Hello!
I know, that the sensor is a little bit old, but nevertheless.
I have one application case and I still cannot solve a problem with transient detection. Of course I have read all App. Notes.
Use case description:
- Sensor board attached to the wrist so that x-axis is along the arm (if we stretch index finger - the x-axis and the finger are +/- parallel).
- The arm is on the rest (Xg =~ -250mg). It is initial position.
- Now the stretched arm will be rosen slightly above the head (Xg =~ 300-350mg).
X and Z axes are ignored (out of interest). - I want to have an interrupt after hand was rosen as described above.
Here is described motion (ODR=100Hz)
My first idea was to use vector-magnitude detection. But I did't tried it because I don't have constant Gref (initial position may have some variiations...).
The second idea - motion or transient detection.
Code (abstract):
- software rest + 1ms wait
- Standby CTRL_REG1=0x0
- Fullscale 2g XYZ_DATA_CFG=0x0
- Clr debounce counter and set ths to 5 (5x63mg=315mg) TRANSIENT_THS=0b10000101
- TRANSIENT_COUNT=6
- X only + evt latching TRANSIENT_CFG=0b00010010
- Enable transient interrupt CTRL_REG4=0b0010000
- Route transient interrupt to int1 CTRL_REG5=0b00100000
- Active mode, ODR 12,5Hz, Low Noise CTRL_REG1=0b00101101
Interrupt event triggered non-stop. I tried many different values for 4) and 5).
uC input IO configured for neg. edge with enabled pull-up.
I tried to move 6) after 3) like here. No interrupt triggered at all.
I tested circuit enabling FIFO watermark interrupt. Works without problems.
Any ideas?
Or motion detection is more suitable in my case?
Many thanks in advance
Hello Igor,
for your case, I think the best would be the "Acceleration vector-magnitude detection". Please refer to the section 12.10 in the FXOS8700CQ datasheet and to the AN4692.
With Best Regards,
Jozef
