I think this should do it. Whats in bold I added.
/*
This program is used to create an Inclinometer using a
Raspberry Pi and an IMU
https://ozzmaker.com/2014/12/12/inclinometer-using-raspberry-pi-imu/
Copyright (C) 2014 Mark Williams
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place – Suite 330, Boston,
MA 02111-1307, USA
*/
#include “SDL.h”
#include “SDL/SDL_image.h”
#include <unistd.h>
#include <math.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
#include “sensor.c”
#define DT 0.2 //
#define AA 0.97 // complementary filter constant
#define A_GAIN 0.0573 // [deg/LSB]
#define G_GAIN 0.070 // [deg/s/LSB]
#define RAD_TO_DEG 57.29578
#define M_PI 3.14159265358979323846
//Used by Kalman Filters
float Q_angle = 0.01;
float Q_gyro = 0.0003;
float R_angle = 0.01;
float x_bias = 0;
float y_bias = 0;
float XP_00 = 0, XP_01 = 0, XP_10 = 0, XP_11 = 0;
float YP_00 = 0, YP_01 = 0, YP_10 = 0, YP_11 = 0;
float KFangleX = 0.0;
float KFangleY = 0.0;
float kalmanFilterX(float accAngle, float gyroRate);
float kalmanFilterY(float accAngle, float gyroRate);
int graphics(float carRoll, float carPitch);
int startSDL();
SDL_Surface* screen = NULL;
SDL_Surface* inclinometerJeepFront = NULL;
SDL_Surface* inclinometerJeepSide = NULL;
SDL_Surface* inclinometerOverlay = NULL;
SDL_Surface* compatibleInclinometerJeepFront = NULL;
SDL_Surface* compatibleInclinometerJeepSide = NULL;
SDL_Surface* compatibleInclinometerOverlay = NULL;
SDL_Surface* rotationInclinometerJeepFront = NULL;
SDL_Surface* rotationInclinometerJeepSide = NULL;
SDL_Rect inclinometerJeepOverlayPosition;
SDL_Rect inclinometerJeepFrontPosition;
SDL_Rect inclinometerJeepSidePosition;
SDL_VideoInfo* videoInfo;
void INThandler(int sig)
{
SDL_FreeSurface(screen);
SDL_Quit();
signal(sig, SIG_IGN);
exit(0);
}
int mymillis()
{
struct timeval tv;
gettimeofday(&tv, NULL);
return (tv.tv_sec) * 1000 + (tv.tv_usec)/1000;
}
int timeval_subtract(struct timeval *result, struct timeval *t2, struct timeval *t1)
{
long int diff = (t2->tv_usec + 1000000 * t2->tv_sec) – (t1->tv_usec + 1000000 * t1->tv_sec);
result->tv_sec = diff / 1000000;
result->tv_usec = diff % 1000000;
return (diff<0);
}
int main(int argc, char *argv[])
{
float rate_gyr_y = 0.0; // [deg/s]
float rate_gyr_x = 0.0; // [deg/s]
float rate_gyr_z = 0.0; // [deg/s]
int acc_raw[3];
int mag_raw[3];
int gyr_raw[3];
float gyroXangle = 0.0;
float gyroYangle = 0.0;
float gyroZangle = 0.0;
float AccYangle = 0.0;
float AccXangle = 0.0;
float CFangleX = 0.0;
float CFangleY = 0.0;
int startInt = mymillis();
struct timeval tvBegin, tvEnd,tvDiff;
signed int acc_y = 0;
signed int acc_x = 0;
signed int acc_z = 0;
signed int gyr_x = 0;
signed int gyr_y = 0;
signed int gyr_z = 0;
signal(SIGINT, INThandler);
enableIMU();
gettimeofday(&tvBegin, NULL);
if(argc <=1)
startSDL();
else if (strcmp(argv[1],”nosdl”)!= 0)
startSDL();
while(1)
{
startInt = mymillis();
//read ACC and GYR data
readACC(acc_raw);
readGYR(gyr_raw);
//Convert Gyro raw to degrees per second
rate_gyr_x = (float) gyr_raw[0] * G_GAIN;
rate_gyr_y = (float) gyr_raw[1] * G_GAIN;
rate_gyr_z = (float) gyr_raw[2] * G_GAIN;
//Calculate the angles from the gyro
gyroXangle+=rate_gyr_x*DT;
gyroYangle+=rate_gyr_y*DT;
gyroZangle+=rate_gyr_z*DT;
//Convert Accelerometer values to degrees
AccXangle = (float) (atan2(acc_raw[1],acc_raw[2])+M_PI)*RAD_TO_DEG;
AccYangle = (float) (atan2(acc_raw[2],acc_raw[0])+M_PI)*RAD_TO_DEG;
//Change the rotation value of the accelerometer to -/+ 180 and move the Y axis ‘0’ point to up.
//Two different pieces of code are used depending on how your IMU is mounted.
//If IMU is upside down
/*
if (AccXangle >180)
AccXangle -= (float)360.0;
AccYangle-=90;
if (AccYangle >180)
AccYangle -= (float)360.0;
*/
//If IMU is up the correct way, use these lines
AccXangle -= (float)180.0;
if (AccYangle > 90)
AccYangle -= (float)270;
else
AccYangle += (float)90;
//Kalman Filter
float kalmanX = kalmanFilterX(AccXangle, rate_gyr_x);
float kalmanY = kalmanFilterY(AccYangle, rate_gyr_y);
printf (“33[22;31mkalmanX %7.3f 33[22;36mkalmanY %7.3f\t\e[m”,kalmanX,kalmanY);
//Complementary filter used to combine the accelerometer and gyro values.
CFangleX=AA*(CFangleX+rate_gyr_x*DT) +(1 – AA) * AccXangle;
CFangleY=AA*(CFangleY+rate_gyr_y*DT) +(1 – AA) * AccYangle;
printf (” GyroX %7.3f \t AccXangle \e[m %7.3f \t 33[22;31mCFangleX %7.3f33[0m\t GyroY %7.3f \t AccYangle %7.3f \t 33[22;36mCFangleY %7.3f\t33[0m\n”,gyroXangle,AccXangle,CFangleX,gyroYangle,AccYangle,CFangleY);
if(argc <=1)
graphics(kalmanX,kalmanY);
else if (strcmp(argv[1],”nosdl”)!= 0)
graphics(kalmanX,kalmanY);
//Each loop should be at least 20ms.
while(mymillis() – startInt < (DT*1000))
{
usleep(100);
}
printf(“Loop Time %d\t”, mymillis()- startInt);
}
}
int startSDL()
{
//fb1 = small TFT. fb0 = HDMI/RCA output
putenv(“SDL_FBDEV=/dev/fb0”);
//Initialize SDL and disable mouse
SDL_Init(SDL_INIT_VIDEO);
SDL_ShowCursor(SDL_DISABLE);
//Get information about the current video device. E.g. resolution and bits per pixal
videoInfo = SDL_GetVideoInfo ();
//Setup a Video mode.
screen = SDL_SetVideoMode(videoInfo->current_w, videoInfo->current_h, videoInfo->vfmt->BitsPerPixel, SDL_SWSURFACE );
if ( screen == NULL ) {
fprintf(stderr, “Unable to setvideo: %s\n”, SDL_GetError());
exit(1);
}
//Load image.
inclinometerJeepFront = IMG_Load(“inclinometerJeepFront.png”);
if (inclinometerJeepFront == NULL){
printf(“error loading JeepFront image\n”);
SDL_Quit();
exit(1);
}
//Convert the image to a format we can use.
compatibleInclinometerJeepFront = SDL_DisplayFormatAlpha(inclinometerJeepFront);
//Load image.
inclinometerJeepSide = IMG_Load(“inclinometerJeepSide.png”);
if (inclinometerJeepSide == NULL){
printf(“error loading JeepSide image\n”);
SDL_Quit();
exit(1);
}
//Convert the image to a format we can use.
compatibleInclinometerJeepSide = SDL_DisplayFormatAlpha(inclinometerJeepSide);
//Load image.
inclinometerOverlay = IMG_Load(“inclinometerOverlay.png”);
if (inclinometerOverlay == NULL){
printf(“error loading Overlay image\n”);
SDL_Quit();
exit(1);
}
//Convert the image to a format we can use.
compatibleInclinometerOverlay = SDL_DisplayFormatAlpha(inclinometerOverlay);
//Position the overlay in the middle of the screen. screen heigth minus the height of the overlay image.
inclinometerJeepOverlayPosition.y = (videoInfo->current_h/2)-(compatibleInclinometerOverlay->h/2);
}
int graphics(float carRoll, float carPitch)
{
//Set all pixals to black to clear the last image.
SDL_FillRect(screen,NULL,0x000000);
//Position of both jeep images.
inclinometerJeepFrontPosition.x = 30;
inclinometerJeepFrontPosition.y = (videoInfo->current_h/2)-(compatibleInclinometerJeepFront->h/2);
inclinometerJeepSidePosition.x = 262;
inclinometerJeepSidePosition.y = (videoInfo->current_h/2)-(compatibleInclinometerJeepFront->h/2);
//Rotate the images based on pitch and roll.
rotationInclinometerJeepSide = rotozoomSurface(compatibleInclinometerJeepSide, carPitch, 1.0, 0.0);
rotationInclinometerJeepFront = rotozoomSurface(compatibleInclinometerJeepFront, carRoll, 1.0, 0.0);
//Recenter pivot point.
inclinometerJeepFrontPosition.x -= rotationInclinometerJeepFront->w/2-compatibleInclinometerJeepFront->w/2;
inclinometerJeepFrontPosition.y -= rotationInclinometerJeepFront->h/2-compatibleInclinometerJeepFront->h/2;
inclinometerJeepSidePosition.x -= rotationInclinometerJeepSide->w/2-compatibleInclinometerJeepSide->w/2;
inclinometerJeepSidePosition.y -= rotationInclinometerJeepSide->h/2-compatibleInclinometerJeepSide->h/2;
//Blit the three iamges to the surface.
SDL_BlitSurface( compatibleInclinometerOverlay, NULL, screen, &inclinometerJeepOverlayPosition);
SDL_BlitSurface( rotationInclinometerJeepFront, NULL, screen, &inclinometerJeepFrontPosition);
SDL_BlitSurface( rotationInclinometerJeepSide, NULL, screen, &inclinometerJeepSidePosition);
//Send the surface to the display.
SDL_Flip(screen);
//Free surfaces.
SDL_FreeSurface(screen);
SDL_FreeSurface(rotationInclinometerJeepFront);
SDL_FreeSurface(rotationInclinometerJeepSide);
return 0;
}
float kalmanFilterX(float accAngle, float gyroRate)
{
float y, S;
float K_0, K_1;
KFangleX += DT * (gyroRate – x_bias);
XP_00 += – DT * (XP_10 + XP_01) + Q_angle * DT;
XP_01 += – DT * XP_11;
XP_10 += – DT * XP_11;
XP_11 += + Q_gyro * DT;
y = accAngle – KFangleX;
S = XP_00 + R_angle;
K_0 = XP_00 / S;
K_1 = XP_10 / S;
KFangleX += K_0 * y;
x_bias += K_1 * y;
XP_00 -= K_0 * XP_00;
XP_01 -= K_0 * XP_01;
XP_10 -= K_1 * XP_00;
XP_11 -= K_1 * XP_01;
return KFangleX;
}
float kalmanFilterY(float accAngle, float gyroRate)
{
float y, S;
float K_0, K_1;
KFangleY += DT * (gyroRate – y_bias);
YP_00 += – DT * (YP_10 + YP_01) + Q_angle * DT;
YP_01 += – DT * YP_11;
YP_10 += – DT * YP_11;
YP_11 += + Q_gyro * DT;
y = accAngle – KFangleY;
S = YP_00 + R_angle;
K_0 = YP_00 / S;
K_1 = YP_10 / S;
KFangleY += K_0 * y;
y_bias += K_1 * y;
YP_00 -= K_0 * YP_00;
YP_01 -= K_0 * YP_01;
YP_10 -= K_1 * YP_00;
YP_11 -= K_1 * YP_01;
return KFangleY;
}
