MMA8563 about Collision detection algorithm or application

[qlzeng]

MMA8563 chips were used to detect the car collision events in my system.Questions as follows:

1. the rate of false positives is higher,

2. do you have this aspect of the application or algorithm,Or do you have any Suggestions,

3. We can only download AN4083 document,other documents can't download, if you can provide?

My information:

E-mail:364656080@163.com

[bryce]

To get more information on the functions described in the app notes you can find the same information in reference to the MMA8452QR1 device.  The features are very similar between the devices so you can use this as reference material.

Here's the link:

±2g/±4g/±8g, Low g, 12-bit Dig|Freescale

[qlzeng]

Step 4: Set the debounce counter to eliminate false readings for 100 Hz sample rate with a requirement

of 100 ms timer.

Note: 100 ms/10 ms (steps) = 10 counts

My Questions:

1. DBCNTM bit configuration is not very understanding?Aimed at the two configurations

in the AN4070, you see if I understand correctly.

1) Motion Detection with ELE = 0, OAE = 1

       if DBCNTM=0, Once EA = 1 ,motion event have happened,but the debounce counter doesn't work.  the EA bit is cleared as soon as the motion high-g condition disappears.

       if DBCNTM=1, Once EA = 1, motion event have happened,until the EA bit can get cleared only after the delay specified by FF_MT_COUNT

2)Motion Detection with ELE = 1, OAE = 1

   Once the debounce counter reaches the threshold, the EA bit is set, and remains set until the FF_MT_SRC register is read.

Therefore, I think this plan "2)" is reasonable.

->When we set the acceleration range (2 g, 4 g, 8 g), how to and match them with the movement of the acceleration (8 g).

->Motion Detection and Transient Detection two methods, which a method to detect the car collision is better.

[qlzeng]

Thank you for your advice, I'll have a look at the related information.

[Martin35804]

Hi,

Regarding car collision events detection refer mainly to High-Pass Filtered Data and Transient Detection app. note no. AN4071. This one as well as the others are for the MMA845x family but do apply for the MMA856x family as well.

AN4071: http://cache.freescale.com/files/sensors/doc/app_note/AN4071.pdf?fasp=1&WT_TYPE=Application%20Notes&...

Other app. notes from the list but with different numbers can be found at following link:

±2g/±4g/±8g, Low g, 10-bit Dig|Freescale

As I have mentions the content of the app. notes applies for MMA8563  as well.