I have checked pin 15, 16 could be DNC in schematic.
On my side, I tested it on BNO055 shuttle board, MCU could receive I2C ACK.
BNO055 shuttle board schematic: https://www.bosch-sensortec.com/media/boschsensortec/downloads/shuttle_board_flyer/bst-dhw-fl039.pdf
One point needs to be checked on your HW board is oscillator circuit. Please ensure you could boot BNO055, and then test if I2C communication is ok. Please firstly check their crystal oscillator circuit and fine tune the load capacitor.
Refer page 110 of BNO55 data sheet: https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bno055-ds000.pdf
Thanks for the response, but the issue is more fundamental than the Xtal.
As stated at 5.5 of the datasheet, the internal clock is used by default, and you can only switch to the external crystal by setting the CLK_SEL bit via I2C bit - so I2C must work even if the crystal circuit is broken.
I don't get any ACK from I2C, even from startup.
I'll keep trying to figure it out (if I can find somewhere to buy a few more parts!!)
I don't believe we have a soldering issue bacause:
- We have 15 boards that all behave the same.
- These were machine built and we have other LGA parts that are well connected.
- I took one part off and could see that all solder pads had been connected.
Is there anything else that could cause a noACK ?