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I2C interface voltage level

denisdarmondenisdarmon
in Hardware
I recently acquired a
metaMotionR. I would like to hook other I2C devices to the MetaMotionR board.
Those devices are already powered by their own 3.3V supply, and their I2C bus
is on that 3.3V supply. It seems the MetaMotionR IOs are on 3.0V. 
1. Are the I2C
SCL/SDA pins pulled up to 3.0V already or are they open? 
2. Can the MetaMotionR I2C interface support 3.3V signaling without damage?
3. Or, is a bi-directional level shifter required to interface the MetaMtionR to a 3.3V bus?


Thank you.
Denis



Comments

  • MattMatt
    @denisdarmon

    1.  The I2C pins are pulled up to 3.0V using bias resistors built into the BLE SoC.  Resistance is approximately 13k.
    2.  The MetaMotionR I2C interface can tolerate 3.3V.  There will be sufficient noise margin for correct operation of the signal lines.  The power supply design of MMR can also tolerate direct feeding of the 3.0V line from an external source, in which case the internal regulators will shutdown (though this may throw off the LED brightnesses).  However, feeding voltages higher than 3.3V risks damaging the device.
    3.  You should not need a level shifter to interface a 3.3V device with a MMR.

    You might also consider powering your 3.3V devices directly from the MMR's 3.0V rail.  Most devices designed for 3.3V should operate correctly at 3.0V.
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