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58 lines
1.7 KiB
C
58 lines
1.7 KiB
C
#include "stm32c031.h"
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#include "delay.h"
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// LED marked "LD4" on the NUCLEO-C031C6 board
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#define LD4_PIN 5U
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// external LED to be inserted between GND (short leg) and
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// D12 (longer leg) on the CN9 connector
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#define LD5_PIN 6U
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int *swap(int *x, int *y);
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int *swap(int *x, int *y) {
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static int tmp[2];
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tmp[0] = *x;
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tmp[1] = *y;
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*x = tmp[1];
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*y = tmp[0];
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return tmp;
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}
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int main(void) {
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// enable GPIOA clock port for the LEDs
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RCC_IOPENR_R |= (1U << 0U);
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// NUCLEO-C031C6 board has LED LD4 on GPIOA pin LD4_PIN
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// and external LED LD5 on GPIO LD5_PIN
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// set the LED pins as push-pull output, no pull-up, pull-down
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GPIOA_MODER_R &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));
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GPIOA_MODER_R |= ((1U << 2U*LD4_PIN) | (1U << 2U*LD5_PIN));
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GPIOA_OTYPER_R &= ~((1U << LD4_PIN) | (1U << LD5_PIN));
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GPIOA_OSPEEDR_R &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));
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GPIOA_OSPEEDR_R |= ((1U << 2U*LD4_PIN) | (1U << 2U*LD5_PIN));
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GPIOA_PUPDR_R &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));
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GPIOA_BSRR_R = (1U << LD5_PIN); // turn LD5 on
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int x = 1000000;
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int y = 1000000/2;
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while (1) { // endless loop
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int *p = swap(&x, &y);
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GPIOA_BSRR_R = (1U << LD4_PIN); // turn LD4 on
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delay(p[0]);
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GPIOA_BSRR_R = (1U << (LD4_PIN + 16U)); // turn LD4 off
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delay(p[1]);
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}
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//return 0; // unreachable code
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}
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////////////////////////////////////////////////////////////////
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// NOTE: the file main_swap.c in the project directory contains
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// the code with the swap() function to illustrate the use of
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// pointer parameters in Lesson-10 video.
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// To use the other file, simply copy main_swap.c to main.c.
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