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On Fri, Sep 7, 2018 at 11:50 AM, Jerry Gaffke wrote:

Here's an old post regarding the use of a 5v i2c LCD display with the Raduino:
? ??/g/BITX20/message/39966

Summary:
The two wire i2c bus is also used to talk to the 3.3v si5351, so we can't operate the i2c bus at 5v.
Most i2c devices such as an i2c LCD display will include pullup resistors to 5v, they should be removed.
The 3.3v pullup resistors R13 and R14 on the Raduino are sufficient.

There should be only one set of pullups on the i2c bus.
If you try to put 10 i2c devices (such as LCD displays) on an i2c bus and they all have
their own pullups, it won't work.? The open-collector drivers will see too much current.

ArduinoLand has been running on 5v for the last 20 years, most of the world has since
moved on to 3.3v or less.? So hooking up a newer part like the si5351 to an Arduino Nano
is a bit more complicated than it should be.

Jerry

hey thanks too !

i have seen your post to late so i write now again..

when i was reading your post then i dont understand my I2C panel that's on my I2C Display in here. that is not the same i see at other pics by ubitx users they have showed.. and by the post pics above, you can see my I2C Display and there is nothing like an capacitor or resistor.. By the way i should ask "what ist an PULLUP Resistor?" i dont know this word, or is it the variable resistor that looks like a blue quadrat with a with plastic screw, to adjust the displays brightness, ..is that mean for pullup resistor? others not at my I2C panel and i dont know what you think about the KD8CEC website.. there would be a tutorial an there nothing was say about any 3.3v or desolder resistor.. that is making me crazy.. here ( l ) have you an idea for that website tutorial wasn't give information to the point of voltage on these pins using?

and what you say about my other idea, to desolder the I2C panel from Display and use it by put in the orignal display pins place? was that an option or there is an hiding problem too?

thanks