how to get pH in Java using Grove - PH Sensor Kit (E-201C-Blue) Raspberry pi Zero and GrovePi Zero Board

Question

I have GrovePi Zero（GrovePi0） from GrovePi Zero Base Kit and Grove - PH Sensor Kit (E-201C-Blue) I am using Java (I can use any version of JDK 8...17) on a Raspberry Pi Zerro 2. with GrovePi-pi4j with Pi4j version 1.4 (can use any version)

my class GrovePHSensor below represents the PH Sensor.

@GroveAnalogPin
public class GrovePHSensor extends GroveAnalogInputDevice<Double> {
   
public GrovePHSensor(GrovePi grovePi, int pin) throws IOException {
    super(grovePi.getAnalogIn(pin, 4));
}

@Override
public Double get(byte[] data) {
 /// WHAT TO DO HERE?
}
}

the problem is that there are tons of strange code out there that give different result and even if I think that I understand what it does I am not sure if it the right thing to do.

for example the this thread is very confusing https://forum.dexterindustries.com/t/grove-ph-sensor-kit-e-201c-blue-raspberry-pi-zero/7961/13

at the same time wiki page at Seeed https://wiki.seeedstudio.com/Grove-PH-Sensor-kit/ gives a sample code for Arduino with different formula

when I read the 4 byte[] i get something like [Pi4J IO read][0, 1, -106, -1] if i read more than 4 bytes than all the bytes at the end are -1

would be nice to have a clear implementation of the public Double get(byte[] data) {} function...

Answer 1

@GroveAnalogPin
public class GrovePHSensor extends GroveAnalogInputDevice<Double> {
     private static final Logger l = 
     LogManager.getLogger(GrovePHSensor.class.getName());
     /*** pH values range */
     public static final double PH_RANGE = 14.0;
    /*** 
      number of possible samples with 10 bit analog to digital converter 
     */
    public static final int A2D_RANGE = 1023;

public GrovePHSensor(GrovePi grovePi, int pin) throws IOException {
    super(grovePi.getAnalogIn(pin, 4));
}

@Override
public Double get(byte[] data) {
    // the extraction of the value is taken from the sample of the 
    // RotarySensor3Led 
    // https://github.com/DexterInd/GrovePi/blob/master/Software/Java8/GrovePi-spec/src/main/java/org/iot/raspberry/grovepi/devices/GroveRotarySensor.java
    // this is how its is done there

    int[] v = GroveUtil.unsign(data);
    double sensorValue = (v[1] * 256) + v[2];

    // the Analog to Digital is 10 bit -> 1023 intervals that cover the range of pH of 0 to 14
    // hence the pH value is the sensor value that is 0 to 1024
    // times the pH per interval of the A2D 14/1023
    double ph = sensorValue * (PH_RANGE / (double) A2D_RANGE);
    l.trace("sensorValue = {}  ph={}", sensorValue, ph);
    return ph;
    }
}