Linux Userspace GPIO Library
============================

 * Export and Unexport GPIO pins
 * Interrupt support (*)
 * Hardware-neutral rewrite of NoccyLabs RaspIO 
 * Compatible with psr/logs LoggerInterface for logging

## Interrupts

*NOTE: Not implemented!*

For interrupts to work, you need to first bind the interrupt handler, and then
make sure to call on `Gpio#refresh()` every cycle to poll the interrupt flag on
the selected pins. This is because the `select()` function is used.

    $gpio = new Gpio();

    // Set the handler on the Gpio object
    $gpio->setInterruptHandler($gpio[4], function() { ... });
    // Or like this on the GpioPin.
    $gpio[4]
        ->setEdge("rising")
        ->setHandler(function() { ... });
    
    while (..) {
        ..
        $gpio->refresh();
    }

You can also be risky and use php ticks and timerfuncs (although that might not
be portable/supported/efficient/a good idea):

    declare(ticks=5);
    
    $gpio = new Gpio();
    
    $gpiotick = new GpioTickHandler();
    $gpiotick->registerGpio($gpio);
    
    // The interrupts will now be polled approx every 5th php vm "tick"

## Devices

    $lcd = new NoccyLabs\Gpio\Device\Display\Pcd8544Device;
    // Set I/O pins
    $lcd->res = $gpio[4];
    $lcd->dc  = $gpio[8];
    ...
    // Activate the device
    $lcd->activate();
    // Clear and draw text
    $lcd->clear();
    $lcd->writeAt(0,0,"Hello World");
    echo $lcd->getRows(); // 5
    echo $lcd->getCols(); // 19

### LCD Bridge

The LCD bridge will be able to bridge any device class implementing `LcdDeviceInterface`
to stdin or a named pipe. This basically creates a user-space daemon to interface with
the display without having to fiddle with bits.

    $ lcdbridge -t pcd8544 --stdin
    CLR
    LOC 0 0
    FONT 0
    OUT Hello World
    ^C
    $ 

Commands should include:

 * `CLR` clears the display (`LcdDeviceInterface#clear()`)
 * `LOC n m` moves the cursor to line n column m (0-indexed) (`LcdDeviceInterface#setCursorPos(n,m)`) 
 * `FONT n` loads the default font (0) or a custom font file (`LcdDeviceInterface#setFont()`)
 * `OUT` Write text to the display (`LcdDeviceInterface#write()`)