FXLS8971CF Variant? WHO_AM_I = 0x83 and Orientation Engine Non-Functional

[deanob]

I’m working on a custom board using the nRF52840 and integrating what was listed in our BOM and Digi-Key packaging as the #FXLS8971CF accelerometer. However, the device behavior and register responses suggest this may not be the part we expected

Observed Behavior:

• WHO_AM_I returns 0x83 (expected 0xC7 for #FXLS8971CFu
• Top marking on the chip is NXP 8900WYL
• Attempting to enable the orientation engine (SENS_CONFIG4 = 0x40) is ignored; readback returns 0x80
• ORIENT_STATUS (0x28) remains 0, even after active mode is confirmed and raw XYZ output is functional

Confirmed Working:

• I2C communication is solid (ret = 0)
• Raw acceleration data from registers 0x01–0x06 is accurate and changes with movement
• Sensor mode is correctly set to 0x13 (active mode, 12.5Hz ODR)

Questions:

1. Can you confirm what FXLS part corresponds to WHO_AM_I = 0x83?
2. Does the 8900WYL top marking correspond to an official FXLS variant (e.g. FXLS8962AF)?
3. Is orientation engine functionality supported on this part?
4. Could this be a masked-down or engineering sample?

[TomasVaverka · Accepted solution]

Hello Dean,

1. The correct WHO_AM_I value for the FXLS8971CF is indeed 0x83.

So this confirms that the device on your board does in fact identify itself as an FXLS8971CF accelerometer.

2. This top marking corresponds to an official marking of the FXLS8971CF. If you want to decode this marking/verify authenticity, please create a standard support ticket and provide again the full marking and your purchase source. 

3. Yes, orientation detection is supported on the FXLS8971CF as well as other FXLS89xx accelerometers. 

4. It is unlikely given that WHO_AM_I matches FXLS8971CF exactly, acceleration data is working. Orientation engine not working is likely due to misconfiguration, make sure the device is in Standby mode before writing to registers like ORIENT_CONFIG or ORIENT_THS.

BRs, Tomas

[deanob]

Hi Tomas, thank you for the help as soon as we wrote during standby it worked!

[deanob]