I am using the FXOS8700 as an e-compass and of the first 10 prototypes, we have found that on one the accelerometer z axis never changes. On several others the accelerometer z axis is intermittent. I did not experience this with the 5 sample chips I tested last spring. I'm using the same code as before. I tried setting the self-test bit in CTRL_REG_2 and again, the z axis never changes. The value read is always 0x1FFF (raw value of 0x7FFC). I am using hybrid mode, normal read, and am reading out 12 bytes (I2C) for each reading starting with register OUT_X_MSG. When the accel z axis is working, the compass works very well.
Has anyone else experienced this issue?