STM Vianocna ozdoba

/**
  ******************************************************************************
  * @file    main.c
  * @author  Ac6
  * @version V1.0
  * @date    01-December-2013
  * @brief   Default main function.
  ******************************************************************************
*/

#include "stm32f4xx.h"

/* Memory mapping for registers */
static volatile uint32_t * const gpiob  = (volatile uint32_t *) 0x40020400;
static volatile uint32_t * const gpioc  = (volatile uint32_t *) 0x40020800;
static volatile uint32_t * const rcc    = (volatile uint32_t *) 0x40023800;
static volatile uint32_t * const systick= (volatile uint32_t *) 0xe000e010;

/* Global variables */
// Input timer, and led update counter
static volatile uint32_t inputCounter = 0UL, timerCounter = 0Ul;

/* Setup method */
static void setup(void)
{
    /*-Setup-SysTick-----------------------------------------------------------*/
    // Set SysTick frequency
    systick[1] = (SystemCoreClock / 1000000) - 0x00000001;

    // Set SysTick interrupt priority
    NVIC_SetPriority(SysTick_IRQn, 0x0f);

    // Clear counter
    systick[2] = 0x00000000;

    // Enable and configure
    systick[0] = 0x00000007;

    /*-Setup-GPIO-clocks-------------------------------------------------------*/
    // Enable AHB1 -> GPIOB, GPIOC
    rcc[12] |= 0x00000006;

    /*-Setup-GPIOB-(leds)------------------------------------------------------*/
    // Output mode - 0x01
    gpiob[0] &= ~0x3000c003;
    gpiob[0] |=  0x10004001;

    // Push pull - 0x0
    gpiob[1] &= 0x00004081;

    // Speed fast - 0x02
    gpiob[2] &= ~0x3000c003;
    gpiob[2] |=  0x20008002;

    // No pull - 0x00
    gpiob[3] &= ~0x3000c003;

    /*-Setup-GPIOC-(button)----------------------------------------------------*/
    // Input mode - 0x00
    gpioc[0] &= ~0x0c000000;

    // Pull down - 0x02
    gpioc[3] &= ~0x0c000000;
    gpioc[3] |=  0x08000000;
}

/* Update method  */
static void update(void)
{
    /* Stores the state of the operation of the MCU
     *
     * Bits usage:
     * +---+   +-+   +-----+
     * |7 6| 5 |4| 3 |2 1 0|
     * +---+   +-+   +-----+
     *   |      |       |
     *   |      |       +---> [0x07] Mode of operation:   {0}  : Off
     *   |      |                                       {1,2,3}: A single led is on
     *   |      |                                        {4,5} : Time based modes - led is getting toggled
     *   |      |                                                  Also uses bits 6 and 7 to store state
     *   |      |
     *   |      +-----------> [0x10] Queue update: If this bit is set, MCU will update PORTB during next cycle (when button is pressed)
     *   |
     *   +------------------> [0xc0] Mode state: Only used in time based modes, stores which led is on and which to turn on next
     *
     * Initial value: 0x11 - queue update + mode 1
     */
    static uint8_t state = 0x11;

    // If button is pressed and input isn't disabled
    if((gpioc[4] & 0x00002000) && !inputCounter) {
        // Toggle to next mode
        ++state;

        // Loop modes
        if((state & 0x0f) > 0x05)
            state = 0x00;

        // Queue update
        state |= 0x10;

        // Add 500ms input delay
        inputCounter = 5e5;
    }

    // If update is queued, or we are in a time based mode and we should update
    if((state & 0x10) || ((state & 0x04) && !timerCounter)) {
        // Port output mask
        uint32_t outputMask = 0x00000000;

        // If in a time-based mode
        if(state & 0x04) {
            // Add delay
            timerCounter = state & 0x01 ? 1e5 : 3e5;

            // Last two bits of the state
            uint8_t modeState = state >> 6;

            // Turn on a single led based on modeState
            outputMask = 0x01 << (7 * modeState);

            // Increase modeState
            if(++modeState > 2)
                modeState = 0;

            // Store modeState back to state
            state = (state & 0x3f) | (modeState << 6);
        }
        // If in a static mode
        else {
            switch(state & 0x03) {
            case 0x01:
                // Green
                outputMask = 0x00000001;
                break;

            case 0x02:
                // Blue
                outputMask = 0x00000080;
                break;

            case 0x03:
                // Red
                outputMask = 0x00004000;
                break;

            default:
                // Off
                break;
            }
        }

        // Turn on only active led
        gpiob[5] = (gpiob[5] & ~0x00004081) | outputMask;

        // Remove update if queued
        state &= ~0x10;
    }

}

/* Main method */
int main(void)
{
    // Perform setup
    setup();

    // Loop update method
    for(;;)
        update();
}

/* SysTick interrupt handler */
void SysTick_Handler(void)
{
    // Each interrupt (t=1us) decrements counters by 1

    if(inputCounter)
        inputCounter--;

    if(timerCounter)
        timerCounter--;
}