No Acknowledge from BNO055

Using Arduino Sensors
1

Arduino forum,
I have a BNO055 that when connected to an Adruino NANO works fine.

But if I try to address it with a pic18 I can't get an acknowledge.

Attached is a scope shot of an attempted write with no acknowledge.

I realize this is an Arduino forum but I was hoping someone here might know what I'm doing wrong.

Forgot to attach the scope shot. I'll do it in another post.

jerdon

2

Arduino forum,
Here is the scope shot I forgot to attach with m

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y post.

jerdon

3

I merged your second topic containing the scope image with your first one

I assume that you meant to reply to the first one and add the image rather than creating a new topic

4

Do you run Arduino code on the PIC18 ? Have you added a special "board" in the Arduino IDE ?
The Arduino Wire library uses the 7-bit shifted I2C address.
I think that is 0x28 in the scope picture. The BNO055 has 0x28 (or 0x29). But there is no acknowledge.

I don't know what is going on. I would look into these things:

  • Perhaps the scope is connected to the I2C bus and the sensor is not.
  • Perhaps the sensor is not powered.
  • Perhaps a jumper wire is broken.
  • Perhaps you use address 0x29 or a other mode for the sensor and forgot to put it back.
5

Koepel,
Thanks for the reply. All good points.

Didn't know it was possible to run Arduion code on a pic but it sounds interesting. Don't know about a special "board".

I have tried both 0x28 and 0x29.

I have measured the levels and buzzed out all the connections on the BNO055.

On page 91 of the data sheet it says "Both lines are connected to VDDIO externally via pull-up resistors so that they are pulled high when the bus is free." I tried putting 4.7K pull ups on the SCL and SDA pins anyway but that didn't work.

I'll attach a photo of my test fixture.

jerdon

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6

The BNO055 is a trouble maker. It needs clock stretching and does not always behave nice. I forgot what the trouble was, but there are known issues with the BNO055.

Can you add more decoupling capacitors ?
100nF, 100µF whatever you have. Add a number of them.

The Adafruit module is for 3.3V and for 5V. It has a voltage regulator and level shifters. Those are in the way.
The voltage regulator is the MIC5225-3.3 and has a voltage drop of about 100mV, because the BNO055 uses less than 1mA. That is not so bad.
The level shifters are mosfets. They make the signal weaker.
Suppose that you run it on 3.1V instead of 3.3V, then all those things together might cause trouble.

Perhaps the PIC18 has a timing problem that the scope does not show.

That is everything I can think of :thinking:

Solution: Get rid of everything. Buy a modern processor and a sensor that has no issues. When using a 3.3V processor, buy sensors without voltage regulators and without level shifters.

7

Koepel,
I tried several caps but they didn't help.

The input voltage is 4.15. One diode drop off the my 5v regulator.

I'm sure of the pic18 because I use this exact one for other projects and other sensors.

I'll look around for a better 9 axis break out board.

Thanks,
jerdon