We have just designed a board with BNO055 on it. As per the datasheet (Rev 1.7, Nov 2020), we left pins 15,16 "DNC" - unconnected. On powering up the board, the BNO055 does not respond to I2C commands (no ACK to slave address). We had previously prototyped the system using 3rd party BNO055 eval boards, and it worked fine. The only difference we can spot is that pins 15 and 16 are connected to GNDIO on every eval board we can find. We see the datsheet also used to have these pins connected to GNDIO, but it got updated in Rev 1.6, Feb 2020. There was a firmware update also just before this. The ICs on our board may be several years old, so might it be possible that the older firmware in these does actually need pins 15 and 16 connected to GNDIO?
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