BNO085 - Bringup

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Joined Jul 21, 2020
I tried to breakout the BNO085. I used a known good design from Adafruit (attached the schematic). Now unfortunately it doesn't work. I written software for the Adafruit board and it works fine. Then I replaced the Adafruit board with my breakout board ("schematic_not working" in the attachments).

I made a few measurements and compared it to the Adafruit board. I found some differences, but can't make sense of it.
1. Pin 14 is an interrupt pin. So it goes high when the BNO085 needs attention. On the Adafruit board that pin is 3.3V. On my breakout board it is at 1.2V ish.
2. When I measure the 32.768 kHz capacitors, I get a clock signal on the Adafruit board. But when I do the same thing on my breakout I get some DC offset.

Based on that I figured that the clock is not working, and therefore the BNO085 outputs nonsense on the interrupt pin. Now I don't know if that's correct, any thoughts on that would be appreciated.

Also I want to hook up my function generator to the clock input. But since I never did such a thing I would like to ask on which pin and how the wave should look like(sine/square, amplitude).

Any thoughts about how to make it work, are appreciated.

UPDATE1: It doesn't appear to be the clock. I pulled pin 10 high and pin 26 low as it says on page 12, to enable the internal clock. But it's still not working.


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