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From Felipe Gutierrez <felipe.o.gutier...@gmail.com>
Subject How to filter on Apache Edgent and also show the values which were filtered?
Date Wed, 21 Nov 2018 14:57:42 GMT
Hi,

This question is about an application that I am using Apache Edgent, not
really a development effort into Apache Edgent. But as there is no user@list
I am sensding here.

I am using Apache Edgent  (Java framework) to poll values from an HCSR04
ultrasonic sensor on a Raspberry Pi every 3 seconds. I use a filter to not
get values from 50cm to 80cm (
https://github.com/felipegutierrez/explore-rpi/blob/master/src/main/java/org/sense/edgent/app/UltrasonicEdgentApp.java
).

UltrasonicStream sensor = new UltrasonicStream();
DirectProvider dp = new DirectProvider();
Topology topology = dp.newTopology();
TStream<Double> tempReadings = topology.poll(sensor, 3, TimeUnit.SECONDS);
TStream<Double> filteredReadings = tempReadings.filter(reading -> reading <
50 || reading > 80);
System.out.println("filter added: tempReadings.filter(reading -> reading <
50 || reading > 80);");
filteredReadings.print();
dp.submit(topology);

I want to show some message when the values are filtered. When the values
do not match with my filter I can poll them, but when they match I am not
returning, that is ok. However, I want just to show that a value was
filtered using Apache Edgent libraries. I know that I can do something on
the `public double get()` method, but I wonder if I could do this trick
with some method of the Apache Edgent (
https://github.com/felipegutierrez/explore-rpi/blob/master/src/main/java/org/sense/sensor/UltrasonicStream.java
).

public class UltrasonicStream implements Supplier<Double> {

private static final long serialVersionUID = -6511218542753341056L;

private static GpioPinDigitalOutput sensorTriggerPin;
private static GpioPinDigitalInput sensorEchoPin;
private static final GpioController gpio = GpioFactory.getInstance();
private double currentDistance = -1.0;

/**
* The HCSR04 Ultrasonic sensor is connected on the physical pin 16 and 18
which
* correspond to the GPIO 04 and 05 of the WiringPi library.
*/
public UltrasonicStream() {
// Trigger pin as OUTPUT
sensorTriggerPin = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_04);
// Echo pin as INPUT
sensorEchoPin = gpio.provisionDigitalInputPin(RaspiPin.GPIO_05,
PinPullResistance.PULL_DOWN);
}

/**
* This is the override method of the Supplier interface from Apache Edgent
*/
@Override
public Double get() {
try {
System.out.print("Distance in centimeters: ");
currentDistance = getDistance();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return currentDistance;
}

/**
* Retrieve the distance measured by the HCSR04 Ultrasonic sensor connected
on a
* Raspberry Pi 3+B
*
* @return the distance in centimeters
* @throws InterruptedException
*/
public double getDistance() throws InterruptedException {

double distanceCM = -1;
try {
// Thread.sleep(2000);
sensorTriggerPin.high(); // Make trigger pin HIGH
Thread.sleep((long) 0.01);// Delay for 10 microseconds
sensorTriggerPin.low(); // Make trigger pin LOW

// Wait until the ECHO pin gets HIGH
while (sensorEchoPin.isLow()) {

}
// Store the current time to calculate ECHO pin HIGH time.
long startTime = System.nanoTime();
// Wait until the ECHO pin gets LOW
while (sensorEchoPin.isHigh()) {

}
// Store the echo pin HIGH end time to calculate ECHO pin HIGH time.
long endTime = System.nanoTime();

distanceCM = ((((endTime - startTime) / 1e3) / 2) / 29.1);
// Printing out the distance in centimeters
// System.out.println("Distance: " + distanceCM + " centimeters");

return distanceCM;
} catch (InterruptedException e) {
e.printStackTrace();
}
return distanceCM;
}
}

Thanks,
Felipe

*--*
*-- Felipe Gutierrez*

*-- skype: felipe.o.gutierrez*
*--* *https://felipeogutierrez.blogspot.com
<https://felipeogutierrez.blogspot.com>*

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