62 lines
1.8 KiB
C
62 lines
1.8 KiB
C
/* ledtick.c -- System Tick driven user LED blink
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** Copyright (c) 2020-2021 Renaud Fivet
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*/
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/* Memory locations defined by linker script */
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void __StackTop( void) ; /* __StackTop points after end of stack */
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void Reset_Handler( void) ; /* Entry point for execution */
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void SysTick_Handler( void) ;
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/* Interrupt vector table:
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* 1 Stack Pointer reset value
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* 15 System Exceptions
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* NN Device specific Interrupts
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*/
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typedef void (*isr_p)( void) ;
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isr_p const isr_vector[ 16] __attribute__((section(".isr_vector"))) = {
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__StackTop,
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/* System Exceptions */
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Reset_Handler,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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SysTick_Handler
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} ;
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#define SYSTICK ((volatile long *) 0xE000E010)
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#define SYSTICK_CSR SYSTICK[ 0]
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#define SYSTICK_RVR SYSTICK[ 1]
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#define SYSTICK_CVR SYSTICK[ 2]
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#define RCC ((volatile long *) 0x40021000)
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#define RCC_AHBENR RCC[ 5]
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#define RCC_AHBENR_IOPBEN 0x00040000 /* 18: I/O port B clock enable */
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#define GPIOB ((volatile long *) 0x48000400)
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#define GPIOB_MODER GPIOB[ 0]
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#define GPIOB_ODR GPIOB[ 5]
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void Reset_Handler( void) {
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/* By default SYSCLK == HSI [8MHZ] */
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/* SYSTICK */
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SYSTICK_RVR = 1000000 - 1 ; /* HBA / 8 */
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SYSTICK_CVR = 0 ;
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SYSTICK_CSR = 3 ; /* HBA / 8, Interrupt ON, Enable */
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/* SysTick_Handler will execute every 1s from now on */
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/* User LED ON */
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RCC_AHBENR |= RCC_AHBENR_IOPBEN ; /* Enable IOPB periph */
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GPIOB_MODER |= 1 << (1 * 2) ; /* PB1 Output [01], over default 00 */
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/* OTYPER Push-Pull by default */
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/* PB1 output default LOW at reset */
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for( ;;)
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__asm( "WFI") ; /* Wait for interrupt */
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}
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void SysTick_Handler( void) {
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GPIOB_ODR ^= 1 << 1 ; /* Toggle PB1 (User LED) */
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}
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/* end of ledtick.c */
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