[railerobotics]

Originally Posted by Kevin Watson

Here's my first-cut at code that will give an angle relative to the gravity vector, which points down. I'm working on a calibration routine for the bias,
but for now, just assume it's at the 2.5v mid-point. This code will work with the ADC code on my website. I imagine this code would work great for knowing what angle your ball launcher was at.

-Kevin

 
int Accel_Angle(void)
{
int x_axis;
int y_axis;
int angle;
 
x_axis = (int)Get_ADC_Result(X_AXIS_CHANNEL) - X_AXIS_BIAS;
 
y_axis = (int)Get_ADC_Result(Y_AXIS_CHANNEL) - Y_AXIS_BIAS;
 
angle = (int)(ANGULAR_CONVERSION * atan2((float)y_axis, (float)x_axis));
 
return(angle);
}
 
 

Here are the constants:

// Analog channel on the robot controller that's hooked-up to
// the x-axis accelerometer
#define X_AXIS_CHANNEL 1

 
// Analog channel on the robot controller that's hooked-up to
// the y-axis accelerometer
#define Y_AXIS_CHANNEL 2
 
// 800Hz sample rate & 16 samples averaged per update (see adc.h)

#define X_AXIS_BIAS 2048

#define Y_AXIS_BIAS 2048
 

// Pick the angular unit by removing the // from one of these two lines.
// #define MILLIRADIANS
// #define TENTHS_OF_A_DEGREE
#define DEGREES
 
 
#ifdef MILLIRADIANS
#define ANGULAR_CONVERSION 1000.0// milliradians per radian
#endif
 
#ifdef TENTHS_OF_A_DEGREE
#define ANGULAR_CONVERSION 573.0// tenths of a degree per radian
#endif
 
#ifdef DEGREES
#define ANGULAR_CONVERSION 57.3// degrees per radian
#endif
 
// function prototypes
int Accel_Angle(void);

In this code what is "atan2"? When I compile this code it gives me a prototyping error. I deleted the line with "atan2" and it compiled just fine. I can't seem to find "atan2" anywhere else in the code.