I2C Question....Going slightly mad!

[Wilksey]

Hi Guys,

Been a while since I have done any I2C, and can't find my old schematic.

Looking at interfacing the DS1307 to a PIC18.

The question, does the pull ups have to be a certain value or can I use my standard 10k's? I seem to have the figure 4.7k in my head, does it matter what the pull up resistance is for I2C?

Cheers

Wilksey

 

[upand_at_them]

Either one should work fine. I usually use 10K, because I have so many of them.

 

[Wilksey]

Thought so, just wanted to make sure!!

Thanks for the confirmation upand_at_them!

Wilksey

 

[Nigel Goodwin]

Thought so, just wanted to make sure!!

It's really VERY non-critical, it can vary over a massive range - but for it's intended purpose (multiple IC's over a LARGE television PCB) the values need to be lower, in order for it to overcome the capacitance of the tracks.

For short tracks to a single chip, it doesn't matter much at all.

 

[Wilksey]

Thanks Nigel!

Yes it will be short tracks to a single chip.

Cheers!!