BNO055 startup problems

[jontrausti]

Hi,

I've a bit a problem with some of our productions units. They sometimes report an init error due to the IMU not responding to our UART commands. After power cycling it becomes responsive. 

I have not been able to recreate this on a desktop setup, therefore don't have any logic analyzes log of the communications - can attach normal behavior if requested. Mostly wanted to see if you had seen this before or have an idea where the problem is. 

Thanks, Jon

[BSTRobin]

Hi jontrausti,

After schematic review, there were two comments:
1.Pin 15, 16 is not recommended to be connected.

2.You can check whether there is a 32.768KHz clock waveform on pins 26 and 27.

[jontrausti]

Thank you for quick reply! I've scoped the external clock and it seemed to be fine, was firmly oscillating at the correct frequency with no noise. 

Do you have more information about the updated recommandation on pin 15 and 16? This recommandation was updated after the board was designed, prior to the update the recommandation was the connect it to the GND.

Or can you link me to a errata documentation that can explain it? 

[BSTRobin]

Hi jontrausti,

The information that pin 15, 16 should be DNC was from BNO055 data sheet.

You could also find schematic in BNO055 shuttle board: https://www.bosch-sensortec.com/media/boschsensortec/downloads/shuttle_board_flyer/application_board...

[jontrausti]

Hi BSTRobin, I am fully aware the current recommandation is to have pins 15 and 16 DNC. The design we are working with is from prior to 2020 when the recommandation was to have it connected to GNDIO. I find it really bad support if you cannot explain the reason for the change. Therefore we cannot evaluate the importance of it - I am not gonna recommand to my HW guys to roll out a unnecessary revision update. 

Most MEMS companies I have worked with have released an errata explaining the errors occuring, why haven't Bosch SensorTec done so?