# pwm.pl

use Time::HiRes qw( usleep);
use Inline C => Config => LIBS => '-lbcm2835';
use Inline C;

#
# Simple loops 10 times through some intensity values for
# the led.
#
# You can give a integer (0 .. 1024) on the command line
# to set the final brightness level at the end of the
# script.
#
# No secured in any way against bad input, errors, ...
#


print "start\n";

if (!pwm_prepare()) {

        print "prepare led succeeded\n";

        my @levels = (0,1,2,4,8,16,32,64,128,256,512,1024);

        for (my $i = 0; $i < 10; $i++) {

                foreach my $level (@levels) {

                        # print "level: $level\n";

                        pwm_set_led_intensity($level);
                        usleep(50000);

                }

        }

        pwm_set_led_intensity($ARGV[0]);

        pwm_clean();

        print "the end\n";

}


__END__
__C__

#include <stdio.h>
#include <bcm2835.h>

// PWM output on RPi Plug P1 pin 12 (which is GPIO pin 18)
// in alt fun 5.
// Note that this is the _only_ PWM pin available on the RPi IO headers
#define PIN RPI_GPIO_P1_12
// and it is controlled by PWM channel 0
#define PWM_CHANNEL 0
// This controls the max range of the PWM signal
#define RANGE 1024

int pwm_prepare();
void pwm_clean();
void pwm_set_led_intensity (int level);


int pwm_prepare()
{

    if (!bcm2835_init())
        return 1;

    // Set the output pin to Alt Fun 5, to allow PWM channel 0 to be output there
    bcm2835_gpio_fsel(PIN, BCM2835_GPIO_FSEL_ALT5);

    // Clock divider is set to 16.
    // With a divider of 16 and a RANGE of 1024, in MARKSPACE mode,
    // the pulse repetition frequency will be
    // 1.2MHz/1024 = 1171.875Hz
    bcm2835_pwm_set_clock(BCM2835_PWM_CLOCK_DIVIDER_16);
    bcm2835_pwm_set_mode(PWM_CHANNEL, 1, 1);
    bcm2835_pwm_set_range(PWM_CHANNEL, RANGE);

    return 0;

}

void pwm_clean()
{

    bcm2835_close();

    return;

}

void pwm_set_led_intensity (int level) {

        if (0 <= level && level <= 1024) {

                bcm2835_pwm_set_data(0,level);

        }

        return;

}