FreeRTOS Support Archive
The FreeRTOS support forum is used to obtain active support directly from Real
Time Engineers Ltd. In return for using our top quality software and services for
free, we request you play fair and do your bit to help others too! Sign up
to receive notifications of new support topics then help where you can.
This is a read only archive of threads posted to the FreeRTOS support forum.
The archive is updated every week, so will not always contain the very latest posts.
Use these archive pages to search previous posts. Use the Live FreeRTOS Forum
link to reply to a post, or start a new support thread.
[FreeRTOS Home] [Live FreeRTOS Forum] [FAQ] [Archive Top] [March 2015 Threads]
Hi,
Is it possible to use ulTaskNotifyTake() with a zero wait time from an ISR? I want to use it as a binary semaphore to get hold of a storage buffer.
Regards,
Remco Poelstra
It might [unofficially] be possible, but looking at the code I would say it would depend on which port you are using....which are you using?
Regards.
Hi Remco,
I don't know if it is safe to call ulTaskNotifyTake() from an interrupt, but: normally the xxxTake would be called from within a task, and xxxGive from within an interrupt or a task.
Now you get an interrupt and you want to see if "a resource" is available?
Isn't a simple volatile flag enough for this?
~~~~~
#define FLAGBUSY 1
volatile uint32t flags;
void isr( void )
{
/* Here 'flags' is only read, not written. */
if( ( flags & FLAG_BUSY ) == 0 )
{
/* Buffer is available */
}
}
void update_buffer ()
{
flags |= FLAG_BUSY;
/* Buffer may be accessed */
flags &= ~( FLAG_BUSY );
}
~~~~~
Regards.
Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.