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Thread: I2C question on Teensy 3.6

  1. #1
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    I2C question on Teensy 3.6

    I plan to connect a sensor board, communicating over I2C and operating at 3.3 VDC, with a Teensy 3.6 via the SCL0 (pin 19) and SDA0 (pin 18) ports.

    The only hookup documentation I have on that board shows the connection with an Arduino UNO board.

    Since the I2C comm ports (SCL, SDA) for the UNO operate in the 5.5V range (per this documentation), these 2 connections with the sensor board require each a 330 ohm resistor.

    From what I gather, the Teensy 3.6 operates at 3.3 VDC. So, I am assuming that the resistors are not required.

    Appreciate feedback on whether the resistors are needed with the Teensy 3.6.

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Well it would help if you mentioned which sensor you are trying to hook up to the Teensy.

    You will need two pull-up resistors for the Teensy. Typical values on a Teensy would be 2.2K to 2.4K. You hook one resistor between SCL and 3.3v and the second one between SDA and 3.3v. The Arduino UNO does not need pull-up resistors, but the Teensy does.

  3. #3
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    If your sensor board really wants 5V I2C, take a look at this: https://www.adafruit.com/product/757

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by digysol View Post
    Appreciate feedback on whether the resistors are needed with the Teensy 3.6.
    Teensy 3.6 requires pullup resistors connected between the I2C signals and 3.3V.

    With Arduino Uno these resistors are optional (and would connect to 5V). With Teensy 3.x they are mandatory, and need to connect to 3.3V.

    Most sensor boards from Adafruit, Sparkfun and others have the resistors built in. If you had mentioned the specific board you're using, we could have looked at its info and given you specific help. But you decided not to tell us exactly what hardware you're using, so this generic info is what you get.

    The resistors must be used.

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