1 files changed, 37 insertions, 1 deletions
diff --git a/src/main.zig b/src/main.zig
index de602dd..0fe4497 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -3,8 +3,44 @@
 //! is to delete this file and start with root.zig instead.
 //const std = @import("std");
 
+const gpio = packed struct {
+    moder: u32,
+    otyper: u32,
+    ospeedr: u32,
+    pupdr: u32,
+    idr: u32,
+    odr: u32,
+    bsrr: u32,
+    lckr: u32,
+    afrl: u32,
+    afrh: u32,
+    brr: u32,
+    ascr: u32,
+};
+
+const cpu = struct {
+    pub fn interrupt_disable() void {
+        asm volatile("cpsid i");
+    }
+
+    pub fn interrupt_enable() void {
+        asm volatile("cpsie i");
+    }
+};
+
+const gpioa: *gpio = @ptrFromInt(0x48000000);
+const rcc: *[39]u32 = @ptrFromInt(0x40021000);
+
 export fn _start() callconv(.C) noreturn {
-    while (true) {}
+    cpu.interrupt_disable();
+
+    rcc[19] |= 1; // gpioaen
+    gpioa.moder &= ~@as(u32, 0x3 << (5 * 2));
+    gpioa.moder |= (1 << (5 * 2));
+
+    while (true) {
+        gpioa.odr ^= (1 << 5);
+    }
 }
 
 export fn fault_handler() callconv(.C) void {