in reply to i2c lcd Custom Characters

anita2R

I've also have had good luck talking(outputs) to 5v devices with a 3.3v Fubarino Mini. A (minimum)Logic high is usually around 2.5v so 3.3v will do the trick. You do have to make sure the RPI pins are 5v tolerant(inputs) so you don't zap an input pin. Level shifting could be required.

James

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

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Re^2: i2c lcd Custom Characters
by anita2R (Scribe) on Jun 10, 2016 at 19:52 UTC

    James

    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.

[reply]

      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.

      James

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

[reply]

        James

        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.

        anita2R
[reply]

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