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[New] Added section on Java API to README

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Robert von Burg 2016-02-12 12:54:20 +01:00
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@ -12,6 +12,51 @@ Features are:
If you have any issues, don't hesitate to add an issue to the GitHub project, write me an e-mail (eitch@eitchnet.ch) or reach me on Twitter!
## Java API
Before trying to use the Java API and wondering why it does not work, be very careful to ensure that the GPIOs are properly exported to userspace by using a device tree overlay and then using the `/sys/class/gpio/export` file to export the GPIO to userspace.
The Java API is simple and requires no configuration files. Everything is done programmitically. The main object is the `GpioBridge` instance which is retrieved as follows:
<pre>
GpioBridge gpioBridge = GpioBridge.getInstance();
</pre>
With a reference to the `GpioBridge`, `GPIO` objects can be retrieved by their `Pin` enum and a `Direction` as follows:
<pre>
GpioBridge gpioBridge = GpioBridge.getInstance();
Gpio pin8_07 = gpioBridge.getGpio(Pin.P8_07, Direction.IN);
</pre>
The `GpioBridge.getGpio()`-method will throw an exception if:
* the requested direction does not correspond to the direction configured in the kernel's exported pin
* the file permissions are not set so that the Java process can access the file (read access for input pin, write access for output pin.
### Reading Input Pins
To read the current signal of a pin use the `GpioBridge.readValue()`-method:
<pre>
GpioBridge gpioBridge = GpioBridge.getInstance();
Gpio pin8_07 = gpioBridge.getGpio(Pin.P8_07, Direction.IN);
Signal currentSignal = gpioBridge.readValue(pin8_07);
System.out.println(pin8_07 + " currently has signal " + currentSignal);
</pre>
### Writing Output Pins
To write the signal of a pin use the `GpioBridge.writeValue()`-method:
<pre>
GpioBridge gpioBridge = GpioBridge.getInstance();
Gpio pin8_08 = gpioBridge.getGpio(Pin.P8_08, Direction.OUT);
gpioBridge.writeValue(pin8_08, Signal.HIGH);
System.out.println("Set signal of " + pin8_08 + " to " + Signal.HIGH);
</pre>
### Observing Input Pins
To be notified of changes to an input GPIO, register a `GpioSignalListener`:
<pre>
GpioBridge gpioBridge = GpioBridge.getInstance();
Gpio pin8_07 = gpioBridge.getGpio(Pin.P8_07, Direction.IN);
gpioBridge.register(pin8_07, gpio -> System.out.println("Signal of "+pin8_07 + " has changed to " + gpio.getSignal()));
</pre>
## Setup BeagleBone
* Copy the scripts and files to the BeagleBone:
<pre>