diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -40,6 +40,8 @@ SRC+=system_stm32l1xx.c
 SRC+=stm32l100c_discovery.c
 SRC+=ssd1306.c
 SRC+=eeprom_min.c
+SRC+=gpio.c
+SRC+=spi.c
 SRC+=stringhelpers.c
 
 # Discovery Source Files