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delay generation

mr.rohit

Delay generation using timer in pic18f46k22

 

I am using timer interrupt for delay generation in pic18f

when i generate  any delay using timer that time this delay is not proper which i want,it showing some difference in time.

i want knw what is the reason of that difference ?

plz help me...

thank u..

Parents

  • How precise and how accurate?

     

    Accurate timing comes down to a time base and synchronization.

     

    You can accomplish these tasks depending upon your requirements.

     

    Please share them if you want a good answer.

     

    DAB

  • in reply to DAB

    hello...

     

    I am working with Capacitive sensor using CTMU in pic18f46k22..I am refering AN1375 App note for CTMU..

    this microcontroller having CTMU unit for capacitive sensor.in CTMU registers , i am using 5.5uA internal current source,and 14us delay which is generated by timer interrupt for CTMU.

    calculations....

    c = 30 pf

    I = 5.5uA

    T = 14us

    v = ?

     

    according to mathematical calculation

    v = (I*T)/C

    v = (5.5uA * 14us)/30pf

    v = 2.56v

     

    my question is ,

    Can i use the time delay in millisecond using timer interrupt for CTMU ?

    plz help me, i am not able to understand the accurate calculations..

    thank u..

Reply
  • in reply to DAB

    hello...

     

    I am working with Capacitive sensor using CTMU in pic18f46k22..I am refering AN1375 App note for CTMU..

    this microcontroller having CTMU unit for capacitive sensor.in CTMU registers , i am using 5.5uA internal current source,and 14us delay which is generated by timer interrupt for CTMU.

    calculations....

    c = 30 pf

    I = 5.5uA

    T = 14us

    v = ?

     

    according to mathematical calculation

    v = (I*T)/C

    v = (5.5uA * 14us)/30pf

    v = 2.56v

     

    my question is ,

    Can i use the time delay in millisecond using timer interrupt for CTMU ?

    plz help me, i am not able to understand the accurate calculations..

    thank u..

Children
  • in reply to mr.rohit

    Hello,

    I am sorry, but I don't understand your question. What do you mean by

    Can i use the time delay in millisecond using timer interrupt for CTMU ?

     

    I personally haven't used CTMU unit in PICs, however, I've quickly gone through the referenced application note AN1375 and 18F46K22 datasheet. It is up to you, how you implement the delay (a timer, fixed length loop, ...).

     

    (BTW, I recommend reading application number 47. and 48. in that application note. Seems that engineers wanted to accompany the useful text with some fun image )