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Steve Bertrand


RPi::WiringPi - Perl interface to Raspberry Pi's board, GPIO, LCDs and other various items


    use RPi::WiringPi;
    use RPi::Const qw(:all);

    my $pi = RPi::WiringPi->new;

    # pin

    my $pin = $pi->pin(5);

    my $num = $pin->num;
    my $mode = $pin->mode;
    my $state = $pin->read;

    # analog to digital converter (ADS1115)

    my $adc = $pi->adc;
    # read channel A0 on the ADC

    my $v = $adc->volts(0);
    my $p = $adc->percent(0);

    # analog to digital converter (MCP3008)

    my $adc = $pi->adc(model => 'MCP3008', channel => 0);

    print $adc->raw(0);
    print $adc->percent(0);

    # I2C

    my $device_addr = 0x7c;

    my $i2c_device = $pi->i2c($device_addr);

    my $register = 0x0A;

    $i2c_device->write_block([55, 29, 255], $register);

    my $byte = $i2c_device->read;

    my @bytes = $i2c_device->read_block;

    # SPI

    my $channel = 0; # SPI channel /dev/spidev0.0

    my $spi = $pi->spi($channel);

    my $buf = [0x01, 0x02];
    my $len = scalar @$buf;

    my @read_bytes = $spi->rw($buf, $len);

    # Serial

    my $dev  = "/dev/ttyS0";
    my $baud = 115200;

    my $ser = $pi->serial($dev, $baud);


    my $char = $ser->getc;

    $ser->puts("hello, world!");

    my $num_bytes = 12;
    my $str  = $ser->gets($num_bytes);


    my $bytes_available = $ser->avail;

    # digital to analog converter (DAC)

    my $dac_cs_pin = $pi->pin(29);
    my $spi_chan = 0;

    my $dac = $pi->dac(
        model   => 'MCP4922',
        channel => $spi_chan,
        cs      => $dac_cs_pin

    my ($dacA, $dacB) = (0, 0);

    $dac->set($dacA, 4095); # 100% output
    $dac->set($dacB, 0);    # 0% output

    # digital potentiometer

    my $cs = 18;     # GPIO pin connected to dpot CS pin
    my $channel = 0; # SPI channel /dev/spidev0.0

    my $dpot = $pi->dpot($cs, $channel);

    # set to 50% output


    # shutdown (sleep) the potentiometer


    # shift register
    my ($base, $num_pins, $data, $clk, $latch)
      = (100, 8, 5, 6, 13);

        $base, $num_pins, $data, $clk, $latch

    # now we can access the new 8 pins of the
    # register commencing at new pin 100-107

    for (100..107){
        my $pin = $pi->pin($_);

    # BMP180 barometric pressure sensor
    my $base = 300; 

    my $bmp = $pi->bmp($base);

    my $farenheit = $bmp->temp;
    my $celcius   = $bmp->temp('c');
    my $pressure  = $bmp->pressure; # kPa

    # DHT11 temperature/humidity sensor

    my $sensor_pin = 21;

    my $env = $pi->hygrometer($sensor_pin);

    my $humidity  = $env->humidity;
    my $temp      = $env->temp; # celcius
    my $farenheit = $env->temp('f');

    # GPS (requires gpsd to be installed and running)

    my $gps = $pi->gps;

    print $gps->tpv('lat')   . "\n";
    print $gps->tpv('lon')   . "\n";
    print $gps->tpv('speed') . "\n";
    print $gps->direction    . "\n";

    # LCD

    my $lcd = $pi->lcd(...);

    # first column, first row
    $lcd->position(0, 0); 
    $lcd->print("hi there!");

    # first column, second row
    $lcd->position(0, 1);
    $lcd->print("pin $num... mode: $mode, state: $state");



    # ultrasonic distance sensor

    my $trig_pin = 23;
    my $echo_pin = 24;

    my $ruler = $pi->hcsr04($trig_pin, $echo_pin);

    my $inches = $sensor->inch;
    my $cm     = $sensor->cm;
    my $raw    = $sensor->raw;

    # servo

    my $pin_num = 18;

    my $servo = $pi->servo($pin_num);

    $servo->pwm(150); # centre position
    $servo->pwm(50);  # left position
    $servo->pwm(250); # right position

    # stepper motor

    my $sm = $pi->stepper_motor(
        pins => [12, 16, 20, 21]

    $sm->cw(180);   # turn clockwise 180 degrees
    $sm->ccw(240);  # turn counter-clockwise 240 degrees


This is the root module for the RPi::WiringPi system. It interfaces to a Raspberry Pi board, its accessories and its GPIO pins via the wiringPi library through the Perl wrapper WiringPi::API module, and various other custom device specific modules.

wiringPi must be installed prior to installing/using this module (v2.36+).

We always and only use the GPIO pin numbering scheme. These are the pin numbers that are printed on the Pi board itself.

This module is essentially a 'manager' for the sub-modules (ie. components). You can use the component modules directly, but retrieving components through this module instead has many benefits. We maintain a registry of pins and other data. We also trap $SIG{__DIE__} and $SIG{INT}, so that in the event of a crash, we can reset the Pi back to default settings, so components are not left in an inconsistent state. Component modules do none of these things.

There are a basic set of constants that can be imported. See RPi::Const.

It's handy to have access to a pin mapping conversion chart. There's an excellent pin scheme map for reference at pinout.xyz. You can also run the pinmap command that was installed by this module, or wiringPi's gpio readall command.


See RPi::WiringPi::Core for utility/helper/hardware-specific methods that are imported into an RPi::WiringPi object.


Returns a new RPi::WiringPi object. We exclusively use the GPIO (Broadcom (BCM) GPIO) pin numbering scheme. These pin numbers are printed on the Pi's board itself.


    fatal_exit => $bool

Optional: We trap all die() calls and clean up for safety reasons. If a call to die() is trapped, by default, we clean up, and then exit(). Set fatal_exit to false (0) to perform the cleanup, and then continue running your script. This is for unit testing purposes only.


There are two different ADCs that you can select from. The default is the ADS1x15 series:


Returns a RPi::ADC::ADS object, which allows you to read the four analog input channels on an Adafruit ADS1xxx analog to digital converter.


The default (no parameters) is almost always enough, but please do review the documentation in the link above for further information, and have a look at the ADC tutorial section in this distribution.


You can also use an RPi::ADC::MCP3008 ADC.


    model => 'MCP3008'

Mandatory, String. The exact quoted string above.

    channel => $channel

Mandatory, Integer. 0 or 1 for the Pi's onboard hardware CS/SS CE0 and CE1 pins, or any GPIO number above 1 in order to use an arbitrary GPIO pin for the CS pin, and we'll do the bit-banging of the SPI bus automatically.


Returns a RPi::BMP180 object, which allows you to return the current temperature in farenheit or celcius, along with the ability to retrieve the barometric pressure in kPa.

dac(model => 'MCP4922')

Returns a RPi::DAC::MCP4922 object (supports all 49x2 series DACs). These chips provide analog output signals from the Pi's digital output. Please see the documentation of that module for further information on both the configuration and use of the DAC object.


    model => 'MCP4922'

Optional, String. The model of the DAC you're using. Defaults to MCP4922.

    channel => 0|1

Mandatory, Bool. The SPI channel to use.

    cs => Integer

Mandatory, Integer. A valid GPIO pin that the DAC's Chip Select is connected to.

There are a handful of other parameters that aren't required. For those, please refer to the RPi::DAC::MCP4922 documentation.

dpot($cs, $channel)

Returns a RPi::DigiPot::MCP4XXXX object, which allows you to manage a digital potentiometer (only the MCP4XXXX versions are currently supported).

See the linked documentation for full documentation on usage, or the RPi::WiringPi::FAQ for usage examples.


Returns a GPSD::Parse object, allowing you to track your location.

The GPS distribution requires gpsd to be installed and running. All parameters for the GPS can be sent in here and we'll pass them along. Please see the link above for the full documentation on that module.

hcsr04($trig, $echo)

Returns a RPi::HCSR04 ultrasonic distance measurement sensor object, allowing you to retrieve the distance from the sensor in inches, centimetres or raw data.



The trigger pin number, in GPIO numbering scheme.


The echo pin number, in GPIO numbering scheme.


Returns a RPi::DHT11 temperature/humidity sensor object, allows you to fetch the temperature (celcius or farenheit) as well as the current humidity level.

i2c($addr, [$device])

Creates a new RPi::I2C device object which allows you to communicate with the devices on an I2C bus.

See the linked documentation for full documentation on usage, or the RPi::WiringPi::FAQ for usage examples.

Aruino note: If using I2C with an Arduino, the Pi may speak faster than the Arduino can. If this is the case, try lowering the I2C bus speed on the Pi:



Returns a RPi::LCD object, which allows you to fully manipulate LCD displays connected to your Raspberry Pi.

Please see the linked documentation for information regarding the parameters required.


Returns a RPi::Pin object, mapped to a specified GPIO pin, which you can then perform operations on. See that documentation for full usage details.



Mandatory, Integer: The pin number to attach to.

serial($device, $baud)

Creates a new RPi::Serial object which allows basic read/write access to a serial bus.

See the linked documentation for full documentation on usage, or the RPi::WiringPi::FAQ for usage examples.

NOTE: Bluetooth on the Pi overlays the serial pins (14, 15) on the Pi. To use serial, you must disable bluetooth in the /boot/config.txt file:



This method configures PWM clock and divisor to operate a typical 50Hz servo, and returns a special RPi::Pin object. These servos have a left pulse of 50, a centre pulse of 150 and a right pulse of 250. On exit of the program (or a crash), we automatically clean everything up properly.



Mandatory, Integer: The pin number (technically, this *must* be 18 on the Raspberry Pi 3, as that's the only hardware PWM pin.


    my $servo = $pi->servo(18);

    $servo->pwm(50);  # all the way left
    $servo->pwm(250); # all the way right

shift_register($base, $num_pins, $data, $clk, $latch)

Allows you to access the output pins of up to four 74HC595 shift registers in series, for a total of eight new output pins per register. Numerous chains of four registers are permitted, each chain uses three GPIO pins.



Mandatory: Integer, represents the number at which you want to start referencing the new output pins attached to the register(s). For example, if you use 100 here, output pin 0 of the register will be 100, output 1 will be 101 etc.


Mandatory: Integer, the number of output pins on the registers you want to use. Each register has eight outputs, so if you have a single register in use, the maximum number of additional pins would be eight.


Mandatory: Integer, the GPIO pin number attached to the DS pin (14) on the shift register.


Mandatory: Integer, the GPIO pin number attached to the SHCP pin (11) on the shift register.


Mandatory: Integer, the GPIO pin number attached to the STCP pin (12) on the shift register.

spi($channel, $speed)

Creates a new RPi::SPI object which allows you to communicate on the Serial Peripheral Interface (SPI) bus with attached devices.

See the linked documentation for full documentation on usage, or the RPi::WiringPi::FAQ for usage examples.


Creates a new RPi::StepperMotor object which allows you to drive a 28BYJ-48 stepper motor with a ULN2003 driver chip.

See the linked documentation for full usage instructions and the optional parameters.


    pins => $aref

Mandatory, Array Reference: The ULN2003 has four data pins, IN1, IN2, IN3 and IN4. Send in the GPIO pin numbers in the array reference which correlate to the driver pins in the listed order.

    speed => 'half'|'full'

Optional, String: By default we run in "half speed" mode. Essentially, in this mode we run through all eight steps. Send in 'full' to double the speed of the motor. We do this by skipping every other step.

    delay => Float|Int

Optional, Float or Int: By default, between each step, we delay by 0.01 seconds. Send in a float or integer for the number of seconds to delay each step by. The smaller this number, the faster the motor will turn.


Please see RUNNING TESTS in the FAQ.


Steve Bertrand, <steveb@cpan.org>


Copyright (C) 2017,2018 by Steve Bertrand

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.18.2 or, at your option, any later version of Perl 5 you may have available.