diff --git a/eepy-sys/src/syscall/mod.rs b/eepy-sys/src/syscall/mod.rs
index a6bfd6d..96c22ca 100644
--- a/eepy-sys/src/syscall/mod.rs
+++ b/eepy-sys/src/syscall/mod.rs
@@ -1,24 +1,82 @@
+#[repr(u8)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum SyscallNumber {
+    Misc = 0,
+    Image = 1,
+    Input = 2,
+    Usb = 3,
+}
+
+impl TryFrom<u8> for SyscallNumber {
+    type Error = ();
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            x if x == SyscallNumber::Misc as u8 => Ok(SyscallNumber::Misc),
+            x if x == SyscallNumber::Image as u8 => Ok(SyscallNumber::Image),
+            x if x == SyscallNumber::Input as u8 => Ok(SyscallNumber::Input),
+            x if x == SyscallNumber::Usb as u8 => Ok(SyscallNumber::Usb),
+            _ => Err(()),
+        }
+    }
+}
+
+#[repr(usize)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum MiscSyscall {
+    GetSerial = 0,
+}
+
+impl TryFrom<usize> for MiscSyscall {
+    type Error = ();
+
+    fn try_from(value: usize) -> Result<Self, Self::Error> {
+        match value {
+            x if x == MiscSyscall::GetSerial as usize => Ok(MiscSyscall::GetSerial),
+            _ => Err(()),
+        }
+    }
+}
+
+
 /// Perform a raw system call.
 #[macro_export]
 macro_rules! syscall {
     (
         $syscall_num:expr,
-        $( out $r0out:ident )? $( in $r0in:expr )?,
-        $( out $r1out:ident )? $( in $r1in:expr )?,
-        $( out $r2out:ident )? $( in $r2in:expr )?,
-        $( out $r3out:ident )? $( in $r3in:expr )?,
+        $( out $r0out:ident )? $( in $r0in:expr )? $(,
+            $( out $r1out:ident )? $( in $r1in:expr )? $(,
+                $( out $r2out:ident )? $( in $r2in:expr )? $(,
+                    $( out $r3out:ident )? $( in $r3in:expr )? $(,)?
+                )?
+            )?
+        )?
     ) => {
-        asm!(
+        ::core::arch::asm!(
             "svc #{syscall_num}",
-            $( in("r0") $r0in, )?
+            $( in("r0") $r0in as usize, )?
             $( lateout("r0") $r0out, )?
-            $( in("r1") $r1in, )?
-            $( lateout("r1") $r1out, )?
-            $( in("r2") $r2in, )?
-            $( lateout("r2") $r2out, )?
-            $( in("r3") $r3in, )?
-            $( lateout("r3") $r3out, )?
-            syscall_num = const $syscall_num,
-        );
+            $(
+                $( in("r1") $r1in as usize, )?
+                $( lateout("r1") $r1out, )?
+                $(
+                    $( in("r2") $r2in as usize, )?
+                    $( lateout("r2") $r2out, )?
+                    $(
+                        $( in("r3") $r3in as usize, )?
+                        $( lateout("r3") $r3out, )?
+                    )?
+                )?
+            )?
+            syscall_num = const $syscall_num as u8,
+        )
     }
 }
+
+pub fn get_serial() -> &'static str {
+    let mut ptr: *const [u8; 16];
+    unsafe { syscall!(SyscallNumber::Misc, out ptr in MiscSyscall::GetSerial) };
+    unsafe { core::str::from_utf8_unchecked(&*ptr) }
+}
\ No newline at end of file
diff --git a/eepy/src/main.rs b/eepy/src/main.rs
index b5d007c..5fc6085 100644
--- a/eepy/src/main.rs
+++ b/eepy/src/main.rs
@@ -15,7 +15,7 @@ use defmt_rtt as _;
 
 use core::cell::RefCell;
 use critical_section::Mutex;
-use defmt::{debug, info, trace, warn};
+use defmt::{debug, info, println, trace, warn};
 use embedded_hal::delay::DelayNs;
 use embedded_hal::digital::OutputPin;
 use embedded_hal::i2c::I2c;
@@ -39,7 +39,7 @@ use fw16_epd_bsp::hal::timer::{Alarm, Alarm0};
 use fw16_epd_bsp::pac::I2C0;
 use fw16_epd_bsp::pac::interrupt;
 use eepy_gui::draw_target::EpdDrawTarget;
-use eepy_sys::{syscall as do_syscall, Event, RefreshBlockMode, SafeOption, TouchEvent, TouchEventType};
+use eepy_sys::{Event, RefreshBlockMode, SafeOption, TouchEvent, TouchEventType};
 use tp370pgh01::rp2040::{Rp2040PervasiveSpiDelays, IoPin};
 use tp370pgh01::{Tp370pgh01, IMAGE_BYTES};
 use crate::ringbuffer::RingBuffer;
@@ -329,20 +329,7 @@ fn main() -> ! {
     }*/
 
     // Test syscall
-    unsafe {
-        let mut r0: usize;
-        let mut r1: usize;
-        let mut r2: usize;
-        let mut r3: usize;
-        do_syscall!(
-            31,
-            out r0 in 0,
-            out r1 in 1,
-            out r2 in 2,
-            out r3 in 3,
-        );
-        debug!("{} {} {} {}", r0, r1, r2, r3);
-    }
+    println!("{}", eepy_sys::syscall::get_serial());
 
     let draw_target = EpdDrawTarget::new(write_image, refresh);
     gui::gui_main(draw_target);
diff --git a/eepy/src/syscall.rs b/eepy/src/syscall.rs
index 32a8413..db3dd19 100644
--- a/eepy/src/syscall.rs
+++ b/eepy/src/syscall.rs
@@ -1,6 +1,9 @@
 use core::arch::{asm, global_asm};
 use cortex_m_rt::exception;
 use defmt::debug;
+use defmt::export::panic;
+use eepy_sys::syscall::{MiscSyscall, SyscallNumber};
+use crate::SERIAL_NUMBER;
 
 global_asm!(include_str!("syscall.s"));
 
@@ -18,11 +21,16 @@ global_asm!(include_str!("syscall.s"));
 extern "C" fn syscall(sp: *mut usize) {
     // Stack contains R0, R1, R2, R3, R12, LR, ReturnAddress, xPSR
     let stack_values = unsafe { core::slice::from_raw_parts_mut(sp, 8) };
-    let svc_operand = unsafe { (stack_values[6] as *const u8).sub(2).read() };
-    debug!("{:x}", svc_operand);
+    let syscall_num = unsafe { (stack_values[6] as *const u8).sub(2).read() };
 
-    // Increase the value of R0-R3 by 1
-    for i in 0..4 {
-        stack_values[i] += 1;
+    match SyscallNumber::try_from(syscall_num) {
+        Ok(SyscallNumber::Misc) => match MiscSyscall::try_from(stack_values[0]) {
+            Ok(MiscSyscall::GetSerial) => {
+                let serial = SERIAL_NUMBER.get().unwrap();
+                stack_values[0] = (&raw const *serial) as usize;
+            },
+            _ => panic!("illegal syscall"),
+        },
+        _ => panic!("illegal syscall"),
     }
 }
\ No newline at end of file