BNO055 not responding to UART

[manag]

Hello

We have a problem with an UART configuration.

We have an entire batch of 6 boards that have been designed as-per the following schematic (see both datasheet, and actual schematic) that does not work.

We provide a UART command using 115200 8N1, but the BNO055 COM0 pin (UART_RXD signal or P87 in our schematic) is always low. We have isolated that signal (cutting R361) to see if the MCU was driving it low, but both sides of the resistor read 0V even then.

In a desperate effort and to discard the microcontroller, I have isolated my on-board BNO055, and attached with 4 wires (VDD, GND, TX, RX and PS0/PS1 for UART) an Adafruit BNO055 board, and it answers to commands correctly.

What is wrong with my schematic? It is as per the latest BNO055 datasheet, as far as I am concerned. I notice that PIN15 and PIN16 are DNC, but I saw another appnote where they are tied to GND, and even in the Adafruit BNO055 board they are tied to GND (along with pin 10, which in my case is DNC), and the system works with this board.

Thank you

[manag]

We have a problem with an UART configuration.

We have an entire batch of 6 boards that have been designed as-per the following schematic (see both datasheet, and actual schematic) that does not work.

We provide a UART command using 115200 8N1, but the BNO055 COM0 pin (UART_RXD signal or P87 in our schematic) is always low. We have isolated that signal (cutting R361) to see if the MCU was driving it low, but both sides of the resistor read 0V even then.

In a desperate effort and to discard the microcontroller, I have isolated my on-board BNO055, and attached with 4 wires (VDD, GND, TX, RX and PS0/PS1 for UART) an Adafruit BNO055 board, and it answers to commands correctly.

What is wrong with my schematic? It is as per the latest BNO055 datasheet, as far as I am concerned. I notice that PIN15 and PIN16 are DNC, but I saw another appnote where they are tied to GND, and even in the Adafruit BNO055 board they are tied to GND (along with pin 10, which in my case is DNC), and the system works with this board.

Thank you

[BSTRobin]

Hello manag,

Pin 15, 16 could be connected GND or be DNC.
Has the crystal oscillator of the six fast circuit board started? You can check it with an oscilloscope.
This is official shuttle board schematic,https://www.bosch-sensortec.com/media/boschsensortec/downloads/shuttle_board_flyer/bst-dhw-fl039.pdf

[manag]

Hello

The oscillator is not starting, I have plain 0V in both XTAL lines.

- I have tried to pull reset to GND and then release it (with a cable) but the oscillator does not start.

- I removed the XTAL and he capacitors in one of the boards and the BNO055 behaves exactly. 

- Parts: Crystal is ABS07AIG-32.768kHz-T. Capacitors are 06035C220JAT2A (22pF)

Hope this helps.

Thank you

[BSTRobin]

Hello manag,

The BNO055 can run from an internal or external 32 KHz clock source. By default, the internal clock is selected. Normally, serial communication can work even if crystal vibration is not up.

I tested it with BNO055 shuttle board, https://www.bosch-sensortec.com/media/boschsensortec/downloads/shuttle_board_flyer/bst-dhw-fl039.pdf

 PC software send UART command to BNO055, reading chip ID UART command got correct response.

I think the following two aspects should be examined:

1.Check whether MCU could work normally?

2.Check whether the welding is normal?

[manag]

Hello

Connecting an Adafruit BNO055 board works.

The onboard device does not work. 

Any other idea? Bad silicon or damaged silicon?