Okay, then I will just implement using rtems_clock_get_uptime_nanoseconds()
, similarly to how it was done in the lwIP sys_now implementation by Pavel.
Kind Regards
Robin
On Mon, 19 Apr 2021 at 19:53, Sebastian Huber <
sebastian.hu...@embedded-brains.de> wrote:
> On 19/04/2021 18:42, Gedare Bloom wrote:
>
> > On Mon, Apr 19, 2021 at 10:41 AM Gedare Bloom<ged...@rtems.org> wrote:
> >> On Mon, Apr 19, 2021 at 2:51 AM Robin Müller<robin.muelle...@gmail.com>
> wrote:
> >>> From 88ac5780f5597a8bb3bf68c6b37fe6694956faaf Mon Sep 17 00:00:00 2001
> >>> From: Robin Mueller<robin.muelle...@gmail.com>
> >>> Date: Mon, 19 Apr 2021 10:39:55 +0200
> >>> Subject: [PATCH] updated HAL_GetTick function
> >>>
> >>> Patch text went missing, here is the full version of the patch.
> >>> Provides implementation for HAL_GetTick but uses RTEMS.
> >>> Accounts for the tick base not being 1ms now
> >>> ---
> >>> bsps/arm/stm32h7/start/bspstart.c | 3 ++-
> >>> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/bsps/arm/stm32h7/start/bspstart.c
> b/bsps/arm/stm32h7/start/bspstart.c
> >>> index 2fc8133cca..e6e995a50c 100644
> >>> --- a/bsps/arm/stm32h7/start/bspstart.c
> >>> +++ b/bsps/arm/stm32h7/start/bspstart.c
> >>> @@ -32,9 +32,10 @@
> >>>
> >>> #include <stm32h7xx_hal.h>
> >>>
> >>> +/* Get number of milliseconds elapsed since startup */
> >>> uint32_t HAL_GetTick(void)
> >>> {
> >>> - return 0;
> >>> + return (rtems_clock_get_ticks_since_boot() * 1000) /
> rtems_clock_get_ticks_per_second();
> >> This is reasonable, but note that:
> >> 1. usually it is better to divide before multiplying, to reduce the
> >> chance of arithmetic overflows.
> >> 2. the ticks_since_boot is 32-bits, with 1000 Hz ticking it overflows
> >> in ~2 months
> >>
> >> I suggest you consider
> >> return rtems_clock_get_uptime_seconds()*1000;
> >>
> >> Or you can use rtems_clock_get_uptime_nanoseconds() / (10000000) if ms
> >> precision is needed.
> >>
> > I just saw that the HAL function also returns a u32, so it will
> > overflow anyway and it doesn't really matter what you do.
> >
> The HAL_GetTick() should still be correct, otherwise you have an
> infrequent bug which may or may not trouble you seriously. Maybe just do
> the computation with 64-bit floating point numbers or just
> rtems_clock_get_uptime_nanoseconds() / 1000.
>
> --
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> Herr Sebastian HUBER
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