Gpiod

This library serves to control the digital pins of the embedded GPIO.

Requirements

In order to execute Gpiod methods at your embedded device, you will need to have the libgpiod-dev package installed in your board. You can do that by entering the following command at the device's terminal:

$ sudo apt-get install libgpiod-dev

Output

To activate and deactivate any external component the embedded board is to change the value of the GPIO pin that will activate it.

package com.totalcross.DocRpi;
import totalcross.ui.MainWindow;
import totalcross.ui.event.ControlEvent;
import totalcross.ui.event.PressListener;
import totalcross.ui.gfx.Color;
import totalcross.ui.Button;
import totalcross.io.device.gpiod.GpiodChip;
import totalcross.io.device.gpiod.GpiodLine;
import totalcross.sys.Settings;
public class DocRpi extends MainWindow {
// Integers to store state of each LED pin, 0 (LOW) and 1 (HIGH)
private int stt;
// Buttons to control
private Button btn;
public DocRpi(){
setUIStyle(Settings.MATERIAL_UI);
}
@Override
public void initUI(){
// Board Setup
GpiodChip gpioChip = GpiodChip.open(0); // GIPIO bus
GpiodLine pin = gpioChip.line(21); //
// Set LED pins as outputs and default value stt
pin.requestOutput("CONSUMER",stt);
// The TotalCross button:
btn = new Button("Pin"); // Button instantiation
// without text
btn.setBackColor(Color.RED); // Set background color (red)
btn.addPressListener(new PressListener(){ // Press event listener
@Override
public void controlPressed(ControlEvent controlEvent) {
stt = 1 - stt; // Invert pin state
pin.setValue(stt); // Set value (HIGH or LOW)
}
});
add(btn, CENTER, CENTER);
}
}

Input

In several embedded applications, it is necessary to receive digital signal from an external component such as sensors or even to activate another component indirectly.

package com.totalcross.DocRpi;
import totalcross.ui.MainWindow;
import totalcross.ui.event.ControlEvent;
import totalcross.ui.event.PressListener;
import totalcross.ui.gfx.Color;
import totalcross.ui.Button;
import totalcross.io.device.gpiod.GpiodChip;
import totalcross.io.device.gpiod.GpiodLine;
import totalcross.sys.Settings;
import totalcross.sys.Vm;
public class DocRpi extends MainWindow{
// Integers to store state of each LED pin, 0 (LOW) and 1 (HIGH)
private int stt;
// Buttons to control
private Button btn;
public DocRpi(){
setUIStyle(Settings.MATERIAL_UI);
}
@Override
public void initUI(){
// Board Setup
GpiodChip gpioChip = GpiodChip.open(0); // GIPIO bus
GpiodLine pin = gpioChip.line(21); //
// Set LED pins as outputs and default value stt
pin.requestOutput("CONSUMER", stt);
GpiodLine pinPushButton = gpioChip.line(22);
// Set Reset pin as input
pinPushButton.requestInput("CONSUMER");
new Thread(){
@Override
public void run(){
while(true){
if(pinPushButton.getValue() == 1){//check pin status
stt = 1 - stt; // Invert pin state
pin.setValue(stt); // Set value (HIGH or LOW)
}
Vm.sleep(200);
}
}
}.start();
}
}

Behind the Class

Methods

Type

Name

Description

Constructor

open(int chip)

Defines which GPIO bus will be used.

Construtor

line(int pin)

Defines which pin of GPIO bus will be used.

Void

requestOutput(String consumer, int defaultValue)

Names the pin, defines as output and the initial value.

Void

setValue(int value)

Changes pin value.

Void

requestInput(String consumer)

Names the pin and defines as input.

Int

getValue()

Returns pin status