Continue 78K0R development.

[freertos] / Demo / NEC_78K0R_IAR / ButtonTask.c

diff --git a/Demo/NEC_78K0R_IAR/ButtonTask.c b/Demo/NEC_78K0R_IAR/ButtonTask.c
index a15202cd86f38bff3be8955d415e022162d2a217..c5d38acdbf3c9c43f30c4f36028f9b3774ee4749 100644 (file)
--- a/Demo/NEC_78K0R_IAR/ButtonTask.c
+++ b/Demo/NEC_78K0R_IAR/ButtonTask.c
@@ -47,35 +47,73 @@
        licensing and training services.\r
 */\r
 \r
+/*\r
+ * This file defines the button push task and ISR as described at the top of\r
+ * main.c.  The ISR is called from a wrapper function defined in ButtonISR.s26.\r
+ */\r
+\r
+/* Kernel includes. */\r
 #include "FreeRTOS.h"\r
 #include "task.h"\r
 #include "semphr.h"\r
 \r
-static xSemaphoreHandle xButtonSemaphore;\r
+/* The LED output used by the button push task. */\r
+#define butLED1   P7_bit.no7\r
+\r
+/* A short delay used for button debouncing. */\r
+#define butDEBOUNCE_DELAY      ( 200 / portTICK_RATE_MS )\r
 \r
-#define LED01   P7_bit.no7\r
+/* The semaphore used to synchronise the button push task with the interrupt. */\r
+static xSemaphoreHandle xButtonSemaphore;\r
 \r
+/*\r
+ * The definition of the button task itself.  See the comments at the top of\r
+ * main.c.\r
+ */\r
 void vButtonTask( void *pvParameters )\r
 {\r
+       /* Ensure the semaphore is created before it gets used. */\r
        vSemaphoreCreateBinary( xButtonSemaphore );\r
 \r
        for( ;; )\r
        {\r
+               /* Block on the semaphore to wait for an interrupt event.  The semaphore\r
+               is 'given' from vButtonISRHandler() below.  Using portMAX_DELAY as the\r
+               block time will cause the task to block indefinitely provided\r
+               INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. */\r
                xSemaphoreTake( xButtonSemaphore, portMAX_DELAY );\r
-               LED01 = !LED01;\r
+\r
+               /* The button must have been pushed for this line to be executed.\r
+               Simply toggle the LED. */\r
+               butLED1 = !butLED1;\r
                \r
-               vTaskDelay( 200 / portTICK_RATE_MS );\r
+               /* Wait a short time then clear any pending button pushes as a crude\r
+               method of debouncing the switch.  xSemaphoreTake() uses a block time of\r
+               zero this time so it returns immediately rather than waiting for the\r
+               interrupt to occur. */\r
+               vTaskDelay( butDEBOUNCE_DELAY );\r
                xSemaphoreTake( xButtonSemaphore, 0 );\r
        }\r
 }\r
 /*-----------------------------------------------------------*/\r
 \r
+/*\r
+ * The C portion of the interrupt handler.  Interrupts are triggered by pushing\r
+ * the button on the target board.  This interrupt can cause a context switch\r
+ * so has an assembly file wrapper defined within ButtonISR.s26.\r
+ */\r
 void vButtonISRHandler( void )\r
 {\r
 short sHigherPriorityTaskWoken = pdFALSE;\r
 \r
+       /* 'Give' the semaphore to unblock the button task. */\r
        xSemaphoreGiveFromISR( xButtonSemaphore, &sHigherPriorityTaskWoken );\r
        \r
+       /* If giving the semaphore unblocked a task, and the unblocked task has a\r
+       priority that is higher than the currently running task, then\r
+       sHigherPriorityTaskWoken will have been set to pdTRUE.  Passing a pdTRUE\r
+       value to portYIELD_FROM_ISR() will cause this interrupt to return directly\r
+       to the higher priority unblocked task. */\r
        portYIELD_FROM_ISR( sHigherPriorityTaskWoken );\r
 }\r
 /*-----------------------------------------------------------*/\r