BNO080 IMU is not starting, why ?

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
Hello,
I made a board with the BNO080 on it. I attached the schematic.
I already tried 3 chips, all of them didn't work. I was careful to not use too much heat. My heat gun was set on 250 degrees celsius max.

I purchased a known good board from Adafruit and measured the clock output. It shows a 32kHz clock as expected, but my board doesn't have this. It's only outputting a constant DC offset. This problem bugs me for a while now, and I'm running out of ideas.

If anyone has ideas I could try, hit me with it, I'm desperate.

-8
 

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AlbertHall

Joined Jun 4, 2014
11,317
For I2C communication, PS0 and PS1 should be grounded. I couldn't find, in the datasheet, what happens if these pins are allowed to float.
 

AlbertHall

Joined Jun 4, 2014
11,317
Do you have pull-up resistors on SDA and SCL?
SA0 should be pulled either high or low - again I don't know what would happen if they were floating.
 

AlbertHall

Joined Jun 4, 2014
11,317
BTW measuring the oscillator by connecting a 'scope probe to the crystal pins will not necessarily give you meaningful readings as the capacitance of the probe can be enough to stop the oscillator. You would have a better chance using a X10 probe but still no guarantee.
 

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
Yes I have pulled both with 4.7k ohms on each high.
Thanks, I have pulled SA0 low to set the address to 0x4A.

Yes I have tried it with a 10x probe.

But still, none of the changes made it work so far :/
 

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
I have written software for the chip by using the mentioned known good board. The only thing the software assumes is that the I2C address is 0x4A. Which should be no problem. After that everything happens over the I2C.
 

AlbertHall

Joined Jun 4, 2014
11,317
The software works OK with the adafruit board?
Is your circuit built on a PCB - in which case show us the board layout (both sides if it is a double sided board.
 

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
Yes, the software works with the Adafuit board.

On my breakout board I had everything broken out except for the SA0 pin. So I soldered a thin wire to it, but I suspect (since it's an LGA package) the wire pushed the chip up and the connections next to it weren't sound enough. I will deadbug the chip now, and if that's not doing the job I will post a picture of it and the board files.
 

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
Alright, it worked :D (I'm almost certain that the connection on the previous attempts werent good).

I connected everything as we discussed before, but for one thing. I used the internal clock. Also, I attached some pictures of final thing.

Thanks for the troubleshooting @AlbertHall
 

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AlbertHall

Joined Jun 4, 2014
11,317
If the BNO080 is on the board with the red arrow and the crystal and 15p capacitors are on the board with the green arrow then I am not surprised it didn't work. That length of wire connecting the oscillator to the chip is not going to work properly.
218161-6d376ac5c652740191c67224cad7c235.jpg
 

Thread Starter

8dm7bz

Joined Jul 21, 2020
199
No, that is only my setup for the use of the internal clock of the BNO080.
I will attach the board where I had problems with, using the external crystal. But on that board I tested 2 sensors (black circled is the BNO080 section). And the pruple area is the crystal.
Green is the SA0 pin, which I didn't break out.
 

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