int sam_oneshot_start(struct sam_oneshot_s *oneshot, struct sam_freerun_s *freerun,
oneshot_handler_t handler, void *arg, const struct timespec *ts)
{
uint64_t usec;
uint64_t regval;
irqstate_t flags;
tmrinfo("handler=%p arg=%p, ts=(%lu, %lu)\n",
handler, arg, (unsigned long)ts->tv_sec, (unsigned long)ts->tv_nsec);
DEBUGASSERT(oneshot && handler && ts);
/* Was the oneshot already running? */
flags = enter_critical_section();
if (oneshot->running)
{
/* Yes.. then cancel it */
tmrinfo("Already running... cancelling\n");
(void)sam_oneshot_cancel(oneshot, freerun, NULL);
}
/* Save the new handler and its argument */
oneshot->handler = handler;
oneshot->arg = arg;
/* Express the delay in microseconds */
usec = (uint64_t)ts->tv_sec * USEC_PER_SEC + (uint64_t)(ts->tv_nsec / NSEC_PER_USEC);
/* Get the timer counter frequency and determine the number of counts need to achieve the requested delay.
*
* frequency = ticks / second
* ticks = seconds * frequency
* = (usecs * frequency) / USEC_PER_SEC;
*/
regval = (usec * (uint64_t)sam_tc_divfreq(oneshot->tch)) / USEC_PER_SEC;
tmrinfo("usec=%llu regval=%08llx\n", usec, regval);
DEBUGASSERT(regval <= UINT16_MAX);
/* Set up to receive the callback when the interrupt occurs */
(void)sam_tc_attach(oneshot->tch, sam_oneshot_handler, oneshot,
TC_INT_CPCS);
/* Set RC so that an event will be triggered when TC_CV register counts
* up to RC.
*/
sam_tc_setregister(oneshot->tch, TC_REGC, (uint32_t)regval);
/* Start the counter */
sam_tc_start(oneshot->tch);
/* The function sam_tc_start() starts the timer/counter by setting the
* bits TC_CCR_CLKEN and TC_CCR_SWTRG in the channel control register.
* The first one enables the timer/counter the latter performs an
* software trigger, which starts the clock and sets the counter
* register to zero. This reset is performed with the next valid edge
* of the selected clock. Thus it can take up USEC_PER_TICK microseconds
* until the counter register becomes zero.
*
* If the timer is canceled within this period the counter register holds
* the counter value for the last timer/counter run. To circumvent this
* the counter value of the freerun timer/counter is stored at each start
* of the oneshot timer/counter.
*
* The function up_timer_gettime() could also be used for this but it takes
* too long. If up_timer_gettime() is called within this function the problem
* vanishes at least if compiled with no optimisation.
*/
oneshot->start_count = sam_tc_getcounter(freerun->tch);
/* Enable interrupts. We should get the callback when the interrupt
* occurs.
*/
oneshot->running = true;
leave_critical_section(flags);
return OK;
}
int sam_oneshot_start(struct sam_oneshot_s *oneshot, oneshot_handler_t handler,
void *arg, const struct timespec *ts)
{
uint64_t usec;
uint64_t regval;
irqstate_t flags;
tcvdbg("handler=%p arg=%p, ts=(%lu, %lu)\n",
handler, arg, (unsigned long)ts->tv_sec, (unsigned long)ts->tv_nsec);
DEBUGASSERT(oneshot && handler && ts);
/* Was the oneshot already running? */
flags = irqsave();
if (oneshot->running)
{
/* Yes.. then cancel it */
tcvdbg("Already running... cancelling\n");
(void)sam_oneshot_cancel(oneshot, NULL);
}
/* Save the new handler and its argument */
oneshot->handler = handler;
oneshot->arg = arg;
/* Express the delay in microseconds */
usec = (uint64_t)ts->tv_sec * USEC_PER_SEC + (uint64_t)(ts->tv_nsec / NSEC_PER_USEC);
/* Get the timer counter frequency and determine the number of counts need to achieve the requested delay.
*
* frequency = ticks / second
* ticks = seconds * frequency
* = (usecs * frequency) / USEC_PER_SEC;
*/
regval = (usec * (uint64_t)sam_tc_divfreq(oneshot->tch)) / USEC_PER_SEC;
tcvdbg("usec=%llu regval=%08llx\n", usec, regval);
DEBUGASSERT(regval <= UINT16_MAX);
/* Set up to receive the callback when the interrupt occurs */
(void)sam_tc_attach(oneshot->tch, sam_oneshot_handler, oneshot,
TC_INT_CPCS);
/* Set RC so that an event will be triggered when TC_CV register counts
* up to RC.
*/
sam_tc_setregister(oneshot->tch, TC_REGC, (uint32_t)regval);
/* Start the counter */
sam_tc_start(oneshot->tch);
/* Enable interrupts. We should get the callback when the interrupt
* occurs.
*/
oneshot->running = true;
irqrestore(flags);
return OK;
}
