Second attempt: Improve how TimerDemo.c manages differences between the tick count...

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2192 1d2547de-c912-0410-9cb9-b8ca96c0e9e2

diff --git a/FreeRTOS/Demo/Common/Minimal/TimerDemo.c b/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
index 27f5ed923dafa04881ba5d278020bcab447e9ae7..c4f2ba6bd3cfb77a1b9800c1eb7661eaac97b0be 100644 (file)
--- a/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
+++ b/FreeRTOS/Demo/Common/Minimal/TimerDemo.c
@@ -723,12 +723,26 @@ static portTickType uxTick = ( portTickType ) -1;
        callback before their expiry time, but a margin is permissible for calling\r
        their callback after their expiry time.  If exact timing is required then\r
        configTIMER_TASK_PRIORITY must be set to ensure the timer service task\r
-       is the highest priority task in the system. */\r
+       is the highest priority task in the system.\r
+\r
+       This function is called from the tick hook.  The tick hook is called\r
+       even when the scheduler is suspended.  Therefore it is possible that the\r
+       uxTick count maintained in this function is temporarily ahead of the tick\r
+       count maintained by the kernel.  When this is the case a message posted from\r
+       this function will assume a time stamp in advance of the real time stamp,\r
+       which can result in a timer being processed before this function expects it\r
+       to.  For example, if the kernel's tick count was 100, and uxTick was 102,\r
+       then this function will not expect the timer to have expired until the\r
+       kernel's tick count is (102 + xBasePeriod), whereas in reality the timer\r
+       will expire when the kernel's tick count is (100 + xBasePeriod).  For this\r
+       reason xMargin is used as an allowable margin for premature timer expiries\r
+       as well as late timer expiries. */\r
        const portTickType xMargin = 5;\r
 #else\r
        const portTickType xMargin = 2;\r
 #endif\r
 \r
+\r
        uxTick++;\r
 \r
        if( uxTick == 0 )\r
@@ -761,7 +775,7 @@ static portTickType uxTick = ( portTickType ) -1;
                        }\r
                }\r
        }\r
-       else if( uxTick == xBasePeriod )\r
+       else if( uxTick == ( xBasePeriod - xMargin ) )\r
        {\r
                /* Neither timer should have expired yet. */\r
                if( ( ucISRAutoReloadTimerCounter != 0 ) || ( ucISROneShotTimerCounter != 0 ) )\r
@@ -780,7 +794,7 @@ static portTickType uxTick = ( portTickType ) -1;
                        configASSERT( xTestStatus );\r
                }\r
        }\r
-       else if( uxTick == ( 2 * xBasePeriod ) )\r
+       else if( uxTick == ( ( 2 * xBasePeriod ) - xMargin ) )\r
        {\r
                /* The auto reload timer will still be active, but the one shot timer\r
                should now have stopped - however, at this time neither of the timers\r
@@ -851,7 +865,7 @@ static portTickType uxTick = ( portTickType ) -1;
                a few ticks ago. */\r
                xTimerStopFromISR( xISRAutoReloadTimer, NULL );\r
        }       \r
-       else if( uxTick == ( 4 * xBasePeriod ) )\r
+       else if( uxTick == ( 4 * ( xBasePeriod - xMargin ) ) )\r
        {\r
                /* The auto reload timer is now stopped, and the one shot timer is\r
                active, but at this time neither timer should have expired since the\r
@@ -885,7 +899,7 @@ static portTickType uxTick = ( portTickType ) -1;
                        configASSERT( xTestStatus );\r
                }\r
        }       \r
-       else if( uxTick == ( ( 8 * xBasePeriod ) + xMargin ) )\r
+       else if( uxTick == ( 8 * xBasePeriod ) )\r
        {\r
                /* The auto reload timer is now stopped, and the one shot timer has\r
                already expired and then stopped itself.  Both callback counters should\r
@@ -905,7 +919,7 @@ static portTickType uxTick = ( portTickType ) -1;
                /* Now reset the one shot timer. */\r
                xTimerResetFromISR( xISROneShotTimer, NULL );\r
        }       \r
-       else if( uxTick == ( 9 * xBasePeriod ) )\r
+       else if( uxTick == ( ( 9 * xBasePeriod ) - xMargin ) )\r
        {\r
                /* Only the one shot timer should be running, but it should not have\r
                expired since the last test.  Check the callback counters have not\r
@@ -924,7 +938,7 @@ static portTickType uxTick = ( portTickType ) -1;
                \r
                xTimerResetFromISR( xISROneShotTimer, NULL );\r
        }       \r
-       else if( uxTick == ( 10 * xBasePeriod ) )\r
+       else if( uxTick == ( ( 10 * xBasePeriod ) - ( 2 * xMargin ) ) )\r
        {\r
                /* Only the one shot timer should be running, but it should not have\r
                expired since the last test.  Check the callback counters have not\r
@@ -943,7 +957,7 @@ static portTickType uxTick = ( portTickType ) -1;
                \r
                xTimerResetFromISR( xISROneShotTimer, NULL );\r
        }\r
-       else if( uxTick == ( 11 * xBasePeriod ) )\r
+       else if( uxTick == ( ( 11 * xBasePeriod ) - ( 3 * xMargin ) ) )\r
        {\r
                /* Only the one shot timer should be running, but it should not have\r
                expired since the last test.  Check the callback counters have not\r
@@ -962,7 +976,7 @@ static portTickType uxTick = ( portTickType ) -1;
                \r
                xTimerResetFromISR( xISROneShotTimer, NULL );\r
        }       \r
-       else if( uxTick == ( ( 12 * xBasePeriod ) + xMargin ) )\r
+       else if( uxTick == ( ( 12 * xBasePeriod ) - ( 2 * xMargin ) ) )\r
        {\r
                /* Only the one shot timer should have been running and this time it\r
                should have     expired.  Check its callback count has been incremented.\r