Package com.pi4j.wiringpi

Class GpioUtil

java.lang.Object

com.pi4j.wiringpi.GpioUtil

public class GpioUtil
extends Object

This utility class is provided to export, unexport, and manipulate pin direction.

Before using the Pi4J library, you need to ensure that the Java VM in configured with access to the following system libraries:

• pi4j
• wiringPi

This library depends on the wiringPi native system library. (developed by Gordon Henderson @ http://wiringpi.com/)

Author:

Robert Savage (http://www.savagehomeautomation.com)

See Also:

https://pi4j.com/, http://wiringpi.com/

Field Summary

Fields

Modifier and Type	Field	Description
static int	DIRECTION_HIGH	GPIO PIN DIRECTION
static int	DIRECTION_IN	GPIO PIN DIRECTION
static int	DIRECTION_LOW	GPIO PIN DIRECTION
static int	DIRECTION_OUT	GPIO PIN DIRECTION
static int	EDGE_BOTH	GPIO PIN EDGE DETECTION
static int	EDGE_FALLING	GPIO PIN EDGE DETECTION
static int	EDGE_NONE	GPIO PIN EDGE DETECTION
static int	EDGE_RISING	GPIO PIN EDGE DETECTION

Method Summary

Modifier and Type	Method	Description
static void	enableNonPrivilegedAccess()	This method is used to enable non-privileged access to the GPIO pins on to system.
static void	export(int pin, int direction)	This method will export the selected GPIO pin.
static int	getDirection(int pin)	This method will get the selected GPIO pin's export direction.
static int	getEdgeDetection(int pin)	This method will get the selected GPIO pin's edge detection setting.
static boolean	isExported(int pin)	This method determines if the requested GPIO pin is already exported.
static int	isPinSupported(int pin)	This method will return a value of '1' if the pin is supported
static boolean	isPrivilegedAccessRequired()	This method will return a value of '1' if Privileged access is required.
static boolean	setDirection(int pin, int direction)	This method will set the selected GPIO pin's export direction.
static boolean	setEdgeDetection(int pin, int edge)	This method will set the selected GPIO pin's edge detection.
static void	unexport(int pin)	This method will unexport the selected GPIO pin.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DIRECTION_IN

public static final int DIRECTION_IN

GPIO PIN DIRECTION

GPIO pin constant for IN direction for reading pin states

See Also:

export(int,int), setDirection(int,int), getDirection(int), Constant Field Values

DIRECTION_OUT

public static final int DIRECTION_OUT

GPIO PIN DIRECTION

GPIO pin constant for OUT direction for writing digital pin states (0/1).

See Also:

export(int,int), setDirection(int,int), getDirection(int), Constant Field Values

DIRECTION_HIGH

public static final int DIRECTION_HIGH

GPIO PIN DIRECTION

GPIO pin constant for OUT direction with an initial default HIGH value for writing digital pin states (0/1).

See Also:

export(int,int), setDirection(int,int), getDirection(int), Constant Field Values

DIRECTION_LOW

public static final int DIRECTION_LOW

GPIO PIN DIRECTION

GPIO pin constant for OUT direction with an initial default LOW value for writing digital pin states (0/1).

See Also:

export(int,int), setDirection(int,int), getDirection(int), Constant Field Values

EDGE_NONE

public static final int EDGE_NONE

GPIO PIN EDGE DETECTION

This constant is provided as an edge detection mode for use with the 'edge' method. This constants instructs the edge detection to be disabled.

See Also:

setEdgeDetection(int,int), Constant Field Values

EDGE_BOTH

public static final int EDGE_BOTH

GPIO PIN EDGE DETECTION

This constant is provided as an edge detection mode for use with the 'edge' method. This constants instructs the edge detection to only look for rising and falling pins states; pins changing from LOW to HIGH or HIGH to LOW.

See Also:

setEdgeDetection(int,int), Constant Field Values

EDGE_RISING

public static final int EDGE_RISING

GPIO PIN EDGE DETECTION

This constant is provided as an edge detection mode for use with the 'edge' method. This constants instructs the edge detection to only look for rising pins states; pins changing from LOW to HIGH.

See Also:

setEdgeDetection(int,int), Constant Field Values

EDGE_FALLING

public static final int EDGE_FALLING

GPIO PIN EDGE DETECTION

This constant is provided as an edge detection mode for use with the 'edge' method. This constants instructs the edge detection to only look for falling pins states; pins changing from HIGH to LOW.

See Also:

setEdgeDetection(int,int), Constant Field Values

Method Detail

export

public static void export(int pin,
                          int direction)
                   throws RuntimeException

This method will export the selected GPIO pin.

This method required root permissions access.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

direction - pin direction

Throws:

RuntimeException

See Also:

DIRECTION_IN, DIRECTION_OUT

unexport

public static void unexport(int pin)
                     throws RuntimeException

This method will unexport the selected GPIO pin.

This method required root permissions access.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

Throws:

RuntimeException

isExported

public static boolean isExported(int pin)
                          throws RuntimeException

This method determines if the requested GPIO pin is already exported.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

Returns:

A return value of '0' represents that the pin is not exported. A return value of '1' represents that the pin is exported.

Throws:

RuntimeException

setEdgeDetection

public static boolean setEdgeDetection(int pin,
                                       int edge)
                                throws RuntimeException

This method will set the selected GPIO pin's edge detection. Edge detection instructs when the hardware GPIO changes raise interrupts on the system.

NOTE: Calling this method will automatically export the pin and set the pin direction to INPUT. This method required root permissions access.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

edge - The edge condition to detect: none, rising, falling, or both. The following constants are provided for use with this parameter:

• EDGE_NONE
• EDGE_BOTH
• EDGE_RISING
• EDGE_FALLING

Returns:

A return value of '0' represents success. Errors are returned as negative numbers.

Throws:

RuntimeException

See Also:

EDGE_NONE, EDGE_BOTH, EDGE_RISING, EDGE_FALLING

getEdgeDetection

public static int getEdgeDetection(int pin)
                            throws RuntimeException

This method will get the selected GPIO pin's edge detection setting. Edge detection instructs when the hardware GPIO changes raise interrupts on the system.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

Returns:

The edge condition detected on the selected pin: none, rising, falling, or both. The following constants are provided for use with this parameter:

• EDGE_NONE
• EDGE_BOTH
• EDGE_RISING
• EDGE_FALLING

Throws:

RuntimeException

See Also:

EDGE_NONE, EDGE_BOTH, EDGE_RISING, EDGE_FALLING

setDirection

public static boolean setDirection(int pin,
                                   int direction)
                            throws RuntimeException

This method will set the selected GPIO pin's export direction.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

direction - The export direction to apply: IN, OUT. The following constants are provided for use with this parameter:

• DIRECTION_IN
• DIRECTION_OUT

Returns:

A return value of '0' represents success. Errors are returned as negative numbers.

Throws:

RuntimeException

See Also:

DIRECTION_IN, DIRECTION_OUT

getDirection

public static int getDirection(int pin)
                        throws RuntimeException

This method will get the selected GPIO pin's export direction.

Parameters:

pin - GPIO pin number (not header pin number; not wiringPi pin number)

Returns:

The GPIO pin's configured export direction is returned: IN (0), OUT (1). The following constants are provided for use with this parameter:

• DIRECTION_IN
• DIRECTION_OUT

Throws:

RuntimeException

See Also:

DIRECTION_IN, DIRECTION_OUT

isPinSupported

public static int isPinSupported(int pin)
                          throws RuntimeException

This method will return a value of '1' if the pin is supported

Parameters:

pin - pin number

Returns:

'1' is the pin is supported, else '0'

Throws:

RuntimeException

isPrivilegedAccessRequired

public static boolean isPrivilegedAccessRequired()
                                          throws RuntimeException

This method will return a value of '1' if Privileged access is required. This method will return a value of '0' if Privileged access is NOT required. Privileged access is required if any of the the following conditions are not met: - You are running with Linux kernel version 4.1.7 or greater - The Device Tree is enabled - The 'bcm2835_gpiomem' kernel module loaded. - Udev rules are configured to permit write access to '/sys/class/gpio/**'

Returns:

'true' if privileged access is required; else returns 'false'.

Throws:

RuntimeException

enableNonPrivilegedAccess

public static void enableNonPrivilegedAccess()
                                      throws RuntimeException

This method is used to enable non-privileged access to the GPIO pins on to system. This method will throw a runtime exception if privileged access is required. You can test for required access using the 'isPrivilegedAccessRequired()' method. Please note when non-privileged access is enabled, you will not be able to use any hardware PWM or CLOCK functions.

Throws:

RuntimeException