Espressif ESP32-S2 Programming Manual page 938

Chapter 2. API Reference
* // key is pressed, an LCD back-light
* // without a key being pressed, then the LCD back-light
* // this case, the timer
* // the xTimerReset() function, the key press event handler
* // service routine.
*
* // The callback function assigned to the one-shot
* // parameter
* void vBacklightTimerCallback( TimerHandle_t pxTimer )
* {
* // The timer expired, therefore
* // was pressed.
* vSetBacklightState( BACKLIGHT_OFF );
* }
*
* // The key press interrupt service
* void vKeyPressEventInterruptHandler( void )
* {
* BaseType_t xHigherPriorityTaskWoken
*
* // Ensure the LCD back-light
* // responsible
* // key inactivity.
* // call FreeRTOS API functions that end
* vSetBacklightState( BACKLIGHT_ON );
*
* // xTimerStartFromISR()
* // as both cause the timer to re-calculate its expiry
* // xHigherPriorityTaskWoken was initialised to pdFALSE when it was
* // declared
* if( xTimerStartFromISR( xBacklightTimer, &xHigherPriorityTaskWoken )
pdPASS )
→
* {
* // The start command was
* // action
* }
*
* // Perform the rest of the key processing
*
* // If xHigherPriorityTaskWoken equals pdTRUE, then a context switch
* // should be
* // from inside
* // compiler.
* // actual syntax
* if( xHigherPriorityTaskWoken
* {
* // Call the interrupt safe
* // depends on the FreeRTOS port being
* }
* }
*
Return pdFAIL will be returned if the start command could not be sent to the timer command queue. pdPASS
will be returned if the command was successfully sent to the timer command queue. When the command
is actually processed will depend on the priority of the timer service/daemon task relative to other tasks in
the system, although the timers expiry time is relative to when xTimerStartFromISR() is actually called.
The timer service/daemon task priority is set by the configTIMER_TASK_PRIORITY configuration
constant.
Parameters
• xTimer: The handle of the timer being started/restarted.
• pxHigherPriorityTaskWoken: The timer service/daemon task spends most of its time in
Espressif Systems
is a one-shot timer,
is not used.
Switch off the LCD
for turning the back-light off after
This is an interrupt service routine so can only
or xTimerResetFromISR() could be called here
(in this function).
here.
performed. The syntax required to perform a context switch
an ISR varies
Inspect the demos
required.
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is switched on.
and unlike the example given
timer.
5 seconds must have passed since a key
back-light.
routine.
= pdFALSE;
is on, then restart the timer that
in "FromISR".
not executed successfully.
here.
from port to port, and from
for the port you are using to find the
!= pdFALSE )
yield function here (actual function
used).
927
(continued from previous page)
If 5 seconds pass
is switched off.
is an interrupt
In this case the
is
5 seconds of
time.
!=␣
Take appropriate
compiler to
Release v4.4
In
for