Best gyro for frc.

[connor.worley]

1538 had very good results with Analog Devices gyros.

[RyanCahoon]

I used a ADXRS453 for the NASA Sample Return Challenge this year and was impressed with the performance for the cost.

[Mike Bortfeldt]

I had a opportunity to test several different gyros (from two different manufacturers) on an FRC robot for a personal project and like the others, I would recommend the Analog Devices gyros. The one I am currently using is the ADXRS450 (similar to the ADXRS453 above - except without the internal temperature compensation) and it works well. If price isn't an issue, higher quality gyros are available with some excellent specs, however they typically run more than $1000.

Mike

[AustinSchuh]

Originally Posted by RyanCahoon

I used a ADXRS453 for the NASA Sample Return Challenge this year and was impressed with the performance for the cost.

We've been using that gyro as well, and it works incredibly well. Very low drift, very low acceleration -> yaw coupling.

[AdamHeard]

Originally Posted by AustinSchuh

We've been using that gyro as well, and it works incredibly well. Very low drift, very low acceleration -> yaw coupling.

2 years in on the same gyro for us, I wish we had used it with our swerve in 2012!

[Breakaway3937]

Originally Posted by AdamHeard

2 years in on the same gyro for us, I wish we had used it with our swerve in 2012!

Hey Adam,

I noticed that the pin out on these gyros are different from the KOP sensor board. How would you interface these with the control system we have with FIRST. I know you have to set up a SPI connection with SCLK, CS, MOSI, MISO, I just have no background with this.

EDIT: Found it. For anyone who wishes to know how to wire the ADXRS453. It is just like the accelerometer. You will take the SCLK, CS, MOSI, MISO to the DIO pins 1-4, doesn't matter really what order, and can power it from the 5V or Ground located below the DIO pin 1 location. Thanks all and hope this helps someone else out.

[seg9585]

I assume you use the SPIDevice class in Java (for example)? If so, can someone with experience using the ADXRS453Z provide feedback on the correct bit order, clock polarity, clock rate, and frame modes?

Any sample code you code provide would be helpful, which could help avoid hours of troubleshooting.

[scottandme]

This guy if you don't want to use SPI:

EVAL-ADXRS642Z - about $75 from mouser, digikey, etc

http://www.analog.com/en/mems-sensor...s/product.html

[AdamHeard]

Austin Schuh is really the best to answer those questions here.

Colin Wilson (254>973>254) made ours, and could also answer but he's less active on here.

[AustinSchuh]

This is on my over-booked TODO list...

We had a co-processor reading it last year. We are putting together a board right now to interface one with the roboRIO. We'll be releasing our beta test code closer to the start of the season. I expect that we should be able to interface with it over SPI.

[Aren Siekmeier]

Originally Posted by AustinSchuh

This is on my over-booked TODO list...

We had a co-processor reading it last year. We are putting together a board right now to interface one with the roboRIO. We'll be releasing our beta test code closer to the start of the season. I expect that we should be able to interface with it over SPI.

Austin,

Do you expect any differences between integrating on your co-processor and integrating with the accumulator in the FPGA, in particular with integral error and drift? What was the SPI bus clock speed/integral dt on your co-processor? Do you happen to know the SPI frequency on the roboRIO? (I think I saw 4MHz in a myRIO document...)

Thanks,
Aren

[AustinSchuh]

Originally Posted by compwiztobe

Austin,

Do you expect any differences between integrating on your co-processor and integrating with the accumulator in the FPGA, in particular with integral error and drift? What was the SPI bus clock speed/integral dt on your co-processor? Do you happen to know the SPI frequency on the roboRIO? (I think I saw 4MHz in a myRIO document...)

Thanks,
Aren

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

[Hugh Meyer]

Here is a nice one.

http://www.ebay.com/itm/291208070192...%3AMEBIDX%3AIT

-Hugh

[seg9585]

Originally Posted by AustinSchuh

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?

[seg9585]

Originally Posted by scottandme

This guy if you don't want to use SPI:

EVAL-ADXRS642Z - about $75 from mouser, digikey, etc

http://www.analog.com/en/mems-sensor...s/product.html

How reliable is this gyro as an analog voltage output? The gyro on the ADXL345 (FIRST Choice, etc) simply didn't work for us, it had way too much drift to be useful. A typical 2-minute match resulted in >45 degrees of drift! Because of this, I've become skeptical of analog sensors requiring integration for attitude/position calculation (too much noise on the A2D probably led to these problems)