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Second attempt: Improve how TimerDemo.c manages differences between the tick count and its own internal tick count, which can temporarily differ when the tick hook is called while the scheduler is suspended.

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This commit is contained in:
Richard Barry 2014-02-04 15:51:48 +00:00
parent 03f9bbda52
commit 9a8da3ff38
1 changed files with 23 additions and 9 deletions
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32
FreeRTOS/Demo/Common/Minimal/TimerDemo.c
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@ -723,12 +723,26 @@ static portTickType uxTick = ( portTickType ) -1;
callback before their expiry time, but a margin is permissible for calling callback before their expiry time, but a margin is permissible for calling
their callback after their expiry time. If exact timing is required then their callback after their expiry time. If exact timing is required then
configTIMER_TASK_PRIORITY must be set to ensure the timer service task configTIMER_TASK_PRIORITY must be set to ensure the timer service task
is the highest priority task in the system. */ is the highest priority task in the system.
This function is called from the tick hook. The tick hook is called
even when the scheduler is suspended. Therefore it is possible that the
uxTick count maintained in this function is temporarily ahead of the tick
count maintained by the kernel. When this is the case a message posted from
this function will assume a time stamp in advance of the real time stamp,
which can result in a timer being processed before this function expects it
to. For example, if the kernel's tick count was 100, and uxTick was 102,
then this function will not expect the timer to have expired until the
kernel's tick count is (102 + xBasePeriod), whereas in reality the timer
will expire when the kernel's tick count is (100 + xBasePeriod). For this
reason xMargin is used as an allowable margin for premature timer expiries
as well as late timer expiries. */
const portTickType xMargin = 5; const portTickType xMargin = 5;
#else #else
const portTickType xMargin = 2; const portTickType xMargin = 2;
#endif #endif
uxTick++; uxTick++;
if( uxTick == 0 ) if( uxTick == 0 )
@ -761,7 +775,7 @@ static portTickType uxTick = ( portTickType ) -1;
} }
} }
} }
else if( uxTick == xBasePeriod ) else if( uxTick == ( xBasePeriod - xMargin ) )
{ {
/* Neither timer should have expired yet. */ /* Neither timer should have expired yet. */
if( ( ucISRAutoReloadTimerCounter != 0 ) || ( ucISROneShotTimerCounter != 0 ) ) if( ( ucISRAutoReloadTimerCounter != 0 ) || ( ucISROneShotTimerCounter != 0 ) )
@ -780,7 +794,7 @@ static portTickType uxTick = ( portTickType ) -1;
configASSERT( xTestStatus ); configASSERT( xTestStatus );
} }
} }
else if( uxTick == ( 2 * xBasePeriod ) ) else if( uxTick == ( ( 2 * xBasePeriod ) - xMargin ) )
{ {
/* The auto reload timer will still be active, but the one shot timer /* The auto reload timer will still be active, but the one shot timer
should now have stopped - however, at this time neither of the timers should now have stopped - however, at this time neither of the timers
@ -851,7 +865,7 @@ static portTickType uxTick = ( portTickType ) -1;
a few ticks ago. */ a few ticks ago. */
xTimerStopFromISR( xISRAutoReloadTimer, NULL ); xTimerStopFromISR( xISRAutoReloadTimer, NULL );
} }
else if( uxTick == ( 4 * xBasePeriod ) ) else if( uxTick == ( 4 * ( xBasePeriod - xMargin ) ) )
{ {
/* The auto reload timer is now stopped, and the one shot timer is /* The auto reload timer is now stopped, and the one shot timer is
active, but at this time neither timer should have expired since the active, but at this time neither timer should have expired since the
@ -885,7 +899,7 @@ static portTickType uxTick = ( portTickType ) -1;
configASSERT( xTestStatus ); configASSERT( xTestStatus );
} }
} }
else if( uxTick == ( ( 8 * xBasePeriod ) + xMargin ) ) else if( uxTick == ( 8 * xBasePeriod ) )
{ {
/* The auto reload timer is now stopped, and the one shot timer has /* The auto reload timer is now stopped, and the one shot timer has
already expired and then stopped itself. Both callback counters should already expired and then stopped itself. Both callback counters should
@ -905,7 +919,7 @@ static portTickType uxTick = ( portTickType ) -1;
/* Now reset the one shot timer. */ /* Now reset the one shot timer. */
xTimerResetFromISR( xISROneShotTimer, NULL ); xTimerResetFromISR( xISROneShotTimer, NULL );
} }
else if( uxTick == ( 9 * xBasePeriod ) ) else if( uxTick == ( ( 9 * xBasePeriod ) - xMargin ) )
{ {
/* Only the one shot timer should be running, but it should not have /* Only the one shot timer should be running, but it should not have
expired since the last test. Check the callback counters have not expired since the last test. Check the callback counters have not
@ -924,7 +938,7 @@ static portTickType uxTick = ( portTickType ) -1;
xTimerResetFromISR( xISROneShotTimer, NULL ); xTimerResetFromISR( xISROneShotTimer, NULL );
} }
else if( uxTick == ( 10 * xBasePeriod ) ) else if( uxTick == ( ( 10 * xBasePeriod ) - ( 2 * xMargin ) ) )
{ {
/* Only the one shot timer should be running, but it should not have /* Only the one shot timer should be running, but it should not have
expired since the last test. Check the callback counters have not expired since the last test. Check the callback counters have not
@ -943,7 +957,7 @@ static portTickType uxTick = ( portTickType ) -1;
xTimerResetFromISR( xISROneShotTimer, NULL ); xTimerResetFromISR( xISROneShotTimer, NULL );
} }
else if( uxTick == ( 11 * xBasePeriod ) ) else if( uxTick == ( ( 11 * xBasePeriod ) - ( 3 * xMargin ) ) )
{ {
/* Only the one shot timer should be running, but it should not have /* Only the one shot timer should be running, but it should not have
expired since the last test. Check the callback counters have not expired since the last test. Check the callback counters have not
@ -962,7 +976,7 @@ static portTickType uxTick = ( portTickType ) -1;
xTimerResetFromISR( xISROneShotTimer, NULL ); xTimerResetFromISR( xISROneShotTimer, NULL );
} }
else if( uxTick == ( ( 12 * xBasePeriod ) + xMargin ) ) else if( uxTick == ( ( 12 * xBasePeriod ) - ( 2 * xMargin ) ) )
{ {
/* Only the one shot timer should have been running and this time it /* Only the one shot timer should have been running and this time it
should have expired. Check its callback count has been incremented. should have expired. Check its callback count has been incremented.