WiringPi-Perl example

Posted 08-12-2013 at 09:11 PM by drask
Updated 08-16-2013 at 01:11 PM by drask

This is a Raspberry Pi project I did a few months ago and meant to post somewhere. There is a Perl interface to the WiringPi module. It's available from https://github.com/WiringPi/WiringPi-Perl. Unfortunately it doesn't come with any examples, but the WiringPi module comes with some nice examples. Unfortunately they are all written in C and it can take some trial and error to translate and I never found any translations of the examples online, or any WiringPi-Perl specific examples.

Here is my version of test1.c translated to Perl (flashes a series of 8 LEDs back and forth like Knight Rider's grill or a 1970's Cylon eyeball, a button allows you to speed up the action):

Code:

#!/usr/bin/perl
#test1.pl
use wiringpi;
use constant {
	OUTPUT=>1,
	INPUT=>0,
	HIGH=>1,
	LOW=>0
};

$SIG{'INT'}=\&safe_exit;
$SIG{'QUIT'}=\&safe_exit;
$SIG{__DIE__}=\&safe_exit;

print("Raspberry Pi wiringPi test program\n");
if( wiringpi::wiringPiSetup()==-1 ){
	die 1;
}

for( my $pin=0;$pin<8;++$pin ){
	wiringpi::pinMode($pin,OUTPUT);
}

wiringpi::pinMode(8,INPUT);

@data=(
		[0,1,1],
		[1,1,1],
	[0,0,0],[2,1,1],
	[1,0,0],[3,1,1],
	[2,0,0],[4,1,1],
	[3,0,0],[5,1,1],
	[4,0,0],[6,1,1],
	[5,0,0],[7,1,1],
	[6,0,1],
	[7,0,1],
		[7,1,1],
		[6,1,1],
	[7,0,0],[5,1,1],
	[6,0,0],[4,1,1],
	[5,0,0],[3,1,1],
	[4,0,0],[2,1,1],
	[3,0,0],[1,1,1],
	[2,0,0],[0,1,1],
	[1,0,1],
	[0,0,1],
	[9,9,9]
);

my $inc=0;

while( 1==1 ){
	my( $pin,$state,$duration )=@{$data[$inc]};
	if( $pin+$state+$duration==27 ){
		$inc=0;
		next;
	}
	wiringpi::digitalWrite($pin,$state);
	if( wiringpi::digitalRead(8)==LOW ){
		wiringpi::delay($duration*10);
	}else{
		wiringpi::delay( $duration*100 );
	}
	++$inc;
}

# this just turns off all the LEDs when you exit the script
sub safe_exit{
	for( my $pin=0;$pin<8;++$pin ){
		wiringpi::digitalWrite($pin,LOW);
	}
	exit 1;
}

Unfortunately, you have to run this as root, which seems to common to all WiringPi versions. After compiling the C code, you can suid the program and just run it directly as a normal user, so you can compile it and then let your kids run it, but working in Perl is fun.

I'll attach a link to a schematic in the next couple of days, since I felt like the original script could have used one (the schematic is the same for both test1.c and test1.pl). I'm using a Pi Cobbler from Adafruit to connect the Pi to my breadboard, which has made test wiring much easier for me.

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