The GPIO controller interface

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The simplest interface to the GPIO connector is the singleton rpihw::gpio. It is a structure that accurately reproduces the connector behavior, without any kind of abstraction. Once instantiated, you have several methods to manage the GPIOs of your Raspberry Pi.

• Set the mode of a GPIO
• Set the state of an ouput pin
• Read the state of an input pin
• Enable pull-up/down resistor of a input pin

Set the mode of a GPIO

The method setup allows you to set the working mode of a GPIO, by deciding if it must be used as output or input pin. The needed arguments are the GPIO number and the new working mode to be set.

// Use the Rpi-hw namespace
using namespace rpihw;

// Get the GPIO controller interface 
gpio &io = gpio::get();

// Set the GPIO #11 as output pin
io.setup( 11, gpio::OUTPUT );

// Set the GPIO #9 as input pin
io.setup( 9, gpio::INPUT );

Set the state of an ouput pin

You can change the logic state of a output pin with the method write. It, in addition to the number of GPIO, takes an boolean parameter representing the new logic state.

// Set the GPIO #11 to the high level
io.write( 11, gpio::HIGH );

// Set the GPIO #11 to the low level
io.write( 11, gpio::LOW );

// Set the GPIO #11 to the high level
io.write( 11, 1 );

// Set the GPIO #11 to the low level
io.write( 11, 0 );

Read the state of an input pin

With the method read you can read the logic state of an input pin.

// Read the logic state of the GPIO #9
bool state = io.read(9);

Enable pull-up/down resistor of a input pin

Raspberry Pi's GPIOs have internal pull-up or pull-down resistor used to ensure the logic level of an input pin in case of open circuit or high-impedance. You can enable this resistor on an input pin using the method setPullUpDown.

// Use the pull-up resistor on the GPIO #9
io.setPullUpDown( 9, gpio::PULL_UP );

// Use the pull-down resistor on the GPIO #9
io.setPullUpDown( 9, gpio::PULL_DOWN );

// Disable the pull-up/down resistors on the GPIO #9
io.setPullUpDown( 9, gpio::PUD_OFF );