Accleration of Vehicle (FXOS8700CQ)

[evanvaughan]

Hello

I am using the FXOS8700CQ to check whether a vehicle is moving. My main Problem is, that i don't know the orientation of the device when installed in the vehicle, so i can't just enable only the x-axis. The device may also be installed diagonaly, so just figuring out which axis to disable doesn't seem to work either, since Forward acceleration value could be a combination of two or three axes.

The aim is, that an Interrupt is triggered when the device starts moving, and another one when it stops. After some testing i think this can be achieved with de debounce Counter in-/decrementing with every cycle with an Interrupt on both edges.

I'm glad for any ideas as to how to solve this Problem.

Regards,

Evan

[darioarias]

Hi Evan,

The FXOS8700CQ already has an embedded functionality for motion detection, motion detection is often used to alert the main processor that the device is currently in use. When the acceleration exceeds a set threshold for a set amount of time, the motion interrupt is asserted. You just have to configured threshold and timing values for the event. There is also directional data available in the source register to detect the direction of the motion that generated the interrupt. So, no matter how that you don't know the orientation of the device when installed in the vehicle, you can set the threshold for all the axis. You can find more information about this in the datasheet in section 12.6 and 14.9.

Darío