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94 lines
2.5 KiB
94 lines
2.5 KiB
6 years ago
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/* LED blink project for the STM32L031 */
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#include "stm32l031xx.h"
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volatile unsigned long SysTickCount = 0;
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void __attribute__ ((interrupt, used)) SysTick_Handler(void)
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{
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SysTickCount++;
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if ( SysTickCount & 1 )
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GPIOA->BSRR = GPIO_BSRR_BS_13; /* atomic set PA13 */
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else
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GPIOA->BSRR = GPIO_BSRR_BR_13; /* atomic clr PA13 */
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}
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void setHSIClock()
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{
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/* test if the current clock source is something else than HSI */
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if ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_HSI)
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{
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/* enable HSI */
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RCC->CR |= RCC_CR_HSION;
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/* wait until HSI becomes ready */
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while ( (RCC->CR & RCC_CR_HSIRDY) == 0 )
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;
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/* enable the HSI "divide by 4" bit */
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RCC->CR |= (uint32_t)(RCC_CR_HSIDIVEN);
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/* wait until the "divide by 4" flag is enabled */
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while((RCC->CR & RCC_CR_HSIDIVF) == 0)
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;
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/* then use the HSI clock */
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RCC->CFGR = (RCC->CFGR & (uint32_t) (~RCC_CFGR_SW)) | RCC_CFGR_SW_HSI;
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/* wait until HSI clock is used */
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while ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_HSI)
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;
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}
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/* disable PLL */
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RCC->CR &= (uint32_t)(~RCC_CR_PLLON);
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/* wait until PLL is inactive */
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while((RCC->CR & RCC_CR_PLLRDY) != 0)
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;
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/* set latency to 1 wait state */
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FLASH->ACR |= FLASH_ACR_LATENCY;
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/* At this point the HSI runs with 4 MHz */
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/* Multiply by 16 device by 2 --> 32 MHz */
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RCC->CFGR = (RCC->CFGR & (~(RCC_CFGR_PLLMUL| RCC_CFGR_PLLDIV ))) | (RCC_CFGR_PLLMUL16 | RCC_CFGR_PLLDIV2);
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/* enable PLL */
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RCC->CR |= RCC_CR_PLLON;
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/* wait until the PLL is ready */
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while ((RCC->CR & RCC_CR_PLLRDY) == 0)
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;
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/* use the PLL has clock source */
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RCC->CFGR |= (uint32_t) (RCC_CFGR_SW_PLL);
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/* wait until the PLL source is active */
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while ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_PLL)
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;
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}
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int main()
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{
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setHSIClock();
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RCC->IOPENR |= RCC_IOPENR_IOPAEN; /* Enable clock for GPIO Port A */
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__NOP();
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__NOP();
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GPIOA->MODER &= ~GPIO_MODER_MODE13; /* clear mode for PA13 */
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GPIOA->MODER |= GPIO_MODER_MODE13_0; /* Output mode for PA13 */
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GPIOA->OTYPER &= ~GPIO_OTYPER_OT_13; /* no Push/Pull for PA13 */
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GPIOA->OSPEEDR &= ~GPIO_OSPEEDER_OSPEED13; /* low speed for PA13 */
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GPIOA->PUPDR &= ~GPIO_PUPDR_PUPD13; /* no pullup/pulldown for PA13 */
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GPIOA->BSRR = GPIO_BSRR_BR_13; /* atomic clr PA13 */
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SysTick->LOAD = 2000*500 - 1;
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SysTick->VAL = 0;
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SysTick->CTRL = 7; /* enable, generate interrupt (SysTick_Handler), do not divide by 2 */
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for(;;)
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;
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}
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