I used the Adafruit Si5351 board and an I2C display backpack? when I built the freq gen for my pre-raduino BITX40.? I'm doing the same thing for my ?BITX build.? Adafruit's board has a 3.3V regulator on board as well as level shift components so the I2C line can be fed 5.0 or 3.3V.? it's not as inexpensive as boards from the Far East, but the boat that delivers them is much faster!
?Andy, KG5RKP
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On Thu, Dec 21, 2017 at 12:03 pm, Jerry Gaffke wrote:
Blindly mixing 5v and 3.3v devices like your Nano and LCD and Si5351 may work.
Or may not.
Might even destroy something.
I'd definitely follow Rod's advice and remove the pullups on any 5v i2c LCD:
??/g/BITX20/message/36797
Otherwise you are dumping current from the 5v rail into the 3.3v Si5351 through those LCD pullup resistors.
Currents through those pullups may not be enough to be an issue,?
but the Si5351 is a critical part here and I would not want to piss it off.
One thing you don't want to do is to download a sketch that actively drives those i2c pins high to 5v,
then you would have some significant current going through the protection diodes at the Si5351's i2c pins.
Might even blow the Si5351
On Thu, Dec 21, 2017 at 11:43 am, Jack Purdum wrote:
Well, the Nano takes 5V so that has to be floating around somewhere and most LCD's are 5V devices. (Many TFT are 3.3V.)
?
