diff --git a/bootlib.c b/bootlib.c
new file mode 100644
--- /dev/null
+++ b/bootlib.c
@@ -0,0 +1,51 @@
+#include "stm32f0xx_hal.h"
+
+// Unset bootloader option bytes 
+void bootloader_unset(void)
+{
+    FLASH_OBProgramInitTypeDef OBParam;
+ 
+    HAL_FLASHEx_OBGetConfig(&OBParam);
+ 
+    if(OBParam.USERConfig != 0xFF)
+    {
+ 
+        OBParam.OptionType = OPTIONBYTE_USER;
+        OBParam.USERConfig = 0xFF;
+ 
+        HAL_FLASH_Unlock();
+        HAL_FLASH_OB_Unlock();
+        HAL_FLASHEx_OBErase();
+        HAL_FLASHEx_OBProgram(&OBParam);
+        HAL_FLASH_OB_Lock();
+        HAL_FLASH_OB_Launch();
+    }
+}
+
+
+// See thread: https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3a%2f%2fmy.st.com%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex_mx_stm32%2fJump%20to%20USB%20DFU%20Bootloader%20in%20startup%20code%20on%20STM32F042&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=185
+// Set option bytes to enter bootloader upon reset
+void bootloader_enter(void) {
+
+    FLASH_OBProgramInitTypeDef OBParam;
+   
+    HAL_FLASHEx_OBGetConfig(&OBParam);
+  
+    OBParam.OptionType = OPTIONBYTE_USER;
+    /*Reset NBOOT0 and BOOT_SEL,  see: RM 2.5 Boot configuration*/
+    OBParam.USERConfig = 0x77; //Sorry for magic number :)
+  
+    HAL_FLASH_Unlock();
+    HAL_FLASH_OB_Unlock();
+  
+    HAL_FLASHEx_OBErase();
+  
+    HAL_FLASHEx_OBProgram(&OBParam);
+  
+    HAL_FLASH_OB_Lock();
+    HAL_FLASH_Lock();
+  
+    HAL_FLASH_OB_Launch();
+}
+
+