Overflow with simple INT items

[mihalyn90]

Hello guys… here is a part of my code:

    line = qtra.readLine(sensors);
    unscaled_pos = line-2500;
    pos = unscaled_pos/hardscaler;
    Serial.print(pos);Serial.print("\t\t");
    derivative = 0;
    derivative = pos - last_pos;
    Serial.print(last_pos);Serial.print("\t\t");
    Serial.print(derivative);Serial.print("\t\t");
    last_pos = 0;
    last_pos = pos;
    diff = 0;
    diff = pos * P;
    Serial.print(diff);Serial.print("\t\t");
    diff = diff + derivative * D;
    Serial.print(diff);Serial.println();
    s_left = max_speed - diff;
    s_right = max_speed + diff;
    s_left = constrain(s_left, -255, 255);
    s_right = constrain(s_right, -255, 255);
    go_hard(s_left, s_right);

now no matter what…
I got pos = -5 and 5… values between, -5, -4, -3,… 3, 4, and 5
nos when I print out the “last_post”… I got values like -4958 etc…

now as I defined int last_post at the begining of the code, as a global variable… it’s working…

can somebody please explain why?

[taylorKaplan]

Hello.

Can you simplify this to the shortest program that demonstrates the issue (ideally, just a few lines of code) and post the full program along with a description of what you expect to happen and what actually happens?

If you have a workaround that fixes the problem (e.g. making something a global variable), could you post that full working program as well?

-Taylor

[mihalyn90]

the full code is here

#include <QTRSensors.h>
#include <SoftwareSerial.h>
#include <EEPROM.h>

int P, D, value_send, line, max_speed, s_left, s_right, minim, use_break;
int last_pos, diff, derivative, pos;
int menu = 0; 
int remote_stop = 0;
int mleft = 3;  //PWM control for motor outputs 1 and 2 is on digital pin 3
int mright = 11;  //PWM control for motor outputs 3 and 4 is on digital pin 11
byte remote;

QTRSensorsAnalog qtra((unsigned char[]) {0, 1, 2, 3, 4, 5}, 6);
unsigned int sensors[6]; 


void setup()
{
  TCCR2B = (TCCR2B & 0xF8) | 8;  //4 is default
  P = EEPROM.read(1);
  D = EEPROM.read(2);
  max_speed = EEPROM.read(3);
  value_send = EEPROM.read(4);
  use_break = EEPROM.read(5);
  minim = EEPROM.read(6);
  minim = -1*minim;
  pinMode(mleft, OUTPUT);
  pinMode(mright, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(2, OUTPUT);
  Serial.begin(9600);Serial.println();Serial.println();
  Serial.print("!Welcome to INSANITY PI Human machine interface! ");Serial.println();Serial.println();
  Serial.print("Booting INSANITY PI...");Serial.println();delay(250);
  Serial.print("Please be patient...");delay(250);Serial.println();
  Serial.print("Waiting Bluetooth connection stabilisation... ");delay(500);Serial.print("OK");Serial.println();
  Serial.print("Database loading... ");delay(250);Serial.print("OK");Serial.println();
  Serial.print("Accesing database... ");delay(125);Serial.print("OK");Serial.println();
  Serial.print("Reading stored values... ");delay(125);Serial.print("OK");Serial.println();
  Serial.print("Restoring PID values... ");delay(125);Serial.print("OK");Serial.println();
  Serial.print("Restoring speed values... ");delay(125);Serial.print("OK");Serial.println();delay(125);
  Serial.print("Stored values of PID are as following:");Serial.println();
  show_data();Serial.begin(9600);
  Serial.print("Insanity PI is now ONLINE");Serial.println();Serial.println();
  Serial.print("Send any key to continue... ");
  while(Serial.available()==0);
  Serial.println();Serial.println();
  Serial.end();
  
  while(menu!=10)
  {
  switch(menu)
  {
    case 0:
      Serial.begin(9600);
      Serial.print("Please select options: ");Serial.println();
      Serial.print(" 1. Configure PID");Serial.println();
      Serial.print(" 2. Race track");Serial.println();
      Serial.print(" 3. Calibrate Sensors");Serial.println();
      Serial.print(" 4. Set maximum speed");Serial.println();
      Serial.print(" 5. Show database values");Serial.println();
      Serial.print(" 6. USE/NOT USE breaking system");Serial.println();
      Serial.print(" 7. Enable/Disable DEBUG MODE");Serial.println();
      Serial.print(" 8. Set breaker speed");Serial.println();
      if(value_send == 1)
      {
        Serial.print(" 9. Race in DEBUG mode");Serial.println();
      }
      Serial.println();
      while(Serial.available()==0);
      menu = Serial.parseInt();
      Serial.end();
      break;
    case 1:
      pid_set();
      menu = 0;
      break;
    case 2:
      menu = 10;
      break;
    case 3:
      Serial.begin(9600);
      Serial.print("Calibration starts in... 3... ");delay(1000);
      Serial.print("2... ");delay(1000);
      Serial.print("1... ");delay(1000);Serial.println();
      Serial.print("Calibration started!");Serial.println();
      int i;
      for (int i = 0; i <= 80; i++)
      {
        if(i < 20 || i >= 60)
        {
          go(60,-60);
        }
        else
        {
          go(-60,60);
        }
        qtra.calibrate();
      }
      go(0,0);
      Serial.print("Calibration done succesfully!");Serial.println();
      Serial.print("Minimum treshold for each sensor is: ");Serial.println();
      for (i = 0; i < 6; i++)
      {
        Serial.print(qtra.calibratedMinimumOn[i]);Serial.print("\t");
      }
      Serial.println();
      Serial.print("Maximum treshold for each sensor is: ");Serial.println();
      for (i = 0; i < 6; i++)
      {
        Serial.print(qtra.calibratedMaximumOn[i]);Serial.print("\t");
      }
      Serial.println();Serial.println();
      Serial.end();
      menu = 0;
      break;
    case 4:
      Serial.begin(9600);
      Serial.print("Actual maximum speed is: ");Serial.print(max_speed);Serial.println();
      Serial.print("Please input maximum: ");
      while(Serial.available()==0);
      max_speed = Serial.parseInt();
      Serial.print(max_speed);
      EEPROM.write(3,max_speed);
      Serial.println();
      Serial.end();
      menu = 0;
      break;    
   case 5:
      show_data();
      Serial.println();Serial.println();
      Serial.end();   
      menu = 0;
      break;
   case 6:
      Serial.begin(9600);
      Serial.print("Currently ");
      if(use_break==0)
      {
        Serial.print("NOT ");
      }
      Serial.print("USING breaking system!");Serial.println();
      Serial.print("Please input 0(OFF)/1(ON): ");
      while(Serial.available()==0);
      use_break = Serial.parseInt();
      EEPROM.write(5, use_break);
      if(use_break == 1)
      {
       minim = EEPROM.read(6);
       minim = -minim;
       Serial.println();Serial.print("Breaking system has been enabled");Serial.println();
      }
      else
      {
       Serial.println();Serial.print("Breaking system has been disabled");Serial.println();
       minim = 0;
      }
      menu = 0;
      break;
   case 7:
     Serial.begin(9600);
     Serial.print("To recieve actual position and speed informations send 0(OFF)/1(ON): ");
     while(Serial.available()==0);
     value_send = Serial.parseInt();
     EEPROM.write(4,value_send);
     Serial.println();
     Serial.print("DEBUG MODE HAS BEEN ");
     if(value_send==0)
     {
       Serial.print("DISABLED");
     }
     else
     {
       Serial.print("ENABLED");
     }
     Serial.println();Serial.println();
     menu = 0;
     Serial.end();
     break;
   case 8:
     Serial.begin(9600);
     Serial.print("Breaking speed is: ");Serial.print(minim);Serial.println();
     Serial.print("Please input breaking speed: ");
     while(Serial.available()==0);
     minim = Serial.parseInt();
     EEPROM.write(6,minim);
     minim = -1*minim;
     Serial.print(minim);
     Serial.println();
     Serial.end();
     menu = 0;
     break; 
   case 9:
     Serial.begin(9600);
     value_send = 1;
     menu = 10;
     break;
   }
  }
    
  digitalWrite(12, LOW);
  digitalWrite(13, HIGH);
  analogWrite(mleft, max_speed);
  analogWrite(mright, max_speed);


}

void loop()
{
  while(remote_stop==1)
  {
    Serial.print("STOPPED");Serial.println();
    Serial.print("Please reset INSANITY PI!");Serial.println();Serial.println();
    go(-max_speed, -max_speed);
    delay(5);
    go(0, 0);
    while(1);
  }
  line = qtra.readLine(sensors);
  pos = line-2500;
  derivative = pos - last_pos;
  last_pos = pos;
  diff = pos/P + derivative*D/2;
  if(diff<0)
  {
    s_left = max_speed;
    s_right = max_speed + diff;
  }
  else
  {
    s_left = max_speed - diff;
    s_right = max_speed;
  }
  s_left = constrain(s_left, minim, max_speed);
  s_right = constrain(s_right, minim, max_speed);
  go(s_left, s_right);
  if(value_send==1)
  {
    Serial.print(pos);Serial.print("\t\t");Serial.print(s_left);Serial.print("\t\t");Serial.print(s_right);Serial.println();
  }
}

void pid_set()
{
  Serial.end();Serial.begin(9600);
  Serial.println();
  Serial.print("Previsious data for PID were:");Serial.println();
  Serial.print("kP: ");Serial.print(P);Serial.print(" kD: ");Serial.print(D);Serial.println();
  Serial.print("Setting up for SPEED track... ");Serial.println();
  Serial.print(" kP = ");
  while(Serial.available()==0);
  P = Serial.parseInt();
  Serial.print(P);
  EEPROM.write(1,P);
  Serial.end();
  Serial.begin(9600);
  Serial.print(" kD = ");
  while(Serial.available()==0);
  D = Serial.parseInt();
  Serial.print(D);
  EEPROM.write(2, D);  
  Serial.println();Serial.println();
  Serial.end();
  menu = 0;
}


void go(int speedLeft, int speedRight) 
{
  if (speedLeft > 0) 
  {
    digitalWrite(12, LOW);
    analogWrite(mleft, speedLeft);
  }
  else 
  {
    digitalWrite(12, HIGH);
    analogWrite(mleft, -speedLeft);
  }


  if (speedRight > 0)
  {
    digitalWrite(13, HIGH);
    analogWrite(mright, speedRight);
  }
  else 
  {
    digitalWrite(13, LOW);
    analogWrite(mright, -speedRight);
  }
}




void show_data()
{
  Serial.begin(9600);
  Serial.print("PID: ");Serial.print("\t\t");Serial.print("kP:");Serial.print(P);Serial.print("\t\t");Serial.print("kD:");Serial.print(D);Serial.print("\t\t");Serial.print("speed:");Serial.print(max_speed);Serial.println();
  if(use_break==0)
  {
    Serial.print("NOT ");
  }
  Serial.print("USING breaking system");
  if(use_break==1)
  {
    Serial.print(" with breaker speed of ");Serial.print(minim);Serial.println();
  }
  Serial.println();
  Serial.print("DEBUG mode is ");
  if(value_send==0)
    {
      Serial.print("DISABLED");
    }
    else
    {
      Serial.print("ENABLED");
    }
    Serial.println();Serial.println();
    Serial.end();
}


void serialEvent()
{
  remote = Serial.read();
  if(remote == 's');
  remote_stop=1;
}

and right now is working… got 4th place in a competition…

- YouTube

[taylorKaplan]

I’m glad you got it working. Congratulations on your 4th place finish!

-Taylor