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Unread 22-12-2014, 16:06
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seg9585 seg9585 is offline
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AKA: Eric
FRC #4276 (Surf City Vikings)
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Re: Best gyro for frc.

Quick update for anyone interested in using a reliable gyroscope this year:

I purchased the EVAL-ADXRS453Z from Mouser and wired it up + tested on an Arduino this weekend.
Overall I got great results! There was a rate bias (0.417 deg/sec) but when I nulled this out, the bias change was minimal.
I programmed 1 kHz sampling with a 50-sample smoothing which fed into my integrator to calculate heading.

Results: I achieved a maximum heading drift of approx 0.35 degrees/minute. This is highly acceptable for FRC given 2-2:30 minute match lengths.

A few notes:
The Gyro SPI clock runs at up to 8Mhz. My Arduino is capable of 16Mhz but the roboRio can only output 4Mhz. Anyway, I verified the drift was still acceptable when running the Gyro at 4Mhz.

The data is 32-bit MSB, zero polarity and requires Chip Select to be pulled low for data collection.
Rate data is 16-bit and is stored in Registers 25 through 10 as two-complement, so a little bitshifting and data conversion is required.

I plan to implement this with the FRC Java SPIDevice class and will let you know if it performs as well as it is with the Arduino.
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Team 204 Student 2001, 2002 (Voorhees, NJ)
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