WDT with RTC caution!!!

[Anonymous]

Thanks to Bob,

   

I almost did implement RTC with WDT. and Now I want to know some caution about this process

       

1. I implemented 2 years-period timer with RTC. I used WDT2 with my generated interrupt.

   

but I worried about distortion. because of RTC, WDT2 must operate correctly. so tell me about caution that can distort WDT2.

       

2. can you tell me about guaranteed error related to RTC? last question, you said RTC could be almost precise. but i doubt that because of

   

clock accuracy, crystal characteristic or  load capacitance.

       

3. and now I calculate current in circumstance that is between deep sleep and active. but in datasheet. only wake time(25us) existed.

   

but in order to calculate exact time. I must know about code execution time, deep sleep time, active time during 1s.

       

- sean

[Bob_Marlowe]

Maintaining the precision of the 32kHz clock is on you allone.

   

Precision depends on

   

    
• Initial crystal precision
    
• Temperature
    
• Aging of the components
   

   

All these factors are not related to the PSoC

   

High precision clock crystals can be trimmed to 20ppm precision. Within 2 years = 2*365*24*60*60s = 63072000s you will have to expect a deviation of 63072000s*0,00002 = 1261,44s = 21minutes.

   

When you cannot live with that you will need to correct the clock by connecting to a radio-controlled clock module. Additionally you could consider using energy harvesting (Solar, piezo)).

   

in order to calculate exact time. I must know about code execution time, deep sleep time, active time during 1s.

   

I would suggest you to measure your program execution times yourself.

       

Bob

[Anonymous]

Thanks. I misunderstood sleep process will divided into some sections.

   

and fortunately clock is only affected by ppm.

   

Thanks for your help

       

- sean