AVRGameboy/main.c at dev · harishun/AVRGameboy · GitHub

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// main.c — Real-time non-blocking core loop (~60 FPS tick).
//
// Owns g_context's storage and drives the hierarchical state machine:
// each frame, service input, run any pending screen transition, then
// Update()/Draw() whichever screen is active, then service audio and
// backlight. Pacing comes entirely from systemGetTimeMs() deltas -- no
// _delay_ms() anywhere in this loop.

#include <avr/io.h>
#include <avr/interrupt.h>

#include "context.h"
#include "system.h"
#include "backlight.h"
#include "display.h"
#include "input.h"
#include "audio.h"
#include "boot.h"
#include "menu.h"
#include "snake.h"
#include "tetris.h"
#include "bricks.h"
#include "launcher.h"
#include "storage.h"

// Global user name for high scores
char g_playerName[4] = "AAA";
bool g_isContinuing = false;

// Define the global system context
SystemContext g_context; // storage for the extern declared in context.h

#define FRAME_INTERVAL_MS 16u // ~60 FPS (16.67ms rounded down)

// ----------------------------------------------------------------------------
// Screen Management
// ----------------------------------------------------------------------------

static void handleScreenTransition(void) {
    if (g_context.nextScreen == g_context.screen && g_context.screenEntered) {
        return;
    }

    g_context.screen        = g_context.nextScreen;
    g_context.screenEntered = true;

    switch (g_context.screen) {
        case SCREEN_BOOT:        bootEnter(); break;
        case SCREEN_MENU:        menuEnter(); break;
        case SCREEN_GAME_LAUNCHER: launcherEnter(); break;
        case SCREEN_NAME_ENTRY:  NameEntry_Enter(); break;
        case SCREEN_GAME_SNAKE:  snakeEnter(); break;
        case SCREEN_GAME_TETRIS: tetrisEnter(); break;
        case SCREEN_GAME_BRICKS: bricksEnter(); break;
        case SCREEN_SETTINGS:    settingsEnter(); break;
    }
}

static void updateCurrentScreen(uint32_t nowMs, uint16_t deltaMs) {
    switch (g_context.screen) {
        case SCREEN_BOOT:        bootUpdate(nowMs, deltaMs); break;
        case SCREEN_MENU:        menuUpdate(nowMs, deltaMs); break;
        case SCREEN_GAME_LAUNCHER: launcherUpdate(nowMs, deltaMs); break;
        case SCREEN_NAME_ENTRY:  NameEntry_Update(nowMs, deltaMs); break;
        case SCREEN_GAME_SNAKE:  snakeUpdate(nowMs, deltaMs); break;
        case SCREEN_GAME_TETRIS: tetrisUpdate(nowMs, deltaMs); break;
        case SCREEN_GAME_BRICKS: bricksUpdate(nowMs, deltaMs); break;
        case SCREEN_SETTINGS:    settingsUpdate(nowMs, deltaMs); break;
    }
}

static void drawCurrentScreen(void) {
    switch (g_context.screen) {
        case SCREEN_BOOT:        bootDraw(); break;
        case SCREEN_MENU:        menuDraw(); break;
        case SCREEN_GAME_LAUNCHER: launcherDraw(); break;
        case SCREEN_NAME_ENTRY:  NameEntry_Draw(); break;
        case SCREEN_GAME_SNAKE:  snakeDraw(); break;
        case SCREEN_GAME_TETRIS: tetrisDraw(); break;
        case SCREEN_GAME_BRICKS: bricksDraw(); break;
        case SCREEN_SETTINGS:    settingsDraw(); break;
    }
}

int main(void) {
    contextInit();
    systemInit();   // Timer0 1ms tick
    backlightInit();
    inputInit();
    displayInit();
    audioInit();     // Timer1 audio PWM
    storageInit();

    sei();

    g_context.lastTickMs = systemGetTimeMs();

    for (;;) {
        uint32_t nowMs   = systemGetTimeMs();
        uint32_t elapsed = nowMs - g_context.lastTickMs;

        if (elapsed < FRAME_INTERVAL_MS) {
            continue; // non-blocking: just re-poll the clock, no _delay_ms
        }

        g_context.deltaMs    = (uint16_t)elapsed;
        g_context.lastTickMs = nowMs;

        inputUpdate(nowMs);
        handleScreenTransition();
        updateCurrentScreen(nowMs, g_context.deltaMs);
        drawCurrentScreen();
        audioUpdate(nowMs);

        backlightSetBrightness(g_context.settings.brightness);
        backlightUpdate(nowMs);
        audioSetVolume(g_context.settings.volume);
    }

    return 0;
}