diff --git a/src/main.zig b/src/main.zig
index 0fe4497..64bc6d4 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -3,7 +3,7 @@
 //! is to delete this file and start with root.zig instead.
 //const std = @import("std");
 
-const gpio = packed struct {
+const gpio_registers = packed struct {
     moder: u32,
     otyper: u32,
     ospeedr: u32,
@@ -18,6 +18,34 @@ const gpio = packed struct {
     ascr: u32,
 };
 
+const gpio = struct {
+    port: *gpio_registers,
+
+    const mode = enum {
+        input,
+        output,
+        alternate,
+        analog,
+    };
+
+    pub fn set_mode(self: gpio, pin: u4, m: mode) void {
+        self.port.moder &= ~(@as(u32, 0x3) << (2 * pin));
+
+        const mask: u32 = switch (m) {
+            .input => 0,
+            .output => 1,
+            .alternate => 2,
+            .analog => 3
+        };
+
+        self.port.moder |= mask << (2 * pin);
+    }
+
+    pub fn toggle(self: gpio, pin: u4) void {
+        self.port.odr ^= @as(u32, 1) << pin;
+    }
+};
+
 const cpu = struct {
     pub fn interrupt_disable() void {
         asm volatile("cpsid i");
@@ -28,18 +56,17 @@ const cpu = struct {
     }
 };
 
-const gpioa: *gpio = @ptrFromInt(0x48000000);
+const gpioa = gpio { .port = @ptrFromInt(0x48000000) };
 const rcc: *[39]u32 = @ptrFromInt(0x40021000);
 
 export fn _start() callconv(.C) noreturn {
     cpu.interrupt_disable();
 
     rcc[19] |= 1; // gpioaen
-    gpioa.moder &= ~@as(u32, 0x3 << (5 * 2));
-    gpioa.moder |= (1 << (5 * 2));
+    gpioa.set_mode(5, .output);
 
     while (true) {
-        gpioa.odr ^= (1 << 5);
+        gpioa.toggle(5);
     }
 }