Re: Example gyro code released.
 

Where did you hear they are illegal? Check the Q&A under ID 1118:
EDIT: Nevermind... I guess the Q&A people didn't look up the price...

Re: Example gyro code released.
 

Sweet, thanks for the info. I was under the impression it was illegal seeing as it was up for sale in a FIRST yard sale.

Re: Example gyro code released.
 

I've updated the gyro code to include scaling factors for the two different BEI GyroChip gyros that FIRST has included in the KOP in the past. The code can be found here: http://kevin.org/frc.

-Kevin

Re: Example gyro code released.
 

I don't believe that the BEI gyro's are legal because the lowest price I have been able to find them for is approximately $350 which over the $200 price limit for additional electronics. If anyone has seen a gyro for sale cheaper then that, that would follow the vendor requirements that FIRST has laid out please post a link because I have 3 of them sitting in the shop that I would love to use on this years robot.

Re: Example gyro code released.
 

Hmmm..Magic?...We tried to calibrate the gyro, but there was too much drift. We mounted it to a square piece of wood, but we still had too much drift. Is there any way to control the drift?

Thanks

Re: Example gyro code released.
 

What kind of gyro are you using? Did you try the manual method that uses Set_Gyro_Bias()? Just make sure the gyro is motionless as the bias is being calculated.

-Kevin

Re: Example gyro code released.
 

We are using ADXRS300ABG & ADXRS300EB-ND Gyros. Yes we tried the manual method that uses Set_Gyro_Bias()?

Re: Example gyro code released.
 

How much drift are you seeing (you need to calibrate the scaling factor first).

-Kevin

Re: Example gyro code released.
 

Ok, I just looked into this as well and you're right. The darn things are too expensive! (now we need to buy a new gyro..)

Edit: Actually, on second thought, does anyone know for sure if the fact that FIRST gave it to us in previous years makes a difference?

Re: Example gyro code released.
 

The values for "rate" and "angle" are empty in the terminal window. Once in a while, "angle" is 0. When we manually set Bias, the values for "rate" and "angle" are gibberish...Also, sometimes, the dreaded "windows fatal error" screen comes up. We have followed the steps that was in the readme.txt file. And no changes to the code were made...except for, changing to the right gyro model #.

Re: Example gyro code released.
 

I think you'll need to find a different windows machine to use before you'll be able to make any progress.

-Kevin

Re: Example gyro code released.
 

Hey, thanks. We got it to work. We took it to a "quiet" place, and it worked fine. Maybe its those machines that messed it up...

Re: Example gyro code released.
 

We used the code with the ADXRS300 as well and were seeing about 8 degrees of drift over 2-1/2 minutes on a motionless robot. We modified the code to average the bias over more than a single group of samples and increased the sample size to 16 to get the extra precision. That seemed to improve the results.

Can you tell us what you were seeing for drift over time? I just wasn't sure what to expect for results and so we tried these modifications.

Also, I have a question. You're locking the A/D onto Channel 1 to presumably eliminate that acquisition time when switching channels. How much time does actually take (for teams that want more than one analog input)?

And do you know what the conversion time is once the channel is switched?

Thanks again for posting the code.

Brad

Re: Example gyro code released.
 

Without actively tracking the bias, you're getting performance that is about what I would expect from a ADXRS300. I'd be pretty happy with a gyro that only drifted a degree over the entire autonomous period. For reference, I have a ADXRS150EB that drifts a degree over about a minute and I tested an old GyroChip that did even better.


No, I take control of the ADC hardware because I'm trying to be pretty efficient and not use up a lot of CPU time. You'll notice that in response to the timer interrupt, I read the ADC result register and then immediatly start another conversion. If you used the ADC after my conversion was done, I'd have lost the conversion result the next time the timer interrupt fires off. One way around this is to increase the timer interrupt rate and interleave the ADC measurements.


I'm sure it's considerably less time than the timer interrupt period, but I don't know the exact value. The data sheet would be a good document to consult for this information.

-Kevin

Re: Example gyro code released.
 

Is it possible for us to use the ADC for say.. another gyro?