I would like to share my experience with my new Turnigy GPS c/w compass. Actually the discussion is just about the compass. The trial is about me. So I hook the thing up and start polling the three axis values to the laptop. I can't tell much from the numbers streaming by but I do notice that something's not quite perfect here.
The X values are negative when the unit is pointing northish. And there's somthing odd going on with the Y values too. About the only thing that looks right is the Z axis. The Canadian Coast guard says, "by convention Z is positive downward", and they ought to know, right? And that's what I've got: large positive numbers for Z.
When I plot the X & Y vectors I see two real nice sine waves. But wait, they seem to be 90° out of phase. And sign reversed, of course. To cut a long story short, I finally got everything coming out normlly by swapping the X and Y values and changing the sign of everything is sight, except Z, because that's OK, right?
At some point, for no particular reason, and in spite of Z being OK, I find myself thinking of an old-time ship captain layin in his cot looking up at the "telltail" compass on the deckhead above, and I say to myself, "Oh no, they wouldn't".
I'm feeling myself slowly going crazy by now so imagine my unbridled delight when I finally take the thing apart and it becomes clear that they've mounted the compass upside-down on the bottom of the GPS pcb. Well that explains a lot; not the 90° thing, though. Imagine my exclamations of joy, then, when, on further inspection, it turns out they've chosen to flip the chip, not along the X axis, or even the Y axis, but diagonally. So it's both upside-down and twisted. Sigh.
Well, at least it's not me.
Cheers,
Colin
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