-#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 */
+
+#if AO_NONMASK_INTERRUPT
+#define AO_STM_NVIC_NONMASK_PRIORITY 0x00
+
+/* Set the basepri register to this value to mask all
+ * non-maskable priorities
+ */
+#define AO_STM_NVIC_BASEPRI_MASK 0x10
+#endif
+
+#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