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Troubleshooting why Arduino logical operators doesn't compute

colporteur

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How would you write the expression to test sensors Departure (A or B) HIGH AND Arrival (A or B) HIGH?

The first else if statement shown below doesn't work. Departure A OR Departure B HIgh AND Arrival A OR Arrival B High. The OR doesn't work. Only when both Departure A AND B are HIGH the serial print. The same applies to the third else if statement both Departure A and B have to be low for the statement to function. What am I coding wrong for the OR?

      if ((digitalRead(s1DeparturePinA) == LOW || digitalRead(s1DeparturePinB) == LOW) &&
          (digitalRead(s1ArrivalPinA) == HIGH || digitalRead(s1ArrivalPinB) == HIGH))
        {
         Serial.println(F("Train on siding 1 status DEPARTURE")); 
         delay(1);
        }
      else if ((digitalRead(s1DeparturePinA) == HIGH || digitalRead(s1DeparturePinB) == HIGH)&&
               (digitalRead(s1ArrivalPinA) == HIGH || digitalRead(s1ArrivalPinB) == HIGH))
        {
          Serial.println(F("Train on siding 1 status IN TRANSIT"));
          delay(1);
        }
      else if ((digitalRead(s1DeparturePinA) == HIGH || digitalRead(s1DeparturePinB) == HIGH) &&
               (digitalRead(s1ArrivalPinA) == LOW || digitalRead(s1ArrivalPinB) == LOW))
        {
          Serial.println(F("Train on siding 1 status ARRIVAL"));
          delay(1);
          s1ArrivalDetect = LOW;
        }
      else if ((digitalRead(s1DeparturePinA) == LOW || digitalRead(s1DeparturePinB) == LOW) && 
               (digitalRead(s1ArrivalPinA) == LOW || digitalRead(s1ArrivalPinB) == LOW) &&
                s1ArrivalDetect == LOW)
        {
          Serial.println(F("Train on siding 1 status STOP"));
          delay(1);       
        trainOneOut = LOW; //train selection flip_flop L=train on siding 2
        s1ArrivalDetect = HIGH;
        digitalWrite(l1_TurnoutL, LOW);  //unset departure and arrival turnouts for train1
        digitalWrite(s1_Power, LOW);        //unset power on for train1
        digitalWrite(l1_TurnoutR, HIGH);  //set departure and arrival turnouts for train2
        digitalWrite(s2_Power, HIGH);        //set power on for train2
        }
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  • First assign each pin's status to a variable' then print that variable to the serial monitor.

    You can then see if it's related to your logic, or to a pin not being correctly read.

    Added bonus: if you then use those variables in your comparisons, yoy have less gpio function calls.

    Added bonus 2: consistent state throughout the evaluation. In your code, there is no guarantee that these pins have the same status during the logic's execution.

  • in reply to Jan Cumps

    Bare with me while I carve out an understanding.

    Before the first if statement, read the pins and assign the status to a variable. Then all the conditional statements are evaluated against those recorded states. The states are read each time through the loop.

  • in reply to colporteur

    Yes. And if you want to test the logic, I'd first manually assign TRUE or FALSE to the variables, instead of reading pins. And see if the code does what you expect.

    If it does, then assign the variables from pin state, and try again.

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