I2C With 3,3 Volt

[savnik]

Always i use on my projects with I2C , 1OK resistor without problem.
Now i am afraid for the NS73M , because work at 3,3 volt.
I have make the PCB and tomorrow maybe i will test.
Maybe i Set pull-up to 3.3v to test , or i run all at 3,3 volt (and LCD).
Have any problem with 16f628a with 3,3 volt;

[SmugWimp]

You might not be able to get the LCD to work on 3.3v, but you can always put a regulator or resistors in to drop voltage for the NS73M...

I am having my own problems with this situation.

I hope you are successful, and I hope you share

Cheers!

SmugWimp

[nomad]

curious, but doesn't PBP run the clock and data as open collector? (playing with tris).
the 628a doesn't have i2c hardware so would have to be done by PBP.
as I've seen the define to make the clock bipolar I've wondered about that.
and reading the lib seen :

i2chigh
      ifndef I2C_INTERNAL
        bsf     FSR, 7          ; 1 Point to TRIS
      endif
        iorwf   INDF, F         ; 1 Set high (input)

or similar all about the i2c routines.

if so, then pullups to 3.3v appears to be all that's needed.?
(assuming the pic recognises 3.3v as a high)

maye that's why Acetronics said

But just verify you use TTL inputs of the PIC and not Schmitt trigger ones ...

Something I'm missing?

[BigWumpus]

You need a bidirektional Level-shifter !

Look here:
http://www.standardics.philips.com/s...df/an97055.pdf
http://www.semiconductors.philips.co...#levelshifting

You need only 2 little MOSFETs!

[savnik]

Yesterday i test it and all is ok.
I use 5volt for 16f628a + LCD and 3,3 volt for NS73M
My problem with NS73M is that have spurius near the local frequency.
Thanks all for help.