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January 2, 2010
about 4 years ago
Hit me up at firstname.lastname@example.org and we’ll go from there
Yes, I got the acceleration feature to work. The only time you will see zero acceleration is when the unit is in free-fall (or in space). Otherwise, it shows the acceleration due to gravity (1g = 255). This lets you use the accelerometer as a tilt sensor, but if you know orientation you can subtract out gravity to get just local acceleration.
I believe that “$PLSR,245,2” returns a 3x3 rotation matrix representing the attitude of the unit, of the following form:
att = [ [Xx Yx Zx]; [Xy Yy Zy]; [Xz Yz Zz] ]
If you treat this matrix as a composition of simultaneous yaw, pitch and roll rotations about the inertial frame, you can back-calculate the angles. When I did this, I found that yaw was unspecified (which makes sense), pitch gave a good value but only when there was no roll, and roll gave a somewhat nonsensical value. Perhaps I am just not understanding how they formed the attitude matrix.
How did you get it to auto-calibrate?
Bought this, wired up to the pads and got it working without trouble. I took it out to an open field at night and did a 20-minute static data collect (not moving it). The mag looked pretty good, I’d say +/- 2 degrees noise and no drift, but the GPS was terrible - over ten minutes my position drifted 30m in one direction then over the next ten minutes it drifted 60m back the other way (noise was just a couple meters though). I don’t have any other modules to compare with, so it could have been atmospheric effects for all I know, but I would love to hear what kind of long-term stability people see with the other modules.
The accel is a pretty neat feature, but kinda useless at 1 Hz. The data sheet makes it sound like 5 Hz output is possible - anyone know how to do this?
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