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Every real-time simulation requires a clock to which its tasks can be synchronized. By default, a Trick simulation uses the local system clock, by calling gettimeofday(). When simulations running on different computers need to cooperate they need to be synchronized to the same clock. So, sometimes we want our simulation to synchronize a to an external clock rather than the local one. The Trick::Clock
base class provides a way to create an interface between an external time source, and a real-time Trick simulation.
The Trick::Clock class is declared in trick/Clock.hh
. Deriving a new clock interface class from it requires the following three member functions to be implemented.
int Trick::Clock::clock_init();
set_global_clock()
and return 0.long long Trick::Clock::wall_clock_time()
int Trick::Clock::clock_stop()
By default, Trick uses a derivative of Trick::Clock
called Trick::GetTimeOfDayClock
.
Suppose we've derived a new class CuckooClock
from Trick::Clock
, and have created an instance of it:
chalet.my_clock = new CuckooClock();
In our simulation's S_define file, we could change the real-time scheduler's clock from the default Trick::GetTimeOfDayClock
to our new CuckooClock
using real_time_change_clock()
, declared in trick/realtimesync_proto.h
.
void create_connections() {
chalet.my_clock = new CuckooClock();
real_time_change_clock(chalet.my_clock);
}
We could also change the Trick::Clock
in our input file as follows:
trick.real_time_change_clock(chalet.my_clock)
The following code is an example implementation of a Trick::Clock, called TPROCTEClock. It provides an interface between Trick's real-time job scheduler and Spectracom's TPRO IRIG-B clock board. This is one of many available time sources that one might use. Note that driver support for timing cards, like the "tpro.h" and "tsync.h" files below, must be acquired from the card's vendor.
/*
PURPOSE: ( TPRO CTE Clock )
*/
#ifndef TPROCTECLOCK_HH
#define TPROCTECLOCK_HH
#include <string>
#include "trick/Clock.hh"
#ifdef _TPRO_CTE
extern "C" {
#include "tpro.h"
#include "tsync.h"
}
#endif
class TPROCTEClock : public Trick::Clock {
public:
TPROCTEClock() ;
~TPROCTEClock() ;
int clock_init() ;
long long wall_clock_time() ;
int clock_stop() ;
std::string dev_name ;
private:
#ifdef _TPRO_CTE
TPRO_BoardObj *pBoard ; /* ** board handle */
#endif
} ;
#endif
Here, we initialize the timing card by opening the device file, getting a device handle. Then we wait for for it to be available. If an error occurs, return a non-zero error code, otherwise we call set_global_clock()
and return 0.
int TPROCTEClock::clock_init() {
#ifdef _TPRO_CTE
unsigned char rv;
/* Open the TPRO/TSAT device */
rv = TPRO_open(&pBoard, (char *)dev_name.c_str());
/* If unable to open the TPRO/TSAT device... */
if (rv != TPRO_SUCCESS) {
printf (" Could Not Open '%s'!! [%d]\n", dev_name.c_str(), rv);
return (1);
}
/* Wait until this handle is the first user of the device. */
if (TPRO_setPropDelayCorr(pBoard, NULL) != TPRO_SUCCESS) {
printf(" Waiting to become first user...\n");
while (TPRO_setPropDelayCorr(pBoard, NULL) != TPRO_SUCCESS);
}
set_global_clock() ;
return 0 ;
#else
printf("ERROR: Not configured for TPRO CTE card.");
return -1 ;
#endif
}
In this function, we get the time from the timing card, and convert it to microseconds before returning it. If the attempt to get the time fails, we return 0.
long long TPROCTEClock::wall_clock_time() {
#ifdef _TPRO_CTE
TSYNC_HWTimeSecondsObj hwTime;
/* Send Get Seconds Time message */
TSYNC_ERROR err = TSYNC_HW_getTimeSec(pBoard, &hwTime);
if (err != TSYNC_SUCCESS) {
printf(" Error: %s.\n", tsync_strerror(err));
return 0;
}
/* If sucessful convert the TPRO time to microsconds. */.
return hwTime.time.seconds * 1000000LL + (hwTime.time.ns /1000);
#else
printf("ERROR: Not configured for TPRO CTE card.");
return 0 ;
#endif
}
This function simply closes the handle to the device, and returns 0.
int TPROCTEClock::clock_stop() {
#ifdef _TPRO_CTE
unsigned char rv ;
rv = TPRO_close(pBoard);
/* If unable to close the TPRO/TSAT device... */
if (rv != TPRO_SUCCESS) {
printf (" Could Not Close Board!! [%d]\n", rv);
}
#endif
return 0 ;
}
Trick::Clock is a class for creating interfaces between timing hardware, or other time sources and Trick's realtime synchronization subsystem. It does not maintain the simulation time. That's maintained by the Trick Executive.
What you may be looking for is the function
double exec_get_sim_time(void) ;
defined in exec_proto.h
.
Continue to Realtime Timer