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Unread 09-02-2017, 12:50
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Omar Zrien
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Re: Recommended gyros that can keep up with fast rotation?

Quote:
Originally Posted by slibert View Post
Pigeon update rate is 100hz, navX-MXP/navX-Micro are 200hz, so if you want faster update rate the latter is superior. 200Hz is great if you want to drive rapid PID loops that manage the orientation of multiple wheels on the robot.
We could probably do 5ms. In all honesty when I started with the Invensense example, it was set to 10ms, and I just never tried changing it.
Originally I was planning on using a different IMU chip entirely but then we couldn't source it in time, I had to switch. In so doing I just left all the timing the same as the previous IMU.

If you guys think that's an important improvement, we'll add it to the list.
In my testing the update rate seemed adequate so I didn't dig further.
Quote:
Originally Posted by slibert View Post
We will have to see if there's any CAN bus contention limits the Pigeon IMU from consistently achieving update rate at 100hz, CTRE should be able to say on that.
This is not a problem. Pigeon only adds ~6% CAN bus util whether it be CAN or gadgeteer.(Section 11.4).
Quote:
Originally Posted by slibert View Post
From a software perspective, the Pigeon docs indicate it provides yaw, pitch and roll - however the navX-MXP/navX-Micro also (perhaps because it's not limited to the 8-byte CAN bus data payload sizes) provide synchronized quaternions and a sensor timestamp as well.
If you guys think that's important, we'll add it to the list.
In my research none of teams seemed to care about time-synchronization.
Maybe most teams just "aren't there yet". But if a bunch of teams start asking for it, we'll probably implement. Synchronizing signals across CAN frames is something we know how to do.

All in all there are many options for good nav, including NavX [and Pigeon ].
Inertial navigation has been a hole in our product line for a while, so I was eager to fill it. I think what makes Pigeon unique is the on-the-fly temperature compensation, multiple connection strategies, robustness against power-dips, fast boot-cal, price, and future features where our CAN devices work together.
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