iqb/gpio

GPIO library and test framework

PHP GPIO abstraction

GPIO abstraction using the linux sysfs interface, mainly for Raspberry PI., _(*1)

Installation

Just put the following in your composer.json file inside your project root. No stable version exists so far., _(*2)

"require": {
  "iqb/gpio": "*@dev"
}

Features

• Pin class: abstraction of a single GPIO pin
• LCD class: abstraction of a HD44780 compatible 16x2 display
• PinEmulator class: mock replacement for Pin class
• Emulator class: uses PinEmulators to make GPIO using software testable!

GPIO pin abstraction

The Pin class provides a simple interface to GPIO pins/ports. It uses the userspace GPIO interface provided by the linux kernel below /sys/class/gpio and so will obviously not work on other operating systems. It is developed on Raspbian Wheezy., _(*3)

The linux kernel identifies the GPIO pins by numbers. They can be found using the BCM value of the gpio readall (you need WiringPi for the command to exist)., _(*4)

namespace iqb\gpio;

// Will open the GPIO pin with BCM number 17 = physical pin 11
$pin = new Pin(17);

// A pin must be enabled so it can be used.
// Pin-consumers like the LCD class enable pins themselves when they use them 
$pin->enable();

// Pin is in output mode
$pin->setDirection(Pin::DIRECTION_OUT);

// and the pin is now enabled (sending a 1)
$pin->setValue(true);

// Pin is in input mode now
$pin->setDirection(Pin::DIRECTION_IN);

// Enable edge detection.
// This feature is required to detect changes of the value.
$pin->setEdge(Pin::EDGE_BOTH);

// Read the current value
$value = $pin->getValue();

// We can wait for a change of the pin value using stream_select()
// We need to initialize the file handle sets we want to monitor.
// Changes to GPIO pins are "exceptional" (out of band) events
// so we need the third set of handles.
$read = [];
$write = [];
$except = [$pin->getValueHandle()];
while (true) {
  if (-1 === stream_select($read, $write, $except, 60)) { continue; }

  echo "Value changed: " . ($pin->getValue() ? '1' : '0') . "\n";  
}

HD44780 compatible 16x2 display abstraction

This display is connected via 6 GPIO pins., _(*5)

namespace iqb\gpio;

// Create the display, the pins are the actual used pins from my personal project
// You don't need to enable the pins or set the direction,
// that is done by the LCD class.
$lcd = new LCD(
  new Pin(7),
  new Pin(8),
  new Pin(25),
  new Pin(24),
  new Pin(23),
  new Pin(18)
);

// Enable the pins, set the direction, send some magic commands to the display ...
$lcd->initialize();

// Write something in the first line
$lcd->writeString('abcdefghijklmnop', 1);
// Write something in the second line
$lcd->writeString('0123456789012345', 2);