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  1. #1
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    Default Using Pic as a digital clock/timer. How accurate?

    Hello,
    I am trying to use the pic as a clock timer that displays the time hour and minutes but also i would like it to have a featured timer that the user can set. The timer will activate a motor.
    will the time be accurate enough?
    I am using the pic basic pro and the usb programmer.
    What's the easiest way to get this done? any suggestions is appreciated.
    Thanks

  2. #2
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    Default

    Bottom line - It will only be as accurate as the oscillator used. The PIC is not the limiting factor.

    SteveB

  3. #3
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    Default

    Quote Originally Posted by rocky79 View Post
    Hello,
    I am trying to use the pic as a clock timer that displays the time hour and minutes but also i would like it to have a featured timer that the user can set. The timer will activate a motor.
    will the time be accurate enough?
    I am using the pic basic pro and the usb programmer.
    What's the easiest way to get this done? any suggestions is appreciated.
    Thanks
    I give u example of simple timer and clock where user can set when they want to high certain port of the PIC. THere is only two buttons need to be used. First button to toggle from one menu to other menu. For example if we press this button then we can change from setting minute to the hour setting menu. Other button function is to set(increase) the value of second, minute, hour and etc. But how accurate this timer is depend on the oscillator u use as Steve B had said before. Attached herewith is the code: Please advise if you have some input on this code. Thanks.

    symbol second=2000
    symbol second2=1000

    second1 VAR BYTE
    minute VAR BYTE
    hour VAR BYTE
    day VAR BYTE
    time1 VAR BYTE
    time2 VAR BYTE

    second1=0
    minute=0
    hour=0
    day=0
    time1=0
    time2=0
    masa3=0


    hourset:
    Pause 200
    LCDOut $FE,1
    LCDOut "Set Hour"
    LCDOut $FE,$C0
    LCDOut "TIME:",DEC2 day,".",DEC2 hour,".",DEC2 minute,".",DEC2 second

    IF PORTB.5=1 Then GoSub addhour
    IF hour>23 Then hour=0
    IF PORTB.6=1 Then GoSub time1set
    GoTo hourset

    hour1set:
    Pause second2
    LCDOut $FE,1
    LCDOut "Set Time MotorOn1"
    LCDOut $FE,$C0
    LCDOut "Minute:",DEC2 time1

    IF PORTB.5=1 Then GoSub addtime1
    IF time1>59 Then time1=0
    IF PORTB.6=1 Then GoSub time2set
    GoTo time1set

    time2set:
    Pause second2
    LCDOut $FE,1
    LCDOut "Set Time MotorOn2"
    LCDOut $FE,$C0
    LCDOut "Day:",DEC2 time2

    IF PORTB.5=1 Then GoSub addtime2
    IF time4>99 Then time2=0
    IF PORTB.6=1 Then GoSub changeday
    GoTo time2set
    End

    addhour:
    IF PORTB.5=1 Then GoSub timer
    Return

    timer:
    second1=0
    minute=minute+1
    IF minute > 59 Then
    minute=0
    hour=hour+1
    IF hour >23 Then
    hour=0
    day=day+1
    IF day>30 Then
    dayi=0
    EndIF
    EndIF
    EndIF
    Pause 500
    Return

    addtime1
    IF PORTB.5=1 Then time1=time1+1
    Pause 500
    Return

    addtime2
    IF PORTB.5=1 Then time2=time2+1
    Pause 500
    Return

    changeday:
    IF PORTB.6=1 Then GoTo day


    day:
    Pause second
    saat=saat+1
    IF second1 >59 Then GoSub timer


    LCDOut $FE,2
    LCDOut "ON:",DEC2 time1,">",DEC2 time2,">"
    LCDOut $FE,$C0
    LCDOut "TIME:",DEC2 day,".",DEC2 hour,".",DEC2 minute,".",DEC2 second1


    IF (minute=time1 OR minute=time2) Then High PORTB.7
    IF (minute=time1+1 OR minute=time2+1) Then Low PORTB.7
    Goto day

  4. #4
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    Thumbs up

    Thanks Fazan for the code but one thing i didn't understand is how do i get the actual seconds by simply counting? if you count from 1 to 60 does it mean its 1 to 60seconds? can you clarify how you convert from the simple execution time for the count to actual seconds.
    Thanks a lot

  5. #5
    Join Date
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    Salt Lake City, Utah USA
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    Smile

    Another Option - might help get you started
    http://www.picbasic.co.uk/forum/showthread.php?t=2129
    Paul Borgmeier
    Salt Lake City, UT
    USA
    __________________

  6. #6
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    Default

    Quote Originally Posted by rocky79 View Post
    Thanks Fazan for the code but one thing i didn't understand is how do i get the actual seconds by simply counting? if you count from 1 to 60 does it mean its 1 to 60seconds? can you clarify how you convert from the simple execution time for the count to actual seconds.
    Thanks a lot
    How accurate it is depend on the speed of oscillator that u use.

  7. #7
    Join Date
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    Default

    Also, the ambient temp is the most effective factor.

    You can get a slow running or fast running clock ticks depending on the temperature of the environment in which your PIC is running. (ambient temp)

    --------------------------

  8. #8
    Join Date
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    Location
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    3,541

    Wink Have a happy new year, Rocky !!!

    Hi, Rocky

    I just built Thermo-baro-clock with a MS5534 sensor.( 16F876 ) the clock is driven by a 32.7... khz "clock crystal" connected to RC0,RC1 pins and using TMR1 ovf interrupt.

    The only way to adjust reading is to trim the TMR1 preset ( 32768 ...in theory ). an adjustable capacitor parallelled to one of the xtal load caps could also help a bit.

    Possible also to use two pushbuttons to inc/dec the TMR preset value, you then store in the EEPROM ... but do not forget to limit the trim range !!!

    But as always ... no simple automatic trimming.

    Absolute references will always be our main headaches ... cause there's none naturally existing !!!

    best regards
    Alain
    Last edited by Acetronics2; - 22nd January 2007 at 12:41.
    ************************************************** ***********************
    Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
    ************************************************** ***********************
    IF there is the word "Problem" in your question ...
    certainly the answer is " RTFM " or " RTFDataSheet " !!!
    *****************************************

  9. #9
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    Wink Happy New Year Acetronics

    Thanks guys for all the help and links. I found a chip that does all the hard work for me on top of that it is featured with 2 alarm settings.
    http://pdfserv.maxim-ic.com/en/ds/DS3232.pdf

    I will give it try and will see how it goes.
    Thanks again

  10. #10
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    Default

    I've used the clock only version of the chip (a temp. compensated oscilattor) and can attest to it's accuracy. It was hard to get a hold of at the time, though supply might be better now.

    SteveB

  11. #11
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    Default

    Quote Originally Posted by SteveB View Post
    I've used the clock only version of the chip (a temp. compensated oscilattor) and can attest to it's accuracy. It was hard to get a hold of at the time, though supply might be better now.

    SteveB
    Hello Steve,
    I am using the RTC DS3232 from dallas. you said you have used it before. Can you share your picbasic code? I am having trouble setting the time.
    when i read the time and date. I get them all as 4.
    Here is mine:
    'Using the pic 16f630

    include "modedefs.bas"
    define OSCCAL_1k 1
    CMCON=%0000011' Turn off comparator module


    minutes var byte
    hours var byte
    day var byte
    date var byte
    month var byte
    year var byte

    reset Var PORTC.0

    rtcyear var byte
    rtcday var byte
    rtcmonth var byte
    rtcdate var byte
    rtchour var byte
    rtcmin var byte
    rtcsec var byte

    ' Set initial time to 8:00:00AM 07/16/99
    rtcyear = $99
    rtcday = $06
    rtcmonth = $07
    rtcdate = $16
    rtchour = $08
    rtcmin =0
    rtcsec =0

    startbigNums con 2
    endBigNums con 3
    clrLCD CON 12
    backLightOn con 14
    backLightOff con 15
    cursorPos con 16
    enter con 10
    bell con 7
    b2 var byte
    CONTL CON %01101000


    Low reset 'reset the RTC
    input reset ' undo reset..basically it puts pin reset at high impedance

    'Set the time
    I2cwrite PORTC.2,PORTC.1,CONTL,$01,[rtcmin] 'minutes
    I2cwrite PORTC.2,PORTC.1,CONTL,$02,[rtchour]'hours
    I2cwrite PORTC.2,PORTC.1,CONTL,$03,[rtcday] 'day
    I2cwrite PORTC.2,PORTC.1,CONTL,$04,[rtcdate]'date
    I2cwrite PORTC.2,PORTC.1,CONTL,$05,[rtcmonth]'month
    I2cwrite PORTC.2,PORTC.1,CONTL,$06,[rtcyear] 'year


    pause 10
    'Low reset
    'input reset
    I2cread PORTC.2,PORTC.1,CONTL,$01,[minutes]
    I2cread PORTC.2,PORTC.1,CONTL,$02,[hours]
    I2cread PORTC.2,PORTC.1,CONTL,$03,[day]
    I2cread PORTC.2,PORTC.1,CONTL,$04,[date]
    I2cread PORTC.2,PORTC.1,CONTL,$05,[month]
    I2cread PORTC.2,PORTC.1,CONTL,$06,[year]

    serout2 0,16780,[clrLCD,"Time",hex hours,":",hex minutes,enter,_
    "date:",hex date,"/",hex month,"/",hex year]
    end

  12. #12
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    Default

    Bad wording on my part. What I ment was that I have used one of the temperature compensated oscillators (the DS32kHz, not the DS3232 RTC) with other RTCs and as an input to the PIC timers, and they worked well. I'll have a glance at you code and the Datasheet to see if I can spot anything.

    With other DSXXXX RTCs, I have seen the need to set some of the registers to appropriate setting before things work correctly. So that is one place to start.

    I'll get back if I see anything.

    SteveB

  13. #13
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    Location
    Mentor, Ohio
    Posts
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    Smile

    Hi Rocky,

    I think your code is missing the clock register constants. I use the DS1337 RTC from Maxim. The code for this chip was posted here either in 2004 or 2005 by Tonigalea. This chip also has two alarms. The key to an accurate clock is as was mentioned before. But you must also use the correct crystal. The DS1337, for example, must have a crystal with a 12.5pf capacitance load. When you look in a parts catalog, DigiKey for example, look for the capacitance load for 32,768 crystals. They are around $.50 or less.

    We also just covered RTC's with jcleaver using a DS1307. It looked like he also didn't list the RTC register constants. I sent him a copy of a program for that RTC and he got that going.

    I would give a serious look at Paul Borgmeier's Easy Accurate Clock programs as they are very easy to work with and setting up user interface for alarms should be very easy also.

    You asked a questions about the timing that no one seemed to answer. The PIC generates an internal time base which is derived from the Oscillator of the PIC divided by 4 so if you are using a 4mHz crystal then you PIC clock runs at 1mHz. Then there are programmable timers in the PIC that can be set up to count pulses then interrupt the PIC program to advance the clock program and/or do tasks at a specified time.

    Hope this helps.

    BobK

  14. #14
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    Default

    Bob,
    Can you specify what register constant i am missing? i look it up and i didn't see anything else i need to specify.Remember its the DS3232 i aim using so it might be slightly different than the other rtc's
    Please let me know

    thanks

  15. #15
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    Default

    Quote Originally Posted by SteveB View Post
    Bad wording on my part. What I ment was that I have used one of the temperature compensated oscillators (the DS32kHz, not the DS3232 RTC) with other RTCs and as an input to the PIC timers, and they worked well. I'll have a glance at you code and the Datasheet to see if I can spot anything.

    With other DSXXXX RTCs, I have seen the need to set some of the registers to appropriate setting before things work correctly. So that is one place to start.

    I'll get back if I see anything.

    SteveB
    Thanks steve! let me know if you find anything unusual or wrong i n my code...Thanks again

  16. #16
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    Smile

    Hi Rocky,

    Look on page 11 of the datasheet. The addresses in Hex and the register name under the function column are what you need. I have attached a listing example from a DS1337 program for an example. The datasheet had the same type of setup as this chip. You can't write any data to the RTC if it doesn't know where to put it.

    Boy if I'm wrong here I really apologize but I think I'm right. Please let me know.

    BobK
    Attached Files Attached Files
    Last edited by BobK; - 12th February 2007 at 19:26. Reason: Correct some errors.

  17. #17
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    Quote Originally Posted by BobK View Post
    Hi Rocky,

    Look on page 11 of the datasheet. The addresses in Hex and the register name under the function column are what you need. I have attached a listing example from a DS1337 program for an example. The datasheet had the same type of setup as this chip. You can't write any data to the RTC if it doesn't know where to put it.

    Boy if I'm wrong here I really apologize but I think I'm right. Please let me know.

    BobK
    Bob,

    That's what i have on my code if you look back. Here is a sample take the minutes sample for example:
    'Set the time
    I2cwrite PORTC.2,PORTC.1,CONTL,$01,[rtcmin] 'minutes
    the CONTL is the address of the RTC the $01 is the minutes register and the rtcmin is the value to be put in the register.
    I hope you find my mistake.

    Thanks

  18. #18
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    Smile

    Hi Rocky,

    Click on SEARCH and enter DS1337. Look at the post :example code for DS1337, dated 28Oct2004. The program shows the register addresses. If you don't have the addresses setup then the clock can't be set and it will not work properly.

    All of the addresses on page 11 of the datasheet need to be setup as constants. Take the list of addresses on the example code I attached on my last reply. Put them into your program and try them. I do understand you also may possibly have other issues with your setup but these constants need to be a part of your program.

    BobK

  19. #19
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    Wink HorrAY! it works

    Thanks Bob and all of you who replied to this post. My mistake was simple like usual. The RTC slave address is 7 bits so I added an extra zero to the left to make it 8 but i was wrong the zero should be to the right!

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