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Unread 29-10-2014, 19:19
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seg9585 seg9585 is offline
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Re: Best gyro for frc.

Quote:
Originally Posted by AustinSchuh View Post
Aren,

We integrated in software on our co-processor. Since the gyro is SPI, I'd recommend just doing the integration yourself in software on the roboRIO in a RT thread running at high priority. That's what we'll be doing. I like being able to audit the code, especially for something like a gyro where I've seen horrible bugs in the past. We got 2 ish degrees of error over 2 minutes with the ADXRS453.

I checked our uC code, and it looks like we read the gyro at 200 hz, and ran the bus at 7.5 MHz. 200 hz is above the gyro's bandwidth, which is good.

The roboRIO's maximum SPI clock rate is 500 KHz (as reported by WPILib's documentation.) The datasheet for the gyro lists the maximum clock rate to be 8 MHz, but doesn't list a minimum. This should be fine.

seg9585: This is a SPI gyro (digital). The ADC is inside the gyro chip, and seems to be very accurate from what I've seen.

Austin

Austin -- my reply was directed towards the recommendation of using the EVAL-ADXRS642Z, which appears to be an analog output.

I asked my questions earlier related to the ADXRS453 for which you provided at least some of the information I need to help initialize the gyro in the SPIDevice class. So thank you -- but I do have another question: the FRC-provided Gyro class performed a calibration within its Constructor that, to my understanding, calculated the drift bias it needed to apply to its integrator. It performed the calibration by taking a seconds-long sample of "still" data and averaging the values to find an offset. Did you have to perform a similar activity in your Robot Init method?
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