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Thread: Two sensors can't work at the same time on Teensy 3.6

  1. #1
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    Two sensors can't work at the same time on Teensy 3.6

    Hello Everyone,

    I have a BNO055 and a barometer MS5611. I can get each to work with I2C connection. But As soon as I connect them to I2C at the same time. Teensy3.6 would lose their I2C address. The I2C scanner would no longer find anything, and re-connecting each will also not work. I have to "recover" each sensor on my Arduino Due, then magically they can't recognized on T3.6 again.

    What is going on here?? Any help, please

    P.s. BNO055 has internal pull-ups


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  2. #2
    Senior Member+ defragster's Avatar
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    With both connected and one having pull-ups, the external pull-ups should be removed AFAIK.
    Try a 'delay(1000);' at the top of setup() to allow the devices to fully power perhaps the Teensy is coming online and issuing commands too soon.

  3. #3
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    Your picture shows you are powering one with 5 volts and the other with 3.3 volts. I suspect this may confuse the I2C logic levels as you most likely have pullups to 5 volts and pullups to 3.3 volts. I suggest powering both sensors with 3.3 volts and see if that will work.

  4. #4
    Senior Member+ defragster's Avatar
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    Yikes - I didn't follow that 5V wire under and across - really not right since the T_3.6 doesn't have 5V tolerant pins.

  5. #5
    Senior Member+ manitou's Avatar
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    is this a duplicate of your earlier post ????
    https://forum.pjrc.com/threads/45630...-Raspberry-Pi-!

  6. #6
    Senior Member PaulStoffregen's Avatar
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    You might also check if your breadboard has the power connections all the way across. The ones PJRC sells are connected all the way. But some breadboards split the power bars into 2 sections. This can be very confusing, because you apply power to one side of the breadboard, but all the stuff on the other side does not get any power.

    I noticed the red and blue lines on the breadboard in your photo have a gap near the middle. That's a strong sign you may have one of those breadboards with split power rails. If you do, the the parts on the other side probably are not getting proper power, which would explain the problems you're seeing.

    To make matters even more complicated / confusing, some chips can sometimes (just barely) function with "parasite power" from a signals on their pins feeding a small amount of power through the ESD protection diodes inside the chip. If you have this sort of chip, the fact it sometimes works can cause you to assume it's getting power from the breadboard, when in fact it may be getting just barely enough power by stealing it from the signals which are connected.

  7. #7
    Senior Member+ manitou's Avatar
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    Quote Originally Posted by PaulStoffregen View Post
    You might also check if your breadboard has the power connections all the way across. ...
    Good catch! It looks like the sparkfun breadboard
    https://www.sparkfun.com/products/12615
    which has split rails. (maybe that limited the 5v damage )
    Last edited by manitou; 08-23-2017 at 07:14 PM.

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