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Do I need a Pull up resistor for every item on the i2c bus?

 
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Nick
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Do I need a Pull up resistor for every item on the i2c bus?
PostPosted: Wed Oct 20, 2004 11:42 am     Reply with quote

I have two ICs the RTC(DS1307) and a EEPROM (24LC32) on a I2C bus, do I need a pull up resistor on each of the lines I2c for both devices? I 'think' i wouldnt since its basically using the same line just has two resistors on it, but I'm not sure how I would look up that type of information.

Thanks,

Nick
Kasper



Joined: 14 Jan 2004
Posts: 88
Location: Aurora, Ontario, Canada

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PostPosted: Wed Oct 20, 2004 11:54 am     Reply with quote

no.. just one set for each bus.
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Wed Oct 20, 2004 11:54 am     Reply with quote

You need only 1 resistor on each line (clock and data)
Nick
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PostPosted: Wed Oct 20, 2004 12:01 pm     Reply with quote

Thanks guys!
valemike
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In a noisy environment, you'll probably even need capacitors
PostPosted: Wed Oct 20, 2004 1:55 pm     Reply with quote

If your board is noisy, beware, you may get noise.

In the past, i encountered i2c bus circuits where there are capacitors and series resistors to filter out noise. This also limits your i2c bus speeds but will block out high frequency noise.
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