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sukumar
stranger

Reged: Jul 12 2007
Posts: 4
Loc: Tamilnadu, INDIA

DS1307 interfacing with PIC16f877 or 877a
#28414 - Thu Jul 12 2007 07:41 AM Attachment (782 downloads)

I already replied for a forum question, but i found it is useful if i post my code here, Enjoy with the code

--------------------
Sukumar.M

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Arjun
stranger

Reged: Mar 21 2009
Posts: 7

Re: DS1307 interfacing with PIC16f877 or 877a [Re: sukumar]
#103512 - Wed Mar 25 2009 05:58 PM

i tried this code .. it doesnt work !!

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Dan Henry
Guru

Reged: Oct 16 2003
Posts: 3872
Loc: Colorado

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Arjun]
#103562 - Thu Mar 26 2009 12:42 AM

Quote:

i tried this code .. it doesnt work !!

You neglected to attach the fix you are sharing.

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Arjun
stranger

Reged: Mar 21 2009
Posts: 7

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Dan Henry]
#103842 - Fri Mar 27 2009 10:31 AM Attachment (199 downloads)

Thank you Dan for pointing that out. Iv attached the fix this time around.
i tried debugging it ..
everything works well untill ds1307_init();
once the hardware goes into this function and calls DS1307Write() .. this is when the problem starts ..
im using a PIC 16f877a with a 20 MHZ crystal ..

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Dan Henry
Guru

Reged: Oct 16 2003
Posts: 3872
Loc: Colorado

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Arjun]
#103872 - Fri Mar 27 2009 11:55 AM

Quote:

im using a PIC 16f877a with a 20 MHZ crystal ..

I think your I2C BRG is too fast. At 20MHz, shouldn't it be 63 for Fscl of 100KHz?

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Arjun
stranger

Reged: Mar 21 2009
Posts: 7

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Dan Henry]
#103882 - Fri Mar 27 2009 12:18 PM

i didnt get you .. 20 MHz is the crystal freq of 16f877 and the oscillator used with DS1307 is 32.769 KHz ..
i appreciate your guidance !!

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Dan Henry
Guru

Reged: Oct 16 2003
Posts: 3872
Loc: Colorado

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Arjun]
#103952 - Fri Mar 27 2009 02:51 PM

Quote:

i didnt get you .. 20 MHz is the crystal freq of 16f877 and the oscillator used with DS1307 is 32.769 KHz ..
i appreciate your guidance !!

What I was referring to has nothing to do with the RTC's oscillator, but rather about the I2C bus clocking frequency. That said, you can ignore my previous post. I had referred to table 9-3 in the data sheet, which is subject to MSSP errata that I had forgotten about. Your value of 49 is correct for 100KHz I2C bus clocking.

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Arjun
stranger

Reged: Mar 21 2009
Posts: 7

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Dan Henry]
#103962 - Fri Mar 27 2009 03:21 PM

:-)
ya .. but i still can't figure out why SSPIF doesnt get set ..

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Dan Henry
Guru

Reged: Oct 16 2003
Posts: 3872
Loc: Colorado

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Arjun]
#103972 - Fri Mar 27 2009 03:23 PM

Do you have pull-ups on SDA and SCL?

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Arjun
stranger

Reged: Mar 21 2009
Posts: 7

Re: DS1307 interfacing with PIC16f877 or 877a [Re: Dan Henry]
#104002 - Sat Mar 28 2009 09:57 AM

yes .. 10k each

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