Difference in behavior between BHI360 shuttle board and custom BHI360 board

[elie]

Hi,

I have successfully used the BHI360 shuttle board with an STM32 (through level converter).
BHI360 seem to match our needs.

I have therefore made a custom BHI360 board, but I cannot make it work (please find attached the schematics of the board)

We are using SPI at low frequency (~2MHz)

Some differences I have seen, between custom board vs shuttle board :
- product_id = 0x80 instead of 0x89
before upload
- boot_status = 0x10 instead of 0x18
after upload to ram
- boot status = 0x3F instead of 0x38

bhy2_boot_from_ram fails with error BHY2_E_TIMEOUT
firmware is BHI360_Turbo.fw.h
I use BHY2_SensorAPI from github

The BHI360 comes from reliable suppliers (mouser).

Any idea that would explain why I cannot make standalone BHI360 work, but have no issue with the shuttle board ?

I'm at a loss

Thanks

[elie · Accepted solution]

Found it. I was using slow level translators with the shuttle board, and fast ones with my custom board.

It seems that the load capacitance of BHI360 SPI pins was too low for the 74LV125T1 and things were ringing. Connecting an oscilloscope probe would fix it.

For now, I have "fixed" the problem with 10pF (edit : 32pF) in parallel with BHI360 pins.

BHI360 is working without any issues now, I'm just puzzled by this behaviour 🙂