Arduino doesn't recognize long integer datatype

[Foad S. Farimani]

I have a simple model with some LEDs and potentiometers (in the attachment) and the code below:

int potPin1 = A0;  
int potPin2 = A1;

int ledPin1 = 2;   
int ledPin2 = 3;   
int ledPin3 = 4;   

long val1 = 0;   
long val2 = 0; 
int Tmax = 1000;   

void setup() {
  pinMode(ledPin1, OUTPUT);  
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  val1 = analogRead(potPin1) * Tmax / 1024;   
  val2 = analogRead(potPin2) * val1 / 1024; 
  Serial.print(val1);
  Serial.print(", ");
  Serial.println(val2);
  digitalWrite(ledPin1, HIGH);  
  delay(val2);                  
  digitalWrite(ledPin1, LOW);   
  delay(val1 - val2);                  
}

but I get negative values :

It seems like a bug to me.

[Foad S. Farimani]

For the moment I used a float variable as a workaround:

int potPin1 = A0;  
int potPin2 = A1;

int ledPin1 = 2;   
int ledPin2 = 3;   
int ledPin3 = 4;   

int val1 = 0; 
int val1_ = 0;  
int val2 = 0; 
int val2_ = 0;
float tmpf = 0.0;
float Tmax = 1000;
unsigned long T = millis();
int dt = 0;   

void setup() {
  pinMode(ledPin1, OUTPUT);  
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  tmpf = analogRead(potPin1) * (Tmax / 1024.0);   
  val1 = (int) tmpf;
  tmpf = analogRead(potPin2) * (tmpf / 1024.0); 
  val2 = (int) tmpf;

  if (val1 != val1_ || val2 != val2_) {
    val1_ = val1;
    val2_ = val2;
    Serial.print(val1);
    Serial.print(", ");
    Serial.println(val2);
  }

  dt = millis() - T;
  if ((dt == 0 || val1 <= dt)) {
    T = millis();
    digitalWrite(ledPin1, HIGH);
  }    
  if (val2 <= dt) {
    digitalWrite(ledPin1, LOW);
  }                
}

[Santiago]

Hi.
Think this is nothing about simulide, this is about using variable types in C/C++;

In the first case you are using integer numbers calculations then store into a long, integers overflow, so you get negative numbers. Cast to long and it will work as espected.

[Foad S. Farimani]

aha! so basically the output of the analogRead is int anyways and the temporary memory used for arithmetics is the same as the operator pairs. if I do ((long) analogRead(...)) it should be solved. Will try and come back.

[Foad S. Farimani]

this worked great. Thanks a lot.
As a side feature request, the rotating wheel for potentiometer is a bit difficult to control. it would be great if one could change it to a slider and/or put the values manually (e.g. in the properties section).

[Santiago]

You can put the value in potentiometer properties (the last property: "Value Ohm").

And manually there is a trick to controll it with accuracy:
Click on the pot wheel and hold it, then move mouse pointer outside of the pot as far as you want, the moving mouse pointer in a circle around the pot. The further you go from pot the more accurate you can change the value.