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blink.c
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blink.c
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/* blink.c -- user LED blink
** Copyright (c) 2020-2021 Renaud Fivet
*/
/* Memory locations defined by linker script */
void __StackTop( void) ; /* __StackTop points after end of stack */
void Reset_Handler( void) ; /* Entry point for execution */
/* Interrupt vector table:
* 1 Stack Pointer reset value
* 15 System Exceptions
* NN Device specific Interrupts
*/
typedef void (*isr_p)( void) ;
isr_p const isr_vector[ 2] __attribute__((section(".isr_vector"))) = {
__StackTop,
/* System Exceptions */
Reset_Handler
} ;
#define RCC ((volatile long *) 0x40021000)
#define RCC_AHBENR RCC[ 5]
#define RCC_AHBENR_IOPBEN 0x00040000 /* 18: I/O port B clock enable */
#define GPIOB ((volatile long *) 0x48000400)
#define GPIOB_MODER GPIOB[ 0]
#define GPIOB_ODR GPIOB[ 5]
void Reset_Handler( void) {
int delay ;
/* User LED ON */
RCC_AHBENR |= RCC_AHBENR_IOPBEN ; /* Enable IOPB periph */
GPIOB_MODER |= 1 << (1 * 2) ; /* PB1 Output [01], over default 00 */
/* OTYPER Push-Pull by default */
/* PB1 output default LOW at reset */
/* User LED blink */
for( ;;) {
for( delay = 1000000 ; delay ; delay--) ; /* delay between toggling */
GPIOB_ODR ^= 1 << 1 ; /* toggle PB1 (User LED) */
}
}
/* end of blink.c */