Re: [ECOS] Cortex-M1/3 SysTick/RTC

[Andrew Lunn <andrew at lunn dot 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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