jdk.dio.gpio

Interface GPIOPin

All Superinterfaces:

java.lang.AutoCloseable, java.nio.channels.Channel, java.io.Closeable, Device<GPIOPin>

public interface GPIOPin
extends Device<GPIOPin>

The GPIOPin interface provides methods for controlling a GPIO pin.

A GPIO pin may be identified by the numeric ID and by the name (if any defined) that correspond to its registered configuration. A GPIOPin instance can be opened by a call to one of the DeviceManager.open(id,...) methods using its ID or by a call to one of the DeviceManager.open(name,...) methods using its name. When a GPIOPin instance is opened with an ad-hoc GPIOPinConfig configuration (which includes its hardware addressing information) using one of the DeviceManager.open(config,...) methods it is not assigned any ID nor name.

A GPIO pin may be configured for output or input. Output pins are both writable and readable while input pins are only readable.

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

An application can either monitor a GPIO pin value changes using polling or can register a PinListener instance which will get asynchronously notified of any pin value changes. To register a PinListener instance, the application must call the setInputListener method. The registered listener can later on be removed by calling the same method with a null listener parameter. Asynchronous notification is only supported for GPIO pin configured for input. An attempt to set a listener on a GPIO pin configured for output will result in an UnsupportedOperationException being thrown.

When an application is no longer using a GPIO pin it should call the close method to close the GPIO pin. Any further attempt to set or get the value of a GPIO pin which has been closed will result in a ClosedDeviceException been thrown.

The initial direction of a GPIO pin which may be used for output or input as well as the initial value of a GPIO pin set for output is configuration-specific. An application should always initially set the GPIO pin's direction; or first query the GPIO pin's direction then set it if necessary.

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

Since:

1.0

See Also:

PinListener, GPIOPinPermission

Field Summary

Fields

Modifier and Type	Field and Description
static int	INPUT Input port direction.
static int	OUTPUT Output port direction.

Fields inherited from interface jdk.dio.Device

BIG_ENDIAN, LITTLE_ENDIAN, MIXED_ENDIAN

Method Summary

Methods

Modifier and Type	Method and Description
int	getDirection() Returns the current direction of this GPIO pin.
int	getTrigger() Returns the current pin interrupt trigger.
boolean	getValue() Returns the current value of this GPIO pin.
void	setDirection(int direction) Sets this GPIO pin for output or input.
void	setInputListener(PinListener listener) Registers a PinListener instance which will get asynchronously notified when this GPIO pin's value changes and according to the current trigger mode (see getTrigger).
void	setTrigger(int trigger) Sets this GPIO pin trigger mode.
void	setValue(boolean value) Sets the value of this GPIO pin.

Methods inherited from interface jdk.dio.Device

close, getByteOrder, getDescriptor, isOpen, tryLock, unlock

Field Detail

INPUT

static final int INPUT

Input port direction.

See Also:

Constant Field Values

OUTPUT

static final int OUTPUT

Output port direction.

See Also:

Constant Field Values

Method Detail

getDirection

int getDirection()
                 throws java.io.IOException,
                        UnavailableDeviceException,
                        ClosedDeviceException

Returns the current direction of this GPIO pin. If the direction was not set previously using setDirection the device configuration-specific default value is returned.

Returns:

OUTPUT if this GPIO pin is currently set as output; INPUT otherwise (the GPIO pin is set as input).

Throws:

java.io.IOException - if some other I/O error occurs.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.

getTrigger

int getTrigger()
               throws java.io.IOException,
                      UnavailableDeviceException,
                      ClosedDeviceException

Returns the current pin interrupt trigger. If the trigger mode was not set previously using setTrigger the device configuration-specific default value is returned. Setting the trigger mode to GPIOPinConfig.TRIGGER_NONE disables the notification of the PinListener instance (see setInputListener without unregistering it. The value returned by this method is unaffected by changes of the direction on a bidirectional GPIO pin.

Returns:

the current pin interrupt trigger, one of: GPIOPinConfig.TRIGGER_NONE, GPIOPinConfig.TRIGGER_FALLING_EDGE, GPIOPinConfig.TRIGGER_RISING_EDGE , GPIOPinConfig.TRIGGER_BOTH_EDGES, GPIOPinConfig.TRIGGER_HIGH_LEVEL, GPIOPinConfig.TRIGGER_LOW_LEVEL, GPIOPinConfig.TRIGGER_BOTH_LEVELS; GPIOPinConfig.TRIGGER_NONE if this GPIO pin is configured for output-only.

Throws:

java.io.IOException - if some other I/O error occurs.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.

getValue

boolean getValue()
                 throws java.io.IOException,
                        UnavailableDeviceException,
                        ClosedDeviceException

Returns the current value of this GPIO pin. If the value was not set previously using setValue the device configuration-specific default value is returned.

This method can be called on both output and input pins.

Returns:

true if this pin is currently high.

Throws:

java.io.IOException - if an I/O error occurred such as the pin is not readable.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.

setDirection

void setDirection(int direction)
                  throws java.io.IOException,
                         UnavailableDeviceException,
                         ClosedDeviceException

Sets this GPIO pin for output or input. The direction can only be set to INPUT if the GPIO pin is configured for input-only (see GPIOPinConfig.DIR_INPUT_ONLY) or is configured as bidirectional (see GPIOPinConfig.DIR_BOTH_INIT_INPUT and GPIOPinConfig.DIR_BOTH_INIT_OUTPUT). The direction can only be set to OUTPUT if the GPIO pin is configured for output-only (see GPIOPinConfig.DIR_OUTPUT_ONLY) or is configured as bidirectional (see GPIOPinConfig.DIR_BOTH_INIT_INPUT and GPIOPinConfig.DIR_BOTH_INIT_OUTPUT). The value returned by getTrigger is unaffected by changes of the direction on a bidirectional GPIO pin.

Parameters:

direction - OUTPUT for output; INPUT for input.

Throws:

java.io.IOException - if some other I/O error occurs.

java.lang.UnsupportedOperationException - if this GPIO pin cannot be configured for the desired direction.

java.lang.IllegalArgumentException - if direction is not equal to OUTPUT or INPUT.

java.lang.SecurityException - if the caller does not have the required permission.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.

setTrigger

void setTrigger(int trigger)
                throws java.io.IOException,
                       UnavailableDeviceException,
                       ClosedDeviceException

Sets this GPIO pin trigger mode. Setting the trigger mode to GPIOPinConfig.TRIGGER_NONE disables the notification of the PinListener instance (see setInputListener without unregistering it.

Parameters:

trigger - the interrupt trigger events, one of: GPIOPinConfig.TRIGGER_NONE, GPIOPinConfig.TRIGGER_FALLING_EDGE, GPIOPinConfig.TRIGGER_RISING_EDGE, GPIOPinConfig.TRIGGER_BOTH_EDGES, GPIOPinConfig.TRIGGER_HIGH_LEVEL , GPIOPinConfig.TRIGGER_LOW_LEVEL, GPIOPinConfig.TRIGGER_BOTH_LEVELS.

Throws:

java.io.IOException - if an IO error occurred.

java.lang.UnsupportedOperationException - if this GPIO pin is currently configured for output or cannot otherwise be configured with the desired trigger mode.

java.lang.IllegalArgumentException - if trigger is not one of the defined values.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.

setInputListener

void setInputListener(PinListener listener)
                      throws java.io.IOException,
                             ClosedDeviceException

Registers a PinListener instance which will get asynchronously notified when this GPIO pin's value changes and according to the current trigger mode (see getTrigger). Notification will automatically begin after registration completes.

If this GPIOPin is open in DeviceManager.SHARED access mode and if this GPIOPin is currently configured for input, the listeners registered by all the applications sharing the underlying GPIO pin will get notified when its value changes.

A listener can only be registered for a GPIO pin currently configured for input.

If listener is null then the previously registered listener is removed.

Only one listener can be registered at a particular time.

Parameters:

listener - the PinListener instance to be notified when this GPIO pin's value changes.

Throws:

java.io.IOException - if some other I/O error occurs.

java.lang.UnsupportedOperationException - if this GPIO pin is currently configured for output.

java.lang.IllegalStateException - if listener is not null and a listener is already registered.

ClosedDeviceException - if the device has been closed.

setValue

void setValue(boolean value)
              throws java.io.IOException,
                     UnavailableDeviceException,
                     ClosedDeviceException

Sets the value of this GPIO pin.

An attempt to set the value on a GPIO pin currently configured for input will result in a UnsupportedOperationException being thrown.

Parameters:

value - the new pin value: true for high, false for low.

Throws:

java.lang.UnsupportedOperationException - if trying to set the value for pin configured for input.

java.io.IOException - if an I/O error occurred such as the pin is not writable.

UnavailableDeviceException - if this device is not currently available - such as it is locked by another application.

ClosedDeviceException - if the device has been closed.