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-   -   gyro and accelerometer problems (http://www.chiefdelphi.com/forums/showthread.php?t=63110)

paulcd2000 02-02-2008 13:01
gyro and accelerometer problems
 
Hey, we're using kevin's new 08 code (along with accelerometer we found on chiefdelphi), and when we disable the robot, it calibrates the gyro and the acceleromter. However, the gyro bias is -1, the rate is -21, and the angle never changes, even when we move the robot. Also, the accelerometer never yields any result but 0. Any ideas?

jgannon 02-02-2008 13:11
Re: gyro and accelerometer problems
 
As far as the gyro goes, are you sure that the wires are connected to the pins labeled T, and not the ones labeled R? This has been a really common mistake for years.

paulcd2000 02-02-2008 15:26
Re: gyro and accelerometer problems
 
no, i'm certain that that's not the issue. They use the weirdest naming system...

Jared Russell 02-02-2008 16:07
Re: gyro and accelerometer problems
 
Put in some printf's in the ADC interrupt handler to make sure the analog input is updating.

Also, did you do these?

Code:
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) The source code files gyro.c and gyro.h must be added to
your project.

3) 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".

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

5) 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(). If you
use the gyro during autonomous period, Process_Gyro_Data()
must also be called from User_Autonomous_Code().

6) You must select the gyro you're using from a list in gyro.h
and if needed, remove the // in front of its #define. If you're
using the gyro from the 2006 KOP, use the default ADXRS150
gyro.

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

8) 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.

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

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

Kevin Watson 02-02-2008 16:53
Re: gyro and accelerometer problems
 
Quote:
Originally Posted by Abwehr (Post 690817)
Put in some printf's in the ADC interrupt handler to make sure the analog input is updating.
Because printf() is a big chunk of code to execute in an ISR, it's probably better to just stuff an ASCII character directly into the serial port output queue, as described here.

-Kevin

paulcd2000 03-02-2008 12:09
Re: gyro and accelerometer problems
 
OK! so! i think i figured out the problem! it was probably the combination of
A: the gyro being plugged into the wrong port (curse you electrical people!), and B: the fact that i hadn't called Process_Gyro_Data() from Disabled_Spin()

paulcd2000 16-02-2008 15:17
Re: gyro and accelerometer problems
 
OK! so now it isn't working! I've called several print statements and writing chars. all the appropriate pieces get called, but the value of:
Code:
temp_gyro_rate = (int)Get_ADC_Result(GYRO_CHANNEL) - gyro_bias;
is always zero, even when we're turning the robot. i've ensured that the number of ADC channels is greater than the number of our channel.

the gyro rate is generally around 30 or -31, but jumps around between these, even though the robot is still during calibration, and these don't change when i'm rotating the robot

i'm completely stumped... could we need a new gyro?


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