const cpu = @import("cpu.zig");
const gpio = @import("gpio.zig");
const interrupt = @import("interrupt.zig");
const timer = @import("timer.zig");

const rcc: *[39]u32 = @ptrFromInt(0x40021000);
const gpioa = gpio.gpioa;
const gpioc = gpio.gpioc;

export fn _start() callconv(.C) noreturn {
    cpu.interrupt_disable();
    interrupt.initialize();
    interrupt.register(.SVCall, svcall);
    timer.initialize(1000);
    cpu.interrupt_enable();

    rcc[19] |= 5; // gpio a and c
    gpioa.set_mode(5, .output);
    gpioc.set_mode(13, .input);

    while (true) {
        //asm volatile("svc 0");
        gpioa.toggle(5);
        const next = timer.ticks() + 1000;
        while (timer.ticks() < next) {
            asm volatile("nop");
        }
    }
}

fn svcall() void {
    const state = gpioc.read(13);
    gpioa.write(5, state);
}