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FXOS8700 accel transient threshold resolution in per-axis mode

Question asked by Nick Vallidis on Mar 26, 2015
Latest reply on Apr 8, 2015 by Tomas Vaverka



I am using the FXOS8700 with the accelerometer transient detection feature. The data sheet shows two ways to set the threshold:

  1. Use TRANSIENT_THS which has a resolution of 63 mg/LSB and the same threshold would be used for all axes
  2. Use A_FFMT_THS_* by setting high bit of A_FFMT_THS_Y_MSB and then you can set per-axis thresholds


What is the resolution of the A_FFMT_THS_* registers when they are used to set the threshold? From my tests, it looks like it is also 63 mg. The lowest two bits of each register aren't used so the values have to be shifted left by two bits, but otherwise it appears that the resolution is also 63 mg? I can't find specific mention in the datasheet and I have to admit I was hoping for a higher-resolution threshold so that it could be set lower than 63 mg.