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I/O reading Problem

e14 Contributor
e14 Contributor

I created a small program on the Arduino coding platform and it compiles fine, but when it is tested on my breadboard it does not work. I think that I messed up somewhere in the coding since i'm a beginner, anyway here is the code: 

int lightA = 0;

int lightB = 0;

 

 

void setup(){

pinMode(13, INPUT);

  pinMode(12, INPUT);

   pinMode(8, OUTPUT);

    pinMode(7, OUTPUT);

}

void loop(){

  lightA = digitalRead(13);

  lightB = digitalRead(12);

  if (lightA == HIGH){

   digitalWrite(8, HIGH);

    digitalWrite(7, LOW);

  }

  if (lightB == HIGH){

   digitalWrite(8, LOW);

    digitalWrite(7, HIGH);

  }

  else{

   digitalWrite(8, LOW);

    digitalWrite(7, LOW);

  }

 

 

}

 

If you can find what i'm doing wrong please post!

Parents
  • 0

    do you have pull up resistors on the inputs ?

     

    are the outputs doing anything ?

     

    also

     

    you need the additional ifs to have an else in front of them otherwise you will have the situation where only if A and B are low will both outputs be low if b input is high then it will always override input a

     

    so what you should be getting is this:-

    A=HIGH and B=HIGH = output 8=  LOW, 7 = HIGH

    A=LOW and B=HIGH = output 8=  LOW, 7 = HIGH

    A=HIGH and B=LOW = output 8 = HIGH, 7 = LOW

    A=LOW and B=LOW = output 8 = LOW, 7 = LOW

     

    if you wanted this

    A=HIGH and B=HIGH = output 8=  HIGH, 7 = LOW

    A=LOW and B=HIGH = output 8=  LOW, 7 = HIGH

    A=HIGH and B=LOW = output 8 = HIGH, 7 = LOW

    A=LOW and B=LOW = output 8 = LOW, 7 = LOW

     

    if (lightA == HIGH){
   digitalWrite(8, HIGH);
    digitalWrite(7, LOW);
  }
 else if (lightB == HIGH){
   digitalWrite(8, LOW);
    digitalWrite(7, HIGH);
  }
  else{
   digitalWrite(8, LOW);
    digitalWrite(7, LOW);
  }

Reply
  • 0

    do you have pull up resistors on the inputs ?

     

    are the outputs doing anything ?

     

    also

     

    you need the additional ifs to have an else in front of them otherwise you will have the situation where only if A and B are low will both outputs be low if b input is high then it will always override input a

     

    so what you should be getting is this:-

    A=HIGH and B=HIGH = output 8=  LOW, 7 = HIGH

    A=LOW and B=HIGH = output 8=  LOW, 7 = HIGH

    A=HIGH and B=LOW = output 8 = HIGH, 7 = LOW

    A=LOW and B=LOW = output 8 = LOW, 7 = LOW

     

    if you wanted this

    A=HIGH and B=HIGH = output 8=  HIGH, 7 = LOW

    A=LOW and B=HIGH = output 8=  LOW, 7 = HIGH

    A=HIGH and B=LOW = output 8 = HIGH, 7 = LOW

    A=LOW and B=LOW = output 8 = LOW, 7 = LOW

     

    if (lightA == HIGH){
   digitalWrite(8, HIGH);
    digitalWrite(7, LOW);
  }
 else if (lightB == HIGH){
   digitalWrite(8, LOW);
    digitalWrite(7, HIGH);
  }
  else{
   digitalWrite(8, LOW);
    digitalWrite(7, LOW);
  }

Children
  • e14 Contributor
    0 e14 Contributor in reply to Robert Peter Oakes

    Well when I start the program on the Arduino both of the lights turn on and I do have resistors on the outputs.

  • 0 in reply to e14 Contributor

    what about the inputs ?, im assuming some kind of pull up on the inputs and a switch to short to ground ?

     

    also you are not setting the outputs to any state after initializing them to output

    do this

     

    void setup(){

         pinMode(13, INPUT);

         pinMode(12, INPUT);

         pinMode(8, OUTPUT);

         pinMode(7, OUTPUT);

          digitalWrite(8, LOW); 

          digitalWrite(7, LOW);

    }

  • e14 Contributor
    0 e14 Contributor in reply to Robert Peter Oakes

    I had been using a regular 220Ω resistor for the inputs and I didn't have a switch to ground so ill add that and ill have to revise my script. Thanks! 

  • 0 in reply to Robert Peter Oakes

    Pin 13 has the LED across it, so not a good choice for an input.

    it will tend by low all the time.

     

    By default the Outputs are low when you set them as an output, however its a good practice to set the state JUST so you know.

     

    My guess it needs resistors between the pin and ground.

    The switch is likely to go from +5v to the pin

     

      else{

       digitalWrite(8, LOW);

        digitalWrite(7, LOW);

     

    otherwise you'd need to hold the switch all the time.

     

    You could try this which compiles and should work.

     

    int LightA = 12;  // set the outputs
int LightB = 13;  // set the outputs
int ButtonA = 7;  // set the input ** Add a resistor from the pin to ground, switch goes from 5v to the pin
int ButtonB = 8;  // set the input ** Add a resistor from the pin to ground, switch goes from 5v to the pin

void setup()
{
 pinMode(LightA, OUTPUT);
 pinMode(LightB, OUTPUT);
 pinMode(ButtonA, INPUT);
 pinMode(ButtonB, INPUT);
}

void loop()
{
  digitalRead(ButtonA);
  digitalRead(ButtonB);
  digitalWrite(LightA, ButtonA);
  digitalWrite(LightB, ButtonB);
}

}

     

     

    This link here gives good information about what is happening with the pins.

    http://www.baldengineer.com/tutorials/arduino-pull-ups/

     

    mark