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DS1307 problem

 
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kukac24



Joined: 15 Oct 2007
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DS1307 problem
PostPosted: Tue Feb 23, 2010 9:17 am     Reply with quote
I designed a PCB with PIC18F2520 and DS1307 communicating through I2C.
I have some problem with that communication. The pull up resistors are installed for each I2C line.

The distance of the pull up resistors is how considerable from the master or from slave?

Thanx in advance :)
Ttelmah
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PostPosted: Tue Feb 23, 2010 9:36 am     Reply with quote
What matters is the bus capacitance, and the frequency you are running it.
What value have you used for the resistors?. How long is the bus?. What gap have you used the adjacent tracks (power plane?)?. What frequency are you running the bus?.

Best Wishes
kukac24



Joined: 15 Oct 2007
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PostPosted: Sun Feb 28, 2010 2:45 am     Reply with quote
I tried the pull ups with 4k7 and 10k. The freq. was tried with FAST and SLOW as well.
The result is the same, when I send the time to LCD, there is only 45:85:85.
The quartz is 32kHz, without battery
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Sun Feb 28, 2010 3:04 am     Reply with quote
See these threads on the "45:85:85" problem with the DS1307:
http://www.ccsinfo.com/forum/viewtopic.php?t=19926
http://www.ccsinfo.com/forum/viewtopic.php?p=29784
http://www.ccsinfo.com/forum/viewtopic.php?p=94498
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