Package jdk.dio.gpio

Interfaces and classes for reading and writing from/to GPIO (General Purpose Input Output) pins and ports of the device.

See: Description

Interface Summary

Interface	Description
GPIOPin	The GPIOPin interface provides methods for controlling a GPIO pin.
GPIOPort	The GPIOPort interface provides methods for controlling a GPIO port.
PinListener	The PinListener interface defines methods for getting notified of GPIO pin value changes.
PortListener	The PortListener interface defines methods for getting notified of GPIO port value changes.

Class Summary

Class	Description
GPIOPinConfig	The GPIOPinConfig class encapsulates the hardware addressing information, and static and dynamic configuration parameters of a GPIO pin.
GPIOPinPermission	The GPIOPinPermission class defines permissions for GPIO pin access.
GPIOPortConfig	The GPIOPortConfig class encapsulates the hardware addressing information, and static and dynamic configuration parameters of a GPIO port.
GPIOPortPermission	The GPIOPortPermission class defines permissions for GPIO port access.
PinEvent	The PinEvent class encapsulates GPIO pin value changes.
PortEvent	The PortEvent class encapsulates GPIO port value changes.

Package jdk.dio.gpio Description

Interfaces and classes for reading and writing from/to GPIO (General Purpose Input Output) pins and ports of the device.

A GPIO port is a platform-defined or an ad-hoc grouping of GPIO pins that may be configured for output or input. Note that whether GPIO pins that are part of a platform-defined GPIO port can be retrieved and controlled individually as GPIOPin instances depends on the hardware and platform configuration (and especially whether the GPIO pins can be shared through different abstractions).

In order to use a specific pin or port, an application should first open and obtain and obtain a GPIOPin instance or GPIOPort instance, respectively, for the pin or port it wants to use using its numerical ID, name, type (interface) and/or properties:

• Using its ID

   GPIOPin pin = (GPIOPin) DeviceManager.open(1);
   GPIOPort port = (GPIOPort) DeviceManager.open(0);
   

• Using its name and interface

   GPIOPin pin = (GPIOPin) DeviceManager.open("LED_PIN", GPIOPin.class, null);
   GPIOPort port = (GPIOPort) DeviceManager.open("LCD_DATA_PORT", GPIOPort.class, null);
   

Once a pin opened, an application can obtain the current value of a GPIO pin by calling the GPIOPin.getValue method and set its value by calling the GPIOPin.setValue method.
Once a port opened, an application can obtain the current value of a GPIO port by calling the GPIOPort.getValue method and set its value by calling the GPIOPort.setValue method.

 pin.setValue(true);
 port.setValue(0xFF);
 

When done, the application should call the GPIOPin.close or GPIOPort.close method to close the pin or port, respectively.

 pin.close();
 port.close();
 

The following sample code gives an example of using the GPIO API. It shows how to control GPIO Pins. It registers a pin listener for the GPIO input pin a switch button is attached to. When the button is pressed the listener is notified to turn the LED on or off by setting accordingly the GPIO output pin the LED is attached to.

 try (GPIOPin switchPin = (GPIOPin) DeviceManager.open(1); GPIOPin ledPin = (GPIOPin) DeviceManager.open(3)) {
     switchPin.setInputListener(new PinListener() {
 
         public void valueChanged(PinEvent event) {
             try {
                 ledPin.setValue(event.getValue()); // turn LED on or off
             } catch (IOException ioe) {
                 // handle exception
             }
         }
     });
     // perform some other computation
 } catch (IOException ioe) {
     // handle exception
 }
 

Note that the preceding example is using a try-with-resources statement and that the GPIOPin.close method is automatically invoked by the platform at the end of the statement.

Note that the underlying platform configuration may allow for some GPIO pins or ports to be set by an application for either output or input while others may be used for input only or output only and that their direction can not be changed by an application. Note also that asynchronous notification of pin or port value changes is only loosely tied to hardware-level interrupt requests. The platform does not guarantee notification in a deterministic/timely manner.

Because of performance issue, procedures handling GPIO pins, and especially event listeners, should be implemented to be as fast as possible.

Unless otherwise noted, passing a null argument to a constructor or method in any class or interface in this package will cause a NullPointerException to be thrown.