Hello Mattia,
On 24/12/2020 11:24, Mattia Bottaro wrote:
I need to develop a multitasking real-time application with RTEMS
(preferably in Ada, but also C solutions are welcomed). I see that I
can use the Classic API
<https://docs.rtems.org/branches/master/c-user/index.html>, but they
are unsuitable to my purposes. As you can read here
<https://docs.rtems.org/branches/master/c-user/task/directives.html#task-wake-when-wake-up-when-specified>,
the rtems_task_wake_when directive is too coarse: "The timing
granularity of this directive is a second.".
I need to work with microseconds-granularity and I cannot find how to
do it.
this limitation is do some implementation constraints which no longer
apply. From an API point of view
/**
* @ingroup RTEMSAPIClassicTypes
*
* @brief This type represents Classic API calendar times.
*/
typedef struct {
[...]
/**
* @brief This member contains the clock tick of the second with
values from 0
* to rtems_clock_get_ticks_per_second() minus one.
*/
uint32_t ticks;
} rtems_time_of_day;
it would be possible to also specify the clock driver ticks of a time
point. The rtems_task_wake_when() uses _Thread_Timer_insert_realtime()
which uses a time with a nanoseconds resolution. It would be easy to
change the implementation of rtems_task_wake_when() to use the clock
driver ticks.
As already mentioned, the clock_nanosleep() provides this functionality
already.
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