[sys_time] if PERIODIC_FREQUENCY is defined, set default SYS_TIME_RESOLUTION to twice that

sw/airborne/mcu_periph/sys_time.c

@@ -32,6 +32,8 @@
 
 struct sys_time sys_time;
 
+PRINT_CONFIG_VAR(SYS_TIME_RESOLUTION)
+
 int sys_time_register_timer(float duration, sys_time_cb cb) {
 
   uint32_t start_time = sys_time.nb_tick;

sw/airborne/mcu_periph/sys_time.h

@@ -103,8 +103,12 @@ static inline bool_t sys_time_check_and_ack_timer(tid_t id) {
 
 /** system time resolution in seconds */
 #ifndef SYS_TIME_RESOLUTION
+#if defined PERIODIC_FREQUENCY
+#define SYS_TIME_RESOLUTION ( 1./(2*PERIODIC_FREQUENCY) )
+#else
 #define SYS_TIME_RESOLUTION ( 1./1024. )
 #endif
+#endif
 #define SYS_TIME_RESOLUTION_CPU_TICKS CPU_TICKS_OF_SEC(SYS_TIME_RESOLUTION)
 
 #define SYS_TIME_TICKS_OF_SEC(s) (uint32_t)((s) / SYS_TIME_RESOLUTION + 0.5)