#include "stm32c031xx.h"  // CMSIS-compatible interface
#include "delay.h"

// LED marked "LD4" on the NUCLEO-C031C6 board
#define LD4_PIN  5U

// external LED to be inserted between GND (short leg) and
// D12 (longer leg) on the CN9 connector
#define LD5_PIN  6U

typedef struct /* __attribute__((packed)) */ {
    uint8_t y;
    uint16_t x;
} Point;

Point p1, p2;

typedef struct {
    Point top_left;
    Point bottom_right;
} Window;

typedef struct {
     Point corners[3];
} Triangle;

Window w, w2;
Triangle t;

int main(void) {
    Point *pp;
    Window *wp;

    p1.x = sizeof(Point);
    p1.y = 0xAAU;

    w.top_left.x = 1U;
    w.bottom_right.y = 2U;

    t.corners[0].x = 1U;
    t.corners[2].y = 2U;

    p2 = p1;
    w2 = w;

    pp = &p1;
    wp = &w2;

    (*pp).x = 1U;

    (*wp).top_left = *pp;

    pp->x = 1U;
    wp->top_left = *pp;

    // enable GPIOA clock port for the LEDs
    RCC->IOPENR |= (1U << 0U);

    // NUCLEO-C031C6 board has LED LD4 on GPIOA pin LD4_PIN
    // and external LED LD5 on GPIO LD5_PIN
    // set the LED pins as push-pull output, no pull-up, pull-down
    GPIOA->MODER   &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));
    GPIOA->MODER   |=  ((1U << 2U*LD4_PIN) | (1U << 2U*LD5_PIN));
    GPIOA->OTYPER  &= ~((1U <<    LD4_PIN) | (1U <<    LD5_PIN));
    GPIOA->OSPEEDR &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));
    GPIOA->OSPEEDR |=  ((1U << 2U*LD4_PIN) | (1U << 2U*LD5_PIN));
    GPIOA->PUPDR   &= ~((3U << 2U*LD4_PIN) | (3U << 2U*LD5_PIN));

    GPIOA->BSRR = (1U << LD5_PIN); // turn LD5 on

    while (1) { // endless loop
        GPIOA->BSRR = (1U << LD4_PIN); // turn LD4 on

        delay(500000);

        GPIOA->BSRR = (1U << (LD4_PIN + 16U)); // turn LD4 off

        delay(250000);
    }
    //return 0; // unreachable code
}

//............................................................................
// function needed by the library/startup code
_Noreturn void assert_failed(char const * const module, int const id);
_Noreturn void assert_failed(char const * const module, int const id) {
    // TBD: damage control
    (void)module; // avoid the "unused parameter" compiler warning
    (void)id;     // avoid the "unused parameter" compiler warning
    NVIC_SystemReset();
}