clock.c

//
// COMP-GENG 421 - Tom Lupfer
//
// Clock module
//

#include "stm32l1xx_ll_bus.h"
#include "stm32l1xx_ll_rcc.h"
#include "stm32l1xx_ll_system.h"
#include "stm32l1xx_ll_utils.h"
#include "stm32l1xx_ll_pwr.h"

#include "main.h"
#include "clock.h"


// Configure the system clock
//
//  System Clock source	= PLL (HSI)
//  SYSCLK(Hz)			= 32000000
//  HCLK(Hz)			= 32000000
//  AHB Prescaler		= 1
//  APB1 Prescaler		= 1
//  APB2 Prescaler		= 1
//  HSI Frequency(Hz)	= 16000000
//  PLLMUL				= 6
//  PLLDIV				= 3
//  Flash Latency(WS)	= 1
//
void ClockInit(void)
{
	// Enable ACC64 access and set FLASH latency
	LL_FLASH_Enable64bitAccess();;
	LL_FLASH_SetLatency(LL_FLASH_LATENCY_1);

	// Set Voltage scale1 as MCU will run at 32MHz
	LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_PWR);
	LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);

	// Poll VOSF bit of in PWR_CSR. Wait until it is reset to 0
	while (LL_PWR_IsActiveFlag_VOSF() != 0)
		;

	// Enable HSI if not already activated
	if (LL_RCC_HSI_IsReady() == 0)
	{
		// HSI configuration and activation
		LL_RCC_HSI_Enable();
		while(LL_RCC_HSI_IsReady() != 1)
			;
	}

	// Main PLL configuration and activation
	LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSI, LL_RCC_PLL_MUL_6, LL_RCC_PLL_DIV_3);
	LL_RCC_PLL_Enable();
	while(LL_RCC_PLL_IsReady() != 1)
		;

	// Sysclk activation on the main PLL
	LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
	LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_PLL);
	while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_PLL)
		;

	// Set APB1 & APB2 prescaler
	LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_1);
	LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);

	// Set systick to 1ms in using frequency set to 32MHz
	// This frequency can be calculated through LL RCC macro
	// ex: __LL_RCC_CALC_PLLCLK_FREQ (HSI_VALUE, LL_RCC_PLL_MUL_6, LL_RCC_PLL_DIV_3);
	LL_Init1msTick(32000000);

	// Update CMSIS variable (which can be updated also through SystemCoreClockUpdate function)
	LL_SetSystemCoreClock(32000000);
}


void ClockWaitForTick(void)
{
	while (!(SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk))
		;

	SysTick->CTRL;	// clear COUNTFLAG
}