I2C on Wipy 3.0 + extension board

  • Hello,

    I am trying to scan the I2C port on my Wipy 3.0 but I always get an empty list nomatter what I do.
    I found that many codes on the net are deprecated considering the new versions of Wipy.
    So here is what I did

    i2c = I2C(0, I2C.MASTER, baudrate=100000)

    Where should I plug the pins on the extension board.
    I did use G16 and G17 (which I assume are connected to P9 and P10 of the wipy).
    Am I wrong? Are the pins on the extansion board the same as the board itself? or are they somehow rerouted somewhere else???

    I tryed two different devices and yet did not get any address :(

    Does any one has an idea why this is not working?

  • @dr_aloui In that case it's strange. You you have an oscilloscope to look at the signal timing? The expansion board should not add any significant load to the wires, at least not to P9 and P10. The Pyboard has built-in pullup-resistors on the pins dedicated for I2C (X9/X10 and Y9/Y10). That could makes a difference.

  • @robert-hh The wires are not very long (around 4cm long). I tryed the same configuration with the same wires on a pyboard and I could use 400000Hz baudrate. Maby the extensionboard adds some extra capacitance on the lines but it really seams odd.

  • @dr_aloui It could be the RC time constant on the SCL/SDA lines, meaning R too high or C too high. Please check the Pullup-resistors. How long are the wires to the BN0055?

  • I started to figure out the problem.

    In my dispaire, I lowered the baudrate to a non I2C common baudrate of 9600.
    At this baudrate, the BNO055 responded to my scan and sent its address.

    I started rising the baud rate and try to figure when the baud rate is no more sufficient to talk with the BNO055.

    It crushed above 60000. I don't understand what is the cause of such problem.

  • I did buy another couple Wipy 3.0 and Expansion board. I connected the BNO055 breakout exactly the same way and tryed the scan and it worked.

    I thought it was a problem with one of the other boards until i realize that after updating the wipy 3.0 software to the latest version, The scan returns an empty list.

    It is defenetely linked to the software version. Is there any significant changes in the latest update of the firmware that cause this problmen???

  • I wonder if the problem is linked to the fact that the button and the led of the extension board are linked to these two pins.

    The datasheet of the bno055 breakout mensions the existance of 10k pullup resistors on its SDA and SCL pins so it is not a pullup problem.

  • I am trying to interface a BNO055 adafruit breakout.
    I tryed the same device on the pyboard, and the scan shows [40] which is the right address.
    I have a Wipy 3.0 + Extension 3.

    I don't have all my jumpers connected on the extension board.
    Are all your jumpers on?

  • @dr_aloui GPIO16 and GPIO17 works for me with a LoPy4 and Expansion3.
    What I2C devices?

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