A problem ---"cannot convert from void to boolean"

zheng

                    `import org.firmata.*;
                    import cc.arduino.*;
                    import processing.serial.*;
                    Arduino arduino;

                    int s1 = 7;//(r) //sensor1
                    int s2 = 8;//(y) //sensor2
                    int s3 = 9;//(b) //sensor3
                    int s4 = 10;//(g)//sensor4
                    int s5 = 11;//(b)//sensor5


                    void setup() {
                     size(500, 500);
                     background(255);
                     println(Arduino.list());

                     arduino = new Arduino(this, Arduino.list()[4], 57600); 
                     arduino.pinMode(s1, Arduino.INPUT);
                     arduino.pinMode(s2, Arduino.INPUT);
                     arduino.pinMode(s3, Arduino.INPUT);
                     arduino.pinMode(s4, Arduino.INPUT);
                     arduino.pinMode(s5, Arduino.INPUT);
                    }
                    void draw() {
                     if (arduino.digitalWrite(s1, Arduino.LOW)) {
                       ellipse(50, 50, 50, 50);
                     }
                    }
                    `

When the sensor gets information, a circle will appear. But now it cannot work! WHY?

colouredmirrorball

Please format your code using the C button (ctrl+o). Nobody is going to read your code like that.

Your error appears for example when you use a method that doesn't return anything in a place where the compiler expects a boolean, like in the condition of an if statement.

AverageJoe

arduino.digitalWrite(s1, Arduino.LOW) returns void because it writes, not reads.

You want arduino.digitalRead(s1, Arduino.LOW)

It's right on the front page for the firmata library. Scroll down a bit for available commands
http://playground.arduino.cc/Interfacing/Processing

zheng

@AverageJoe Thank you so much for your help. I achieved it.

zheng

@colouredmirrorballcolouredmirrorball Thank you so much