/** Wait until specified time:
@param when time to sleep until
@return current time. */
pit_tick_t pit_wait_until (pit_tick_t when)
{
when <<= 8;
while (1)
{
pit_tick_t diff;
pit_tick_t now;
now = pit_get () << 8;
diff = now - when;
if (diff < (PIT_OVERRUN_TICKS_MAX << 8))
return now;
}
}
/** Wait for specified period:
@param period how long to wait
@return current time. */
pit_tick_t pit_wait (pit_tick_t period)
{
return pit_wait_until (pit_get () + period);
}
/*! @brief Kernel start.
* Start the kernel running within an infinite loop.
* @return None.
*/
void
kernel_start (void)
{
uint32_t i;
uint32_t tick = 0;
uint32_t now = 0;
uint32_t then = 0;
uint32_t diff = 0;
uint32_t extra = 0;
then = pit_get ();
while (1)
{
/* If there has been another tick then decrement
* the current block period of each task, unless it's already
* blocked for 0 time
*/
now = pit_get ();
if (then > now)
diff = (MAX_INT - then) + now; // Deal with wrap-around
else
diff = now - then;
tick = tick + (diff / ACCURACY_DIVIDER);
extra = diff % ACCURACY_DIVIDER;
then = now - extra;
if (tick > 0)
{
//USB_INFO ("tick = %d", tick);
for (i = 0; i < tasks_registered; i++)
{
if (tasks[i].blocked_for > 0)
tasks[i].blocked_for -= tick;
}
tick = 0;
/* Run through the list of tasks round-robin style
* If a task is in a blocked state then it is not run
*/
for (i = 0; i < tasks_registered; i++)
{
if (tasks[i].state == TASK_READY)
{
/* If the tasked is blocked for 0 time then it can be run */
if (tasks[i].blocked_for <= 0)
{
/* Run the task */
tasks[i].func (tasks[i].data);
/* Block the task again for the period it specifies */
tasks[i].blocked_for = tasks[i].period;
}
}
}
}
}
}
