-#define AO_STM_NVIC_HIGH_PRIORITY 4
-#define AO_STM_NVIC_CLOCK_PRIORITY 6
-#define AO_STM_NVIC_MED_PRIORITY 8
-#define AO_STM_NVIC_LOW_PRIORITY 10
+/* The stm32l implements only 4 bits of the priority fields */
+
+#define AO_STM_NVIC_HIGH_PRIORITY 0x40
+#define AO_STM_NVIC_MED_PRIORITY 0x80
+#define AO_STM_NVIC_LOW_PRIORITY 0xC0
+#define AO_STM_NVIC_CLOCK_PRIORITY 0xf0