diff --git a/Makefile b/Makefile
index 67cc910..e44caea 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,8 @@
 PROJECT := main
 BUILD_DIR := bin
 
-CFILES := main.c system.c
-# CFILES += $(wildcard *.c)
+# CFILES := main.c system.c
+CFILES += $(wildcard *.c)
 OPENCM3_DIR := ./libopencm3
 
 # Check if libopencm3 is available before including anything
diff --git a/crypto.c b/crypto.c
index 6df3060..7f09ead 100644
--- a/crypto.c
+++ b/crypto.c
@@ -9,7 +9,7 @@ static uint8_t seed[32];
 
 static uint8_t signature[64];
 
-void crypto(void) {
+void crypto_demo(void) {
     crypto_eddsa_key_pair(sk, pk, seed);
     char *msg = "Hello\n";
 
diff --git a/crypto.h b/crypto.h
index 6f70f09..f93f914 100644
--- a/crypto.h
+++ b/crypto.h
@@ -1 +1,3 @@
 #pragma once
+
+void crypto_demo(void);
diff --git a/system.c b/system.c
index c1ec96e..86b3b67 100644
--- a/system.c
+++ b/system.c
@@ -4,6 +4,7 @@
 
 volatile uint64_t ticks;
 
+__attribute__((interrupt)) void sys_tick_handler(void);
 void sys_tick_handler(void) { ticks++; }
 
 uint64_t sys_ticks_get(void) { return ticks; }
diff --git a/system.h b/system.h
index 84823af..9f86a9b 100644
--- a/system.h
+++ b/system.h
@@ -1,7 +1,7 @@
 #pragma once
 #include <stdint.h>
 
-void     sys_tick_handler(void);
+// void     sys_tick_handler(void);
 uint64_t sys_get_ticks(void);
 void     sys_tick_setup(void);
 uint64_t sys_ticks_get(void);
diff --git a/uart.c b/uart.c
index 9947a18..7267a80 100644
--- a/uart.c
+++ b/uart.c
@@ -1,8 +1,9 @@
 #include <libopencm3/stm32/usart.h>
 #include <libopencm3/stm32/rcc.h>
 #include <libopencm3/stm32/gpio.h>
+#include "uart.h"
 
-static void usart_setup(void) {
+void usart_setup(void) {
     rcc_periph_clock_enable(RCC_GPIOA);
     rcc_periph_clock_enable(RCC_USART1);
 
diff --git a/uart.h b/uart.h
new file mode 100644
index 0000000..8392332
--- /dev/null
+++ b/uart.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void usart_setup(void);