Analog to Arduino digital value conversion

Question

Hello, I am developing a line follower robot the sensor that performs the reading is analog (0 - 255) QTR Polulu, but the design requires that digital values (0 - 1) be used in the comparisons of values such as:

if(digitalRead(sensor1) > digitalRead(sensor2)){ ... } 

So how can I convert an analog value to digital? It would be possible to do this with PWM as:

#define pin = 13; //pino PWM
void setup() { ... }
int leitura = digitalRead(pin); //0 - 1

Thank you very much from now on!

Answer 1

Trying to clarify some concepts about the first if: When talking about digital, one has in mind only the values 0 and 1 logical, ie: booleans false and true. Therefore, a digital reading has a value "higher" than another only means that one is on and the other is off. Using a mathematical comparison operator in this case does not "close" for the purpose: after all, how to compare if a true is greater than a false ? (Of course, the compiler finds a way to solve this, but for those who read the code it can get a little strange.

In the case of analogue readings, the function to be used is analogRead(PINO). This function returns a value from 0 to 1023, since the Arduino digital analog converter works with 10 bits (so remember to use a int and not a char). Now, how to convert the values 0 to 1023 into "digital"? You can do various analog readings and send by serial to follow on Serial Monitor. With this you will know what is the cutting distance/limit of your sensor. For example: in the distance you want to measure, the reading returns around 700 (sometimes 695, 697, 702, etc.). Then one can consider a logical value 1 (the presence of an object) the readings below 710.

#define PINO 3
int valor = 0;
bool objetoPresente = false;
void setup()
{
    Serial.begin(9600);
}

void loop()
{
    valor = analogRead(PINO);
    Serial.println(valor); // manda o valor para a serial

    if (valor <= 710) {
        // objeto na frente do sensor a uma distância limite
        objetoPresente = true;
    }
    else {
        objetoPresente = false;
    }
}

Reference: https://www.arduino.cc/en/Reference/AnalogRead

PS: I’ve never worked with this QTR Pololu sensor, but googlando it, it has a specific bibliotea: https://www.pololu.com/docs/0J19/all and some videos on Youtube.

I hope I’ve helped!