If a port defines MICROPY_SOFT_TIMER_TICKS_MS then soft_timer assumes a
SysTick back end, and provides a soft_timer_next variable that sets when
the next call to soft_timer_handler() should occur.
Otherwise, a port should provide soft_timer_get_ms() and
soft_timer_schedule_at_ms() with appropriate semantics (see comments).
Existing users of soft_timer should continue to work as they did.
Signed-off-by: Damien George <damien@micropython.org>
The previous computation incorrectly assumed that the uint32_t ticks
counter MICROPY_SOFT_TIMER_TICKS_MS was in the range [0,0x80000000) where
its actually [0,0xffffffff]. This means the diff calculation can be
simplified compared to the original implementation copied from
utime_mphal.c, which has to deal with a ticks range constrained by the
small int range.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
Before, both uwTick and mp_hal_ticks_ms() were used as clock source. That
assumes, that these two are synchronous and start with the same value,
which may be not the case for all ports. If the lag between uwTick and
mp_hal_ticks_ms() is larger than the timer interval, the timer would either
rush up until the times are synchronous, or not start until uwTick wraps
over.
As suggested by @dpgeorge, MICROPY_SOFT_TIMER_TICKS_MS is now used in
softtimer.c, which has to be defined in a port's mpconfigport.h with
the variable that holds the SysTick counter.
Note that it's not possible to switch everything in softtimer.c to use
mp_hal_ticks_ms() because the logic in SysTick_Handler that schedules
soft_timer_handler() uses (eg on mimxrt) the uwTick variable directly
(named systick_ms there), and mp_hal_ticks_ms() uses a different source
timer. Thus it is made fully configurable.
Damien George
Jim Mussared
robert-hh