Chief Delphi - Gyroscope Code

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- - Gyroscope Code (http://www.chiefdelphi.com/forums/showthread.php?t=39537)

For those who might be interested, I've just posted updated gyroscope interface code for IFI's robot controllers. The code has been significantly reworked to use the new ADC interface code, which allows the programmer to use other analog sensors alongside a gyroscope without affecting the performance or operation of the gyroscope. In addition, significant performance improvements can be realized using the new oversampling and deadband features. The code can be found here: http://kevin.org/frc. As always, if you find a bug in the code or a problem with the documentation, please let me know.

-Kevin

Here's the readme file:

Code:

The source code in gyro.c/.h contains a driver and supporting 

software to interface a variety of inexpensive gyros to your

robot controller. This software was tested with Analog Devices'

ADXRS401EB, ADXRS150EB and ADXRS300EB gyros. Data sheets for 

these devices are included. By default, this software is 

configured to work with a ADXRS150EB gyro, sampling at 800Hz, 

downconverting to an update rate of 50Hz by averaging sixteen 

samples per update. These parameters can be changed by editing 

gyro.h and/or adc.h.

 

Version 0.5 of the gyro interface software has been altered

to use the ADC interface provided by adc.c/.h. This change 

allows the programmer to use additional ADC channels for other 

analog sensors without affecting the performance or operation 

of your gyro. See the documentation included with adc.c/.h for 

information on how to use this new functionality.

Another new feature is the ability to specify a measurement 

deadband centered about the gyro bias. ADC measurements within 

this deadband will not be used to calculate the gyro angle or 

angular rate. This feature can have a significant impact at 

minimizing short-term drift just after a bias calculation has

taken place. To use this feature, follow the instructions 

embedded within gyro.h.

 

This source code will work with the Robovation (A/K/A EDU-RC) 

robot controller and the FIRST Robotics robot controller.

Wiring-up the ADXRS401EB, ADXRS150EB and ADXRS300EB gyro

evaluation boards is straightforward: Grab a PWM cable and cut

off the male end and strip the three wires back a centimeter 

or so. With a low wattage soldering iron, solder the white wire 

to the RATEOUT pin, solder the black wire to the AGND pin, the 

red wire to the AVCC pin, and finally connect a jumper wire 

between the AVCC and PDD pins. Plug the female end into one of 

the robot controller's analog inputs. These gyro evaluation

boards can be purchased from analog devices (www.analog.com),

and Digi-Key (www.digikey.com). Another great source for

Analog Devices gyros is SparkFun Electronics (www.sparkfun.com).

 

For optimum performance, you'll need to calibrate the scaling

factor to match that of your gyro. One way to calibrate your 

gyro is to mount it very securely to a hefty, square or 

rectangular object. Mounting the gyro to a hefty object will 

help dampen higher frequency vibrations that can adversely 

effect your measurements. Place the mounted gyro against 

another square object and start the included demonstration 

software. To get good results, the mount must be absolutely 

still when the "Calibrating Gyro Bias..." message appears on 

the terminal screen. After a few seconds, the gyro angular rate 

and angle will be sent to the terminal screen. If the angle 

drifts rapidly while the mounted gyro is motionless, you need 

to restart the software to acquire a new gyro bias measurement. 

Again, gyros are very sensitive and must be still while the bias 

is calculated. Once the gyro is running with little drift, 

rotate the mount 180 degrees and note the reported angle. If the 

angular units are set to tenths of a degree, the ideal reported 

angle is 1800. If set to milliradians, the ideal angle 1s 3142 

(Pi times a thousand). For every tenth of a percent that the 

angle is high, decrease the GYRO_CAL_FACTOR numerator by one.

Conversly, for every tenth of a percent low, increase the 

numerator by one. Repeat until you're satisfied with the 

accuracy.

 

The included project files were built with MPLAB version 7.20.

If your version of MPLAB complains about the project version, 

the best thing to do is just create a new project with MPLAB's 

project wizard. Include every file except: FRC_alltimers.lib 

and ifi_alltimers.lib and you should be able to build the code.

 

****************************************************************

Eight things must be done before this software will work 

correctly on your robot controller:

 

1) The gyro's rate output is wired to one of the analog inputs

of your robot controller and gyro.h/#define GYRO_CHANNEL is

updated with the analog channel your gyro is attached to.

 

2) A #include statement for the gyro.h header file must be 

included at the beginning of each source file that calls the 

functions in gyro.c. The statement should look like this: 

#include "gyro.h".

 

3) Initialize_Gyro() must be called from user_routines.c/

User_Initialization().

 

4) You must select the gyro you're using from a list in gyro.h

and if needed, remove the // in front of its #define.

 

5) The default angular unit is milliradians. If desired, this

can be changed to tenths of a degree by editing gyro.h

 

6) A gyro bias calculation must take place using the functions 

Start_Gyro_Bias_Calc() & Stop_Gyro_Bias_Calc() described below.

This must be done several hundred milliseconds after the gyro 

powers-up and is allowed to stabilize.

 

7) For optimal performance, you'll need to calibrate the gyro 

scaling factor using the instructions above or those included

in gyro.h.

 

8) Follow the instructions found in adc_readme.txt for

installation instructions.        

 

****************************************************************

Here's a description of the functions in gyro.c:

 

Initialize_Gyro()

This function initializes the gyro software. It should be called 

from user_routines.c/User_Initialization().

 

Get_Gyro_Rate()

This function returns the current angular rate of change in 

units of milliradians per second. If desired, the angular unit 

can be changed to tenths of a degree per second by modifying

the angular units #define entry in gyro.h

 

Get_Gyro_Angle()

This function returns the change in heading angle, in 

milliradians, since the software was initialized or 

Reset_Gyro_Angle() was called. If desired, the angular unit

can be changed to tenths of a degree by modifying the angular

units #define entry in gyro

 

Start_Gyro_Bias_Calc()

Stop_Gyro_Bias_Calc()

These functions start/stop a new gyro bias calculation. For best 

results, Start_Gyro_Bias_Calc() should be called about a second 

after the robot powers-up and while the robot is perfectly still 

with all vibration sources turned off (e.g., compressor). After

at least a second (longer is better), call Stop_Gyro_Bias_Calc()

to terminate the calibration. While a calibration is taking

place, gyro rate and angle are not updated. Once calibrated, a

call to Reset_Gyro_Angle() should take place.

 

Get_Gyro_Bias()

This function returns the current calculated gyro bias. For

extra precision, this software internally maintains a gyro bias

value that is the sum of GYRO_SAMPLES_PER_UPDATE samples of the 

gyro's analog output. By default, GYRO_SAMPLES_PER_UPDATE is

set to a value of eight in gyro.h

 

Set_Gyro_Bias()

This function can be called to manually set the gyro bias. For

extra precision, this software internally maintains a gyro bias

value that is the sum of GYRO_SAMPLES_PER_UPDATE samples of the 

gyro's analog output. By default, GYRO_SAMPLES_PER_UPDATE is

set to a value of eight in gyro.h

 

Reset_Gyro_Angle()

This function resets the integrated gyro heading angle to zero.

 

Process_Gyro_Data()

This function should be called when the ADC software reports

that new gyro data is available. Ideally this should be done

within the user_routines_fast.c/Process_Data_From_Local_IO()

function. See the enclosed copy of user_routines_fast.c for

an example of how to do this.

Re: Gyroscope Code

Quote:

Originally Posted by Kevin Watson

...As always, if you find a bug in the code or a problem with the documentation, please let me know.

Well, I just discovered that I left one step out of the installation instructions found in gyro_readme.txt. Here are the revised instructions:

Nine things must be done before this software will work
correctly on your robot controller:

1) The gyro's rate output is wired to one of the analog inputs
of your robot controller and gyro.h/#define GYRO_CHANNEL is
updated with the analog channel your gyro is attached to.

2) A #include statement for the gyro.h header file must be
included at the beginning of each source file that calls the
functions in gyro.c. The statement should look like this:
#include "gyro.h".

3) Initialize_Gyro() must be called from user_routines.c/
User_Initialization().

4) Process_Gyro_Data() must be called when the ADC software
generates an update. An example of how to do this can be found
in user_routines_fast.c/Process_Data_From_Local_IO().

5) You must select the gyro you're using from a list in gyro.h
and if needed, remove the // in front of its #define.

6) The default angular unit is milliradians. If desired, this
can be changed to tenths of a degree by editing gyro.h

7) A gyro bias calculation must take place using the functions
Start_Gyro_Bias_Calc() & Stop_Gyro_Bias_Calc() described below.
This must be done several hundred milliseconds after the gyro
powers-up and is allowed to stabilize.

8) For optimal performance, you'll need to calibrate the gyro
scaling factor using the instructions above or those included
in gyro.h.

9) Follow the instructions found in adc_readme.txt for
installation instructions.

-Kevin

Re: Gyroscope Code

Thanks for the contribution to the First effort. I have a What if question.

What if First includes the EasyC environment for the 2006 season? Could your code be wrapped up and included into it? How about your serial port code?

Just curios as to you opinion if First goes down this path.

Re: Gyroscope Code

Quote:

Originally Posted by Gdeaver

What if First includes the EasyC environment for the 2006 season? Could your code be wrapped up and included into it? How about your serial port code?

Yes, the code can be ported fairly easily.

-Kevin

Re: Gyroscope Code

Is it possible to use a Murata gyro with the innovation controllers. If so, what changes would have to be made to the code so the controller can read the output from the gyro?

Re: Gyroscope Code

Quote:

Originally Posted by gmiller_1249

Is it possible to use a Murata gyro with the innovation controllers. If so, what changes would have to be made to the code so the controller can read the output from the gyro?

Yes, they can be used. The code changes are very simple to make. If you provide me with a part number, I can add it to the list of supported gyros.

-Kevin

Re: Gyroscope Code

Quote:

Originally Posted by Kevin Watson

Yes, they can be used. The code changes are very simple to make. If you provide me with a part number, I can add it to the list of supported gyros.

-Kevin

Murata ENV-05DB

Re: Gyroscope Code

Quote:

Originally Posted by gmiller_1249

Murata ENV-05DB

I've updated the gyro code to support this device. As I don't have one to test with, please let me know if you have any problems. The code can be found here: http://kevin.org/frc

-Kevin

Re: Gyroscope Code

I've updated the gyro code with version 0.3 of the analog to digital conversion code. As always, the code can be found here: http://kevin.org/frc

-Kevin

Re: Gyroscope Code

Well, I finally posted the ADC and Gyro code for the 2006 robot controller. Sorry about the delay, but I ran into a nasty bug that caused me to spend a few days in the fourth and fifth levels of programmer hell. The bug was in the design of the PIC18F8722 (yes, a bug in the sillicon) and I had to figure out what was going on. Anyway, the gyro code works really, really well with the gyro in the kit of parts. The accelerometers also work really well, but I need to do more testing before I unleash that code.

-Kevin

Re: Gyroscope Code

Quote:

Originally Posted by Kevin Watson

Thanks for all the hard work! With all the great sensors this year, how many interrupts can we use? Last year we use 4 pair of Hall sensors as quad counters, which worked well. The team is reluctant to move past success....so if I use those 4 pair, is there anything left on the 18F8722? And will using the camera code claim those interrupts as well?

Thans

Jon Mittelman
mentor
Team236

Re: Gyroscope Code

Kevin, you're like my own personal Jesus.

Re: Gyroscope Code

Quote:

Originally Posted by Kevin Watson

Well, I finally posted the ADC and Gyro code for the 2006 robot controller. ...

I just noticed that the gyro.h has DEFINEs to set the code to operate on a variety of gyro modules, but not the one that's in the 2006 KOP. According to US First's "2006_Sensor_Basic_Operation.pdf",

The actual Yaw Rate Gyro chip used on the 2006 YRG is the AD22304.

As far as I can tell, the only significant difference is the 80 degree/sec turning rate limit (vs. 150 dps on the ADXRS150).

Is there anything that needs to be adjusted in the code to handle this particular chip, or is it good enough just to leave the DEFINE the way it came?

Thanks again,
Dave

Re: Gyroscope Code

I've been having trouble getting the KOP gyro to work. I attached the two PWM cables to it and installed the gryo code. The output I get from the program seems to be in no way related to what is happening to the gyro. :confused: Also, why are two PWM cables used on the gyro, is one a temparture sensor(I read that it maybe somewhere)? I'm really a bit confused and any help would be greatly appreciated.

Re: Gyroscope Code

Quote:

Originally Posted by scitobor 617

is one a temparture sensor(I read that it maybe somewhere)?

I heard the head programmer from 68 talk about this...yes, it appears to have a temperature sensor onboard. He told me it measures in degrees Kelvin, but I don't know any of the details because he is the one that tinkered with the code and got it working. The best guess we have is that the gyro readings differ based on the temp........??? Kinda strange...umm.... :confused:

JBotAlan