So lately I have been messing around with the joystick accelerometer to make something with it, but the amount of bizarre noise that I get from it is absolutely ridiculous. You might be thinking "well, all sensors like that pretty much have a bit of random noise," which I know, but the noise I am talking about is a bit different.

I have done tests on the outputs of multiple joysticks, and all seem to have the same exact problem, problem being that they spike from 0 to extremely high values. I've taken data from a run of the accelerometer (with the controller sitting still) and plotted it in excel.



I've plotted both x and y on the same graph.
Frequently, the data from X spikes from 0 to 127 and -127, as well as frequently -81, sometimes -61 as well.
Y spikes from zero to -58 and -61.

Does anyone have a solid explanation for this? I've used the vex three axis accelerometers, which have understandable noise, but the joystick accelerometer values just seem like a mess...

Any ideas or explanation is welcome. Thanks!

We have around 20 joysticks that we use for training. Three or four of them get spikes in data similar to what you're seeing, while others behave pretty well. I don't have much insight regarding why this is the case, but I've heard of some folks applying low and high filters, or a "Kalman" filter to help normalize the data.

Hope this helps with your project:
http://en.wikipedia.org/wiki/Kalman_filter
http://snippets.dzone.com/posts/show/11215

Could you not apply some kind of median filter to this?

- Xander

I don't think that would work by itself. Look at the space between 15000 ms to around 17500 ms. The values are all very negative even when the sensor isn't moving.

Yeah, I decided to try that simplified Kalman filter,
I'm implementing it now.

I'll take some values and see how stable it is once I do.
Maybe even a graph. I like to graph stuff.

If you do get it working with the Kalman filter, you could help a lot of people by publishing your code. Which is what "Co-opetition and gracious professionalism" is all about

- Xander