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Forum Index : Microcontroller and PC projects : CMM2 1 second tick question

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Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 952
Posted: 12:47pm 17 Nov 2021
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If nothing goes right ... turn left
 
Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 952
Posted: 12:55pm 17 Nov 2021
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Dear forum members.

For research on a real time clock accuracy, I would need a 1Hz adjustable frequency.
Easy to do with a "settick" command... But then my adjustment range for the timing is quite coarse. 999ms, 1000ms, 1001ms

Is there any way (on the CMM2, because I have a lot of data to process) to create a 1Hz square wave that can be adjusted finer (i.e. in 10us or even 1us steps).
In essence I want to create a PLL that locks to an external 1Hz signal, and the PLL is controlled from ASCII (numerical) output of the system I want to inspect.

Any help is welcome,

Volhout

P.S. if you want the details: the system to inspect makes an error during the wrap around of a 32.768kHz (HW counter) and the increment of the second counter (software) when an interrupt comes in between. In my current test setup once per 8 hours this happens. I am trying to force the external interrupts to exactly happen at the wrap around, in stead of wait until it occurs.
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Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 1196
Posted: 02:58pm 17 Nov 2021
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10kHz PWM fed back into a counter then set a flag every time it reaches 10,000?

Normally you'd be aiming for an accurate 1Hz to measure something against. :)
-- Mick

Zilog Inside! nascom.info for Nascom & Gemini
 
Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 952
Posted: 10:14pm 17 Nov 2021
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I was hoping to use one of the 2 32 timers to create a high resolution pwm, that would be fixed at 50%, but the frequency could be set to 1Hz. With high resolution.
Since i am debugging a sw timer, this one must be full HW, hence the stm32 32 bit timer.
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matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 5460
Posted: 10:38pm 17 Nov 2021
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  Quote  I was hoping to use one of the 2 32 timers to create a high resolution pwm


You could do it with timer2, the output would be on PA15 (pin 18 on the connector). To set it up you are going to need to read the relevant sections of the reference manual and poke some registers accordingly (all do-able from basic). Doing this would break the fast count function but nothing else.
 
Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 952
Posted: 08:12am 18 Nov 2021
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Thanks... that was what I was looking for.

Volhout
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