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Re: Cortex-M1/3 SysTick/RTC
- From: Andrew Lunn <andrew at lunn dot ch>
- To: "simon dot kallweit at intefo dot ch" <simon dot kallweit at intefo dot ch>
- Cc: ecos-discuss at ecos dot sourceware dot org
- Date: Thu, 11 Sep 2008 17:35:42 +0200
- Subject: Re: [ECOS] Cortex-M1/3 SysTick/RTC
- References: <48C936B3.2020505@intefo.ch>
On Thu, Sep 11, 2008 at 05:18:11PM +0200, simon.kallweit@intefo.ch wrote:
> I had a quick look at the ecos clock system. The clock is usually
> implemented using a timer interrupt in the variant or platform code.
> With the Cortex-M1/3, we have a SysTick timer which belongs to the
> architecture itself. I think we should use the SysTick as the clock
> source.
I agree. Use the NVIC clock. It is there, always. It makes a port to a
new target so much simpler since often the clock is often a hard part.
The STM32 additionally provides an RTC, but I guess this should
> be implemented as a Wallclock driver, right? A quick look over the
> wallclock interface showed that there is no function for setting wakeup
> alarms. Is this functionality defined elsewhere or is it missing?
I just had a very quick look at the date sheet. The RTC looks like it
could be used for a wallclock, however it depends on the hardware. Is
it equipped with a 32.786 Hz clock? Is it using the internal RC clock?
is it calibrated etc? So writing a generic STM32 wallclock driver
might not be possible, it probably needs to the target specific.
The wallclock interface does not support alarms, etc.
> Concerning the system clock interrupt. Why is it called
> CYGNUM_HAL_INTERRUPT_RTC? This can be a bit misleading, but I guess has
> historic reasons.
No idea. It was before my time.
Andrew
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