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72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
2 years ago
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////////////////////////////////////////////////////////////////
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// NOTE:
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// This file contains code that intentionally CORRUPTS and
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// eventually overflows the stack as explained in the
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// Lesson-10 video.
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#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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unsigned fact(unsigned n); // prototype
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int main(void) {
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unsigned volatile x;
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x = fact(0U);
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x = 2U + 3U*fact(1U);
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x = fact(9U); // <== corrupts and overflows the stack!
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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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while (1) { // endless loop
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GPIOA_BSRR_R = (1U << LD4_PIN); // turn LD4 on
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delay(500000);
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GPIOA_BSRR_R = (1U << (LD4_PIN + 16U)); // turn LD4 off
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delay(250000);
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}
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//return 0; // unreachable code
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}
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unsigned fact(unsigned n) {
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// 0! = 1
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// n! = n*(n-1)! for n > 0
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unsigned foo[6];
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foo[n] = n;
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if (n == 0U) {
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return 1U;
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}
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else {
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return foo[n] * fact(n - 1U);
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}
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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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