCFGRST;
	RCC->AHBENR |= RCC_AHBENR_GPIOAEN; // Enabling Port A clock
	GPIOA->MODER |= (1<<14) | (1<<15); // Configure PA7 as analog mode
	
 
	COMP2->CSR |= COMP2_CSR_COMP2INSEL_2; //Selecting inverting input as DAC1_CH1
	COMP2->CSR |= (1<<9); //Closing the switcch to connect PA7 to comparator non invering input (window mode)
	COMP2->CSR |= (1<<10); //Selecting Timer 1 break input as the output of the comparator (NEED TO VERIFY THIS)
	COMP2->CSR |= COMP2_CSR_COMP2BLANKING_0; //Selecting timer 1 OC5 as blanking source (NEED TO VERIFY THIS)
	COMP2->CSR |= (1<<30); //Selcting output as high

I am using the STM32F302R8 so looking at the manual, it only has comp 2 available!

If anyone could shed any light on it, I'd appricieate it !

Cheers

[Tesla DeLorean · Accepted solution]

APB2RSTR is the reset register, not the enable one.

[glenn0010]

Thanks Clive! That's when the autofill get's you. Such a silly mistake! Thanks

[turboscrew]

You seem to be resetting the SYSCFG-block instead of enabling it.

RCC->APB2RSTR |= RCC_APB2RSTR_SYSCFGRST;