Wouter van Verre's Posts (1)

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Developing an IMU from the UAVDevBoard

Hi all!

First I wanna congratulate all of you with all the things you've achieved already!
Now I have question:
I have to do a large school project, I have almost a year to complete it, and I want to make an IMU and display the data graphically using a rotating cube. I've done a lot of reading on this site already, and this is what i came up with:

My idea is to use the UAV Dev Board as a starting point. I would make my own board based on the UAVDevBoard, and rewrite the code (Yes I know I'd be reinventing the wheel, but thats part of the assignment :P).
Because the IMU would not be moving a lot, I won't be able to use GPS data for yaw correction (Right?), so I would need to use a magnetometer (Right?). And if so, what kind of magnetometer would I have to use? I was thinking a 3-axis tilt-compensated magnetometer like this one: http://www.sparkfun.com/commerce/product_info.php?products_id=8656

Also the sparkfun description of the UAVDevBoard kind of confuses me, because it says
"dsPIC runs at 120MHz with 16MHz resonator and PLL"
Now I understand that PLL can multiply the clock speed. But my understanding is that it can only multiply by 4, 8 or 16, none of which give 120MHz. Also the datasheet says that PLL can only be used with a 4-10MHz oscillator.
And finally, in the code i can't seem to find the place where the PLL is set?
Could someone maybe explain to me how they got to 120 MHz?

With regards,
Wouter van Verre
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