diff --git a/Makefile b/Makefile
index 259f169..bba1abd 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,7 @@ LDFLAGS+=-Wl,--gc-sections -Wl,--defsym=malloc_getpagesize_P=0x1000
 #Finding Input files
 CFILES=$(shell find $(SOURCE_DIR) -name '*.c')
 #CFILES=$(notdir $(wildcard $(SOURCE_DIR)/*.c))
-SFILES=$(SOURCE_DIR)/startup.s
+SFILES=$(shell find $(SOURCE_DIR) -name '*.s')
 
 #Generate corresponding obj names
 SOBJS=$(SFILES:.s=.o)
diff --git a/src/io.c b/src/io.c.unused
similarity index 100%
rename from src/io.c
rename to src/io.c.unused
diff --git a/src/io.s b/src/io.s
new file mode 100644
index 0000000..af8d622
--- /dev/null
+++ b/src/io.s
@@ -0,0 +1,90 @@
+
+    
+//--------Local Functions ------------------ 
+//void pin_create(pin_t* pin, GPIO_TypeDef* GPIO, uint8_t pinnr)
+
+//R0: address to pin struct, R1: address to GPIO, R2: pinnr (1 byte). No return value
+pin_create:
+
+    //TODO: Implement
+
+end_pin_create:
+
+
+//bool pin_get(pin_t* pin)
+
+//R0: address to pin struct. Return value in R0 (1 byte)
+pin_get:
+
+    //TODO: Implement
+
+end_pin_get:
+
+
+//-------Global Functions-------------------
+//void io_init(void);
+.global io_init
+
+//No Parameters, No Return value
+io_init:
+
+    //convention for idermiediate labels. io_init_<whatever>
+    //TODO: Implement
+
+
+    //BL pin_create (4x)
+
+
+end_io_init:
+
+
+
+//void io_process(void)
+.global io_process
+
+//No Parameters, No Return value
+io_process:
+
+    //TODO: Implement
+
+end_io_process:
+
+
+
+//bool io_button_has_edge(uint8_t btnnumber)
+.global io_button_has_edge
+
+//R0: pin nr (1 byte), Return value in R0 (1 byte)
+io_button_has_edge:
+
+    //TODO: Implement
+
+end_io_button_has_edge:
+
+
+
+//uint16_t read_adc()
+.global read_adc
+
+//No Parameters, Return value in R0 (halfword, 2bytes)
+read_adc:
+
+    //TODO: Implement
+
+end_read_adc:
+
+
+
+//uint8_t read_switches()
+.global read_switches
+
+//No Parameters, Return value in R0 (1 byte)
+read_switches:
+
+    //TODO: Implement
+
+end_read_switches:
+
+
+
+