xEventGroupSetBits()

event_groups.h

1EventBits_t xEventGroupSetBits( EventGroupHandle_t xEventGroup,
2                                const EventBits_t uxBitsToSet );

Set bits (flags) within an RTOS event group. This function cannot be called from an interrupt. xEventGroupSetBitsFromISR() is a version that can be called from an interrupt.

Setting bits in an event group will automatically unblock tasks that are blocked waiting for the bits.

The RTOS source file FreeRTOS/source/event_groups.c must be included in the build for the

xEventGroupSetBits()

function to be available.

Parameters:

xEventGroup

The event group in which the bits are to be set. The event group must have previously been created using a call to xEventGroupCreate().
uxBitsToSet

A bitwise value that indicates the bit or bits to set in the event group. For example, set
```
uxBitsToSet
```
to 0x08 to set only bit 3. Set
```
uxBitsToSet
```
to 0x09 to set bit 3 and bit 0.

Returns:

The value of the event group at the time the call to
```
xEventGroupSetBits()
```
returns.

There are two reasons why the returned value might have the bits specified by the
```
uxBitsToSet
```
parameter cleared:
1. If setting a bit results in a task that was waiting for the bit leaving the blocked state then it is possible the bit will have been cleared automatically (see the
```
xClearBitOnExit
```
  parameter of xEventGroupWaitBits()).
2. Any unblocked (or otherwise Ready state) task that has a priority above that of the task that called
```
xEventGroupSetBits()
```
  will execute and may change the event group value before the call to
```
xEventGroupSetBits()
```
  returns.

Example usage:

1#define BIT_0	( 1 << 0 )
2#define BIT_4	( 1 << 4 )
3
4void aFunction( EventGroupHandle_t xEventGroup )
5{
6    EventBits_t uxBits;
7
8    /* Set bit 0 and bit 4 in xEventGroup. */
9    uxBits = xEventGroupSetBits(
10                                 xEventGroup,    /* The event group being updated. */
11                                 BIT_0 | BIT_4 );/* The bits being set. */
12
13    if( ( uxBits & ( BIT_0 | BIT_4 ) ) == ( BIT_0 | BIT_4 ) )
14    {
15        /* Both bit 0 and bit 4 remained set when the function returned. */
16    }
17    else if( ( uxBits & BIT_0 ) != 0 )
18    {
19        /* Bit 0 remained set when the function returned, but bit 4 was
20           cleared. It might be that bit 4 was cleared automatically as a
21           task that was waiting for bit 4 was removed from the Blocked
22           state. */
23    }
24    else if( ( uxBits & BIT_4 ) != 0 )
25    {
26        /* Bit 4 remained set when the function returned, but bit 0 was
27           cleared. It might be that bit 0 was cleared automatically as a
28           task that was waiting for bit 0 was removed from the Blocked
29           state. */
30    }
31    else
32    {
33        /* Neither bit 0 nor bit 4 remained set. It might be that a task
34           was waiting for both of the bits to be set, and the bits were cleared
35           as the task left the Blocked state. */
36    }
37}

xEventGroupSetBits()

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