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PSoC™ 5, 3 & 1 Forum Discussions

IoVo_297831
Level 4
Level 4
First like received

Hi,

   

Can we in PSoC5LP wake up the CPU every 1ms with accurate timing?
I saw that SleepTimer uses ILO and can wake up the CPU every 2ms (minimum and not with accuracy).
Also, I did not manage to use GlobalSignal component.

   

The task is to wake up at t=0, process data (that takes about 100us) and then get back to sleep until t=1ms. This is repeated continuously.
Any ideas?

   

Thank you in advance.

   

Regards,
Yiannis

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1 Solution
ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

You can use a xtal osc but that impacts power significanly in sleep modes.

   

 

   

Alternatively you can feed a precision clock to a pin, sweep Vdd, and during production

   

test use a routine in PSOC to measure ILO, and create a correction table of F vs V..

   

That does not take into account temperature, that also could be raised under external

   

control, then flag PSOC to take another measurement to add to table. Then in normal

   

application do measurements and correct using table.

   

 

   

Actually easier than it sounds.

   

 

   

 

   

 

   

Regards, Dana.

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ETRO_SSN583
Level 9
Level 9
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How accurate does the timing have to be ? The ILO ranges from .5 to 2 Khz when used

   

in low power.

   

 

   

 

   

 

   

Regards, Dana.

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IoVo_297831
Level 4
Level 4
First like received

Thank you very much for your answer.

   

The accuracy should be better than 5% (may be 1%, I am not able to give a safe answer right now).
But I did not manage to use ILO to produce timing shorter than 2msec (0.5KHz).

   

If ILO can be trimmed at 2KHz (I did not try that) then may be it is enough (in conjunction with the use of SleepTimer component).
But I am searching for a better solution.

   

Regards,
Yiannis

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ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

You can use a xtal osc but that impacts power significanly in sleep modes.

   

 

   

Alternatively you can feed a precision clock to a pin, sweep Vdd, and during production

   

test use a routine in PSOC to measure ILO, and create a correction table of F vs V..

   

That does not take into account temperature, that also could be raised under external

   

control, then flag PSOC to take another measurement to add to table. Then in normal

   

application do measurements and correct using table.

   

 

   

Actually easier than it sounds.

   

 

   

 

   

 

   

Regards, Dana.

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IoVo_297831
Level 4
Level 4
First like received

Thank you very much for your help.

   

The target is to get into sleep mode and not only to alternate active mode.
So the main oscillators will be disabled.

   

I find it rather complex to measure and trim ILO but you gave me another idea.
By feeding a precision clock 1KHz to a pin PSoC could wake up from sleep at wanted time intervals.
The drawback is that we need to create somehow this accurate clock by another chip/component but may be it is worth to try.

   

Thank you once more for your reply.

   

Regards,
Yiannis

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ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

If you have access to the AC line that is a fairly accurate timing source.

   

 

   

http://electronics.stackexchange.com/questions/57878/how-precise-is-the-frequency-of-the-ac-electric...

   

 

   

Or use external osc, there are some that are very low power.

   

 

   

Regards, Dana.

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IoVo_297831
Level 4
Level 4
First like received

AC line is not available otherwise there was no special need for low power operation.
Thank you very much for your time.

   

Regards,
Yiannis

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ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

Glad to assist.

   

 

   

Regards, Dana.

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