Chapter 2. API Reference
(continued from previous page)
const TickType_t xTicksToWait = 100 / portTICK_PERIOD_MS;
// Wait a maximum of 100ms for either bit 0 or bit 4 to be set within
// the event group. Clear the bits before exiting.
uxBits = xEventGroupWaitBits(
xEventGroup, // The event group being tested.
BIT_0 | BIT_4, // The bits within the event group to wait␣
,→for.
pdTRUE, // BIT_0 and BIT_4 should be cleared before␣
,→returning.
pdFALSE, // Don't wait for both bits, either bit will␣
,→do.
xTicksToWait ); // Wait a maximum of 100ms for either bit to␣
,→be set.
if( ( uxBits & ( BIT_0 | BIT_4 ) ) == ( BIT_0 | BIT_4 ) )
{
// xEventGroupWaitBits() returned because both bits were set.
}
else if( ( uxBits & BIT_0 ) != 0 )
{
// xEventGroupWaitBits() returned because just BIT_0 was set.
}
else if( ( uxBits & BIT_4 ) != 0 )
{
// xEventGroupWaitBits() returned because just BIT_4 was set.
}
else
{
// xEventGroupWaitBits() returned because xTicksToWait ticks passed
// without either BIT_0 or BIT_4 becoming set.
}
}
Return The value of the event group at the time either the bits being waited for became set, or the block time
expired. Test the return value to know which bits were set. If xEventGroupWaitBits() returned because
its timeout expired then not all the bits being waited for will be set. If xEventGroupWaitBits() returned
because the bits it was waiting for were set then the returned value is the event group value before any
bits were automatically cleared in the case that xClearOnExit parameter was set to pdTRUE.
Parameters
• xEventGroup: The event group in which the bits are being tested. The event group must have
previously been created using a call to xEventGroupCreate().
• uxBitsToWaitFor: A bitwise value that indicates the bit or bits to test inside the event group.
For example, to wait for bit 0 and/or bit 2 set uxBitsToWaitFor to 0x05. To wait for bits 0 and/or
bit 1 and/or bit 2 set uxBitsToWaitFor to 0x07. Etc.
• xClearOnExit: If xClearOnExit is set to pdTRUE then any bits within uxBitsToWaitFor that
are set within the event group will be cleared before xEventGroupWaitBits() returns if the wait
condition was met (if the function returns for a reason other than a timeout). If xClearOnExit is set to
pdFALSE then the bits set in the event group are not altered when the call to xEventGroupWaitBits()
returns.
• xWaitForAllBits: If xWaitForAllBits is set to pdTRUE then xEventGroupWaitBits() will re-
turn when either all the bits in uxBitsToWaitFor are set or the specified block time expires. If
xWaitForAllBits is set to pdFALSE then xEventGroupWaitBits() will return when any one of the
bits set in uxBitsToWaitFor is set or the specified block time expires. The block time is specified by
the xTicksToWait parameter.
• xTicksToWait: The maximum amount of time (specified in ‘ticks’) to wait for one/all (de-
pending on the xWaitForAllBits value) of the bits specified by uxBitsToWaitFor to become set.
EventBits_t xEventGroupClearBits(EventGroupHandle_t xEventGroup, const EventBits_t uxBitsTo-
Clear)
Espressif Systems 933
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