I have been trying to set up the BMA421 motion sensor in a nrf52 based smart watch, using the datasheet for the BMA423, which has the same interface. I had got the sensor working well with the original source code, but I was trying to set it up myself. It is connected via I2C, address 0x18.
I made some mistakes in my original code. I was trying to initialise the chip with a 6Kb byte stream (as in the original source), in chunks of 64 bytes. I didn't resend the register at the start of each data chunk, so ended up writing bytes to random registers.
Unfortunately, I have managed to get the sensor into an unrecoverable state - it now returns 0xFF to all reads, and doesn't respond to a soft-reset code (register 0x7E=0xB6). Even exhausting the watch battery to power cycle the chip doesn't seem to help.
I have found someone with a similar issue on the Borsch Sensortec forum, so I am hoping that a complete battery discharge works.
Does anyone have any other suggestions?