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Re^2: i2c lcd Custom Characters

by anita2R (Scribe)
on Jun 10, 2016 at 19:52 UTC ( #1165359=note: print w/replies, xml ) Need Help??

in reply to Re: i2c lcd Custom Characters
in thread i2c lcd Custom Characters


I have seen a lot of comments about the i2c bus voltages and the Pi.

The GPIO pins in normal use are not 5 volt tolerant but the GPIO's setup for the i2c bus are,
and my connection to this i2c backpack & lcd is direct with no level shifting. The backpack/lcd are supplied from one of the the Pi's 5 volt pins (pin 2).

Reading from and writing to the device have been consistent for several weeks.

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Re^3: i2c lcd Custom Characters
by jmlynesjr (Chaplain) on Jun 11, 2016 at 19:09 UTC

    I don't have an RPI but it sounds similar to the Fubarino Mini which has about 1/2 of it's pins 5v tolerant, which also includes the I2C pins. The UNO32/uC32 is a 5v tolerant board at twice the size and a few dollars more expensive.


    There's never enough time to do it right, but always enough time to do it over...


      As far as I know, none of the Pi's pins are 5 volt tolerant, it is only when configured and used with the i2c bus that they are tolerant.

      If these same pins were reconfigured to general purpose use, they would not be 5 volt tolerant.

      I think that the issue is the way that the i2c bus operates and how it is pulled up/down.



        Thanks for the info. Something to pay attention to if I ever decide to play with the RPI. It's starting to become popular in Ham radio circles.

        The Digilent docs state that the PIC32 digital I/O pins are protected but the analog I/O pins are not. Digilent adds protection diodes for the analog pins on their UNO32/uC32 boards.


        There's never enough time to do it right, but always enough time to do it over...

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