[sys_time] replace SYS_TIME_RESOLUTION with SYS_TIME_FREQUENCY

sw/airborne/arch/lpc21/mcu_periph/sys_time_arch.c

@@ -105,11 +105,7 @@
 void sys_time_arch_init( void ) {
   sys_time.cpu_ticks_per_sec = PCLK / T0_PCLK_DIV;
   /* cpu ticks per desired sys_time timer step */
-  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution_sec * sys_time.cpu_ticks_per_sec + 0.5);
-
-  /* set final sys_time resolution in seconds from resolution in cpu_ticks */
-  sys_time.resolution_sec = (float)sys_time.resolution_cpu_ticks / sys_time.cpu_ticks_per_sec;
-  sys_time.ticks_per_sec = (uint32_t)(sys_time.cpu_ticks_per_sec / sys_time.resolution_cpu_ticks + 0.5);
+  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution * sys_time.cpu_ticks_per_sec + 0.5);
 
   /* setup Timer 0 to count forever  */
   /* reset & disable timer 0         */

sw/airborne/arch/sim/mcu_periph/sys_time_arch.c

@@ -31,7 +31,7 @@
 void sys_time_arch_init( void ) {
   // simulate 1us cpu ticks
   sys_time.cpu_ticks_per_sec = 1e6;
-  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution_sec * sys_time.cpu_ticks_per_sec + 0.5);
+  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution * sys_time.cpu_ticks_per_sec + 0.5);
 }
 
 void sys_tick_handler( void ) {

sw/airborne/arch/stm32/mcu_periph/sys_time_arch.c

@@ -44,11 +44,7 @@ void sys_time_arch_init( void ) {
   sys_time.cpu_ticks_per_sec = AHB_CLK;
 
   /* cpu ticks per desired sys_time timer step */
-  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution_sec * sys_time.cpu_ticks_per_sec + 0.5);
-
-  /* set final sys_time resolution in seconds from resolution in cpu_ticks */
-  sys_time.resolution_sec = (float)sys_time.resolution_cpu_ticks / sys_time.cpu_ticks_per_sec;
-  sys_time.ticks_per_sec = (uint32_t)(sys_time.cpu_ticks_per_sec / sys_time.resolution_cpu_ticks + 0.5);
+  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution * sys_time.cpu_ticks_per_sec + 0.5);
 
   /* The timer interrupt is activated on the transition from 1 to 0,
    * therefore it activates every n+1 clock ticks.

sw/airborne/mcu_periph/sys_time.c

@@ -30,9 +30,9 @@
 #include "mcu_periph/sys_time.h"
 #include "mcu.h"
 
-struct sys_time sys_time;
+PRINT_CONFIG_VAR(SYS_TIME_FREQUENCY)
 
-PRINT_CONFIG_VAR(SYS_TIME_RESOLUTION)
+struct sys_time sys_time;
 
 int sys_time_register_timer(float duration, sys_time_cb cb) {
 
@@ -72,8 +72,8 @@ void sys_time_init( void ) {
   sys_time.nb_sec_rem = 0;
   sys_time.nb_tick    = 0;
 
-  sys_time.resolution_sec = SYS_TIME_RESOLUTION;
-  sys_time.ticks_per_sec = 1.0 / sys_time.resolution_sec;
+  sys_time.ticks_per_sec = SYS_TIME_FREQUENCY;
+  sys_time.resolution = 1.0 / sys_time.ticks_per_sec;
 
   for (unsigned int i=0; i<SYS_TIME_NB_TIMER; i++) {
     sys_time.timer[i].in_use     = FALSE;

sw/airborne/mcu_periph/sys_time.h

@@ -40,12 +40,16 @@
 #define SYS_TIME_NB_TIMER 8
 #endif
 
-/** system time resolution in seconds */
-#ifndef SYS_TIME_RESOLUTION
+
+/**
+ * (Default) sys_time timer frequency in Hz.
+ * sys_time.resolution is set from this define.
+ */
+#ifndef SYS_TIME_FREQUENCY
 #if defined PERIODIC_FREQUENCY
-#define SYS_TIME_RESOLUTION ( 1./(2*PERIODIC_FREQUENCY) )
+#define SYS_TIME_FREQUENCY (2 * PERIODIC_FREQUENCY)
 #else
-#define SYS_TIME_RESOLUTION ( 1./1000. )
+#define SYS_TIME_FREQUENCY 1000
 #endif
 #endif
 
@@ -67,9 +71,9 @@ struct sys_time {
   volatile uint32_t nb_tick;      ///< SYS_TIME_TICKS since startup
   struct sys_time_timer timer[SYS_TIME_NB_TIMER];
 
-  float resolution_sec;           ///< sys_time_timer resolution in seconds
+  float resolution;               ///< sys_time_timer resolution in seconds
+  uint32_t ticks_per_sec;         ///< sys_time ticks per second (SYS_TIME_FREQUENCY)
   uint32_t resolution_cpu_ticks;  ///< sys_time_timer resolution in cpu ticks
-  uint32_t ticks_per_sec;         ///< sys_time ticks per second
   uint32_t cpu_ticks_per_sec;     ///< cpu ticks per second
 };
 
@@ -137,7 +141,7 @@ static inline uint32_t sys_time_ticks_of_usec(uint32_t usec) {
 }
 
 static inline float sec_of_sys_time_ticks(uint32_t ticks) {
-  return (float)ticks * sys_time.resolution_sec;
+  return (float)ticks * sys_time.resolution;
 }
 
 static inline uint32_t msec_of_sys_time_ticks(uint32_t ticks) {

sw/airborne/subsystems/gps.h

@@ -135,7 +135,7 @@ extern struct GpsTimeSync gps_time_sync;
 
 /**
  * Convert time in sys_time ticks to GPS time of week.
- * The resolution depends on #SYS_TIME_RESOLUTION
+ * The resolution is sys_time.resolution
  * @return GPS tow in ms
  */
 extern uint32_t gps_tow_from_sys_ticks(uint32_t sys_ticks);

sw/simulator/nps/nps_main.c

@@ -36,7 +36,7 @@
 #include "nps_flightgear.h"
 
 #include "mcu_periph/sys_time.h"
-#define SIM_DT     (SYS_TIME_RESOLUTION)
+#define SIM_DT     (1./SYS_TIME_FREQUENCY)
 #define DISPLAY_DT (1./30.)
 #define HOST_TIMEOUT_MS 40
 #define HOST_TIME_FACTOR 1.

sw/simulator/sim_ac_jsbsim.c

@@ -78,7 +78,7 @@ static void sim_init(void) {
   // main AP init (feed the sensors once before ?)
   sim_autopilot_init();
 
-  printf("sys_time resolution: %f\n", SYS_TIME_RESOLUTION);
+  printf("sys_time frequency: %f\n", SYS_TIME_FREQUENCY);
   printf("sys_time period in msec: %d\n", SYSTIME_PERIOD);
 
 }

sw/simulator/sim_ac_jsbsim.h

@@ -42,7 +42,7 @@
 #endif
 #define DT (JSBSIM_PERIOD*1e-3) ///< JSBSim timestep in seconds
 
-#define SYSTIME_PERIOD ((uint32_t)(SYS_TIME_RESOLUTION * 1000)) ///< in msec
+#define SYSTIME_PERIOD ((uint32_t)(1000. / SYS_TIME_FREQUENCY)) ///< in msec
 
 #define RAD2DEG 57.29578
 #define FT2M 0.3048