Function esp_idf_svc::sys::xTimerPendFunctionCallFromISR

pub unsafe extern "C" fn xTimerPendFunctionCallFromISR(
    xFunctionToPend: Option<unsafe extern "C" fn(_: *mut c_void, _: u32)>,
    pvParameter1: *mut c_void,
    ulParameter2: u32,
    pxHigherPriorityTaskWoken: *mut i32,
) -> i32

Used from application interrupt service routines to defer the execution of a function to the RTOS daemon task (the timer service task, hence this function is implemented in timers.c and is prefixed with ‘Timer’).

Ideally an interrupt service routine (ISR) is kept as short as possible, but sometimes an ISR either has a lot of processing to do, or needs to perform processing that is not deterministic. In these cases xTimerPendFunctionCallFromISR() can be used to defer processing of a function to the RTOS daemon task.

A mechanism is provided that allows the interrupt to return directly to the task that will subsequently execute the pended callback function. This allows the callback function to execute contiguously in time with the interrupt - just as if the callback had executed in the interrupt itself.

@param xFunctionToPend The function to execute from the timer service/ daemon task. The function must conform to the PendedFunction_t prototype.

@param pvParameter1 The value of the callback function’s first parameter. The parameter has a void * type to allow it to be used to pass any type. For example, unsigned longs can be cast to a void *, or the void * can be used to point to a structure.

@param ulParameter2 The value of the callback function’s second parameter.

@param pxHigherPriorityTaskWoken As mentioned above, calling this function will result in a message being sent to the timer daemon task. If the priority of the timer daemon task (which is set using configTIMER_TASK_PRIORITY in FreeRTOSConfig.h) is higher than the priority of the currently running task (the task the interrupt interrupted) then *pxHigherPriorityTaskWoken will be set to pdTRUE within xTimerPendFunctionCallFromISR(), indicating that a context switch should be requested before the interrupt exits. For that reason *pxHigherPriorityTaskWoken must be initialised to pdFALSE. See the example code below.

@return pdPASS is returned if the message was successfully sent to the timer daemon task, otherwise pdFALSE is returned.

Example usage: @verbatim

// The callback function that will execute in the context of the daemon task. // Note callback functions must all use this same prototype. void vProcessInterface( void *pvParameter1, uint32_t ulParameter2 ) { BaseType_t xInterfaceToService;

 // The interface that requires servicing is passed in the second
 // parameter.  The first parameter is not used in this case.
 xInterfaceToService = ( BaseType_t ) ulParameter2;

 // ...Perform the processing here...

}

// An ISR that receives data packets from multiple interfaces void vAnISR( void ) { BaseType_t xInterfaceToService, xHigherPriorityTaskWoken;

 // Query the hardware to determine which interface needs processing.
 xInterfaceToService = prvCheckInterfaces();

 // The actual processing is to be deferred to a task.  Request the
 // vProcessInterface() callback function is executed, passing in the
 // number of the interface that needs processing.  The interface to
 // service is passed in the second parameter.  The first parameter is
 // not used in this case.
 xHigherPriorityTaskWoken = pdFALSE;
 xTimerPendFunctionCallFromISR( vProcessInterface, NULL, ( uint32_t ) xInterfaceToService, &xHigherPriorityTaskWoken );

 // If xHigherPriorityTaskWoken is now set to pdTRUE then a context
 // switch should be requested.  The macro used is port specific and will
 // be either portYIELD_FROM_ISR() or portEND_SWITCHING_ISR() - refer to
 // the documentation page for the port being used.
 portYIELD_FROM_ISR( xHigherPriorityTaskWoken );

} @endverbatim