File Coverage

blib/lib/NexStarCtl.pm

Criterion	Covered	Total	%
statement	18	641	2.8
branch	0	238	0.0
condition	0	95	0.0
subroutine	6	66	9.0
pod	55	58	94.8
total	79	1098	7.1

#!/usr/bin/perl

########################################################
# NexCtl - NexStar control library
#
#
#		     (c)2013-2014 by Rumen G.Bogdanovski
########################################################

=head1 NAME

 NexStarCtl - API to control NexStar compatible telescopes

=head1 SYNOPSIS

 use NexStarCtl;

 my $port = open_telescope_port("/dev/XXX");
 if (!defined $port) {
	print "Can not open communication port.\n";
	exit;
 }

 # check if the mount is aligned
 if (tc_check_align($port)) {
 	print "The telescope is aligned.\n";
 } else {
 	print "The telescope is not aligned.\n";
 }

 # Read the stored coordinates of the location
 my ($lon,$lat) = tc_get_location_str($port);
 if (! defined($lon)) {
 	print "Telescope did not respond\n";
 	close_telescope_port($port);
 	exit;
 }
 print "Location coordinates:\n LON=$lon\n LAT=$lat\n";

 my ($date,$time,$tz,$dst) = tc_get_time_str($port);
 # ...
 # Do some other stuff
 # ...

 close_telescope_port($port);

=head1 DESCRIPTION

This module implements the serial commands supported by the Celestron NexStar hand control. This applies to the NexStar GPS,
NexStar GPS-SA, NexStar iSeries, NexStar SE Series, NexStar GT, CPC, SLT, Advanced-VX, Advanced-GT, and CGE mounts.

Communication to the hand control is 9600 bits/sec, no parity and one stop bit via the RS-232 port on the base of the
hand control.

For extended example how to use this perl module look in to the distribution folder for  nexstarctl/nexstarctl.pl.
This program is a complete console tool to control NexStar telesctopes based on NexStarCtl module.

=cut

package NexStarCtl;

use POSIX;
use Time::Local;
use strict;
use Exporter;

if ($^O eq "MSWin32") {
	eval "use Win32::SerialPort"; die $@ if $@;
} else {
	eval "use Device::SerialPort"; die $@ if $@;
}

our @ISA = qw(Exporter);
our @EXPORT = qw(
	VERSION

	DEG2RAD RAD2DEG
	notnum precess round
	d2hms d2dms d2dm dms2d hms2d
	dd2nex dd2pnex nex2dd pnex2dd

	get_model_name

	open_telescope_port
	close_telescope_port
	read_telescope

	tc_pass_through_cmd
	tc_check_align
	tc_goto_rade tc_goto_rade_p
	tc_goto_azalt tc_goto_azalt_p
	tc_get_rade tc_get_rade_p
	tc_get_azalt tc_get_azalt_p
	tc_sync_rade tc_sync_rade_p
	tc_goto_in_progress tc_goto_cancel
	tc_get_model
	tc_get_version
	tc_echo
	tc_get_location tc_get_location_str
	tc_get_time tc_get_time_str
	tc_set_time tc_set_location
	tc_get_tracking_mode tc_set_tracking_mode
	tc_slew_variable tc_slew_fixed
	tc_get_autoguide_rate tc_set_autoguide_rate
	tc_get_backlash tc_set_backlash

	pec_seek_index pec_index_found
	pec_record pec_record_complete
	pec_playback pec_get_playback_index
	pec_get_data_len pec_set_data pec_get_data

	TC_TRACK_OFF
	TC_TRACK_ALT_AZ
	TC_TRACK_EQ_NORTH
	TC_TRACK_EQ_SOUTH

	TC_DIR_POSITIVE
	TC_DIR_NEGATIVE

	TC_AXIS_RA_AZM
	TC_AXIS_DE_ALT

	PEC_START
	PEC_STOP
);

our $VERSION = "0.12";

use constant {
	TC_TRACK_OFF => 0,
	TC_TRACK_ALT_AZ => 1,
	TC_TRACK_EQ_NORTH => 2,
	TC_TRACK_EQ_SOUTH => 3,

	TC_DIR_POSITIVE => 1,
	TC_DIR_NEGATIVE => 0,

	TC_AXIS_RA_AZM => 1,
	TC_AXIS_DE_ALT => 0,

	_TC_DIR_POSITIVE => 6,
	_TC_DIR_NEGATIVE => 7,

	_TC_AXIS_RA_AZM => 16,
	_TC_AXIS_DE_ALT => 17,

	PEC_START => 1,
	PEC_STOP => 0,

	DEG2RAD => 3.1415926535897932384626433832795/180.0,
	RAD2DEG => 180.0/3.1415926535897932384626433832795
};

my %mounts = (
	1 => "NexStar GPS Series",
	3 => "NexStar i-Series",
	4 => "NexStar i-Series SE",
	5 => "CGE",
	6 => "Advanced GT",
	7 => "SLT",
	9 => "CPC",
	10 => "GT",
	11 => "NexStar 4/5 SE",
	12 => "NexStar 6/8 SE",
	14 => "CGEM",
	20 => "Advanced VX"
);

=head1 TELESCOPE COMMUNICATION

=over 8

=item open_telescope_port(port_name)

Opens a communication port to the telescope by name (like "/dev/ttyUSB0") and
returns it to be used in other functions. In case of error undef is returned.

=cut
sub open_telescope_port($) {
	my ($tty) = @_;

	my $port;
	if ($^O eq "MSWin32") {
		$port = new Win32::SerialPort($tty);
	} else {
		$port = new Device::SerialPort($tty);
	}
	if (! defined $port) {return undef;}
	#$port->debug(1);
	$port->baudrate(9600);
	$port->parity("none");
	$port->databits(8);
	$port->stopbits(1);
	$port->datatype('raw');
	$port->write_settings;
	$port->read_char_time(0);     # don't wait for each character
	$port->read_const_time(4000); # 4 second per unfulfilled "read" call
	return $port;
}

=item read_telescope(port, len)

Reads data from the telescope. On error or in case less than len bytes are
read undef is returned.

=cut
sub read_telescope($$) {
	my ($port,$len) = @_;
	my $response;
	my $char;
	my $count;
	my $total=0;
	do {
		($count,$char)=$port->read(1);
		if ($count == 0) { return undef; }
		$total += $count;
		$response .= $char;
	} while ($total < $len);

	# if the last byte is not '#', this means that the device did
	# not respond and the next byte should be '#' (hopefully)
	if ($char ne "#") {
		($count,$char)=$port->read(1);
		return undef;
	}
	return $response;
}

=item write_telescope(port, data)

Writes data to the telescope and the result of write is returned.

=cut
sub write_telescope($$) {
	my ($port, $data) = @_;

	return $port->write($data);
}

=item close_telescope_port(port)

Closes the communication port to the telescope.

=cut

sub close_telescope_port($) {
	my ($port) = @_;

	$port->close;
  	undef $port;
}

#
#  Telescope Commands
#

=back

=head1 TELESCOPE COMMANDS

=over 8

=item tc_check_align(port)

If the telescope is aligned 1 is returned else 0 is returned. If no response received,
undef is returned.

=cut
sub tc_check_align($) {
	my ($port) = @_;

	$port->write("J");
	my $response = read_telescope($port,2);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item tc_goto_rade(port, ra, de)

=item tc_goto_rade_p(port, ra, de)

Slew the telescope to RA/DEC coordinates ra, de (in decimal degrees).
Function tc_goto_rade_p uses precise GOTO.
If RA is not in [0;360] function returns -1. If DEC is not in [-90;90] -2 is returned.
If no response received, undef is returned.

=cut
sub tc_goto_rade {
	my ($port, $ra, $de, $precise) = @_;
	if (($ra < -0.1) or ($ra > 360.1)) {
		return -1;
	}
	if (($de < -90.1) or ($de > 90.1)) {
		return -2;
	}
	my $nex;
	if((defined $precise) and ($precise =! 0)) {
		$nex=dd2pnex($ra, $de);
		$port->write("r".$nex);
	} else {
		$nex=dd2nex($ra, $de);
		$port->write("R".$nex);
	}
	my $response = read_telescope($port,1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

sub tc_goto_rade_p {
	return tc_goto_rade(@_, 1);
}

=item tc_goto_azalt(port, az, alt)

=item tc_goto_azalt_p(port, az, alt)

Slew the telescope to AZ/ALT coordinates az, alt (in decimal degrees). Function tc_goto_azalt_p uses precise GOTO.
If AZ is not in [0;360] function returns -1. If ALT is not in [-90;90] -2 is returned.
If no response received, undef is returned.

=cut
sub tc_goto_azalt {
	my ($port, $az, $alt, $precise) = @_;
	if (($az < -0.1) or ($az > 360.1)) {
		return -1;
	}
	if (($alt < -90.1) or ($alt > 90.1)) {
		return -2;
	}
	my $nex;
	if((defined $precise) and ($precise =! 0)) {
		$nex=dd2pnex($az, $alt);
		$port->write("b".$nex);
	} else {
		$nex=dd2nex($az, $alt);
		$port->write("B".$nex);
	}
	my $response = read_telescope($port,1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

sub tc_goto_azalt_p {
	return tc_goto_azalt(@_, 1);
}

=item tc_get_rade(port)

=item tc_get_rade_p(port)

Returns the the current telescope RA/DEC coordinates ra, de (in decimal degrees). Function
tc_get_rade_p uses precise GET. If no response received, undef is returned.

=cut
sub tc_get_rade {
	my ($port, $precise) = @_;

	my $ra;
	my $de;

	if((defined $precise) and ($precise =! 0)) {
		$port->write("e");
		my $response = read_telescope($port, 18);
		if (! defined $response) {
			return undef;
		}
		($ra,$de) = pnex2dd($response);
	} else {
		$port->write("E");
		my $response = read_telescope($port, 10);
		if (! defined $response) {
			return undef;
		}
		($ra,$de) = nex2dd($response);
	}

	return ($ra, $de);
}

sub tc_get_rade_p {
	return tc_get_rade(@_, 1);
}

=item tc_get_azalt(port)

=item tc_get_azalt_p(port)

Returns the the currents telescope AZ/ALT coordinates az, alt (in decimal degrees). Function
tc_get_azalt_p uses precise GET. If no response received, undef is returned.

=cut
sub tc_get_azalt {
	my ($port, $precise) = @_;

	my $az;
	my $alt;

	if((defined $precise) and ($precise =! 0)) {
		$port->write("z");
		my $response = read_telescope($port, 18);
		if (! defined $response) {
			return undef;
		}
		($az,$alt) = pnex2dd($response);
	} else {
		$port->write("Z");
		my $response = read_telescope($port, 10);
		if (! defined $response) {
			return undef;
		}
		($az,$alt) = nex2dd($response);
	}

	return ($az, $alt);
}

sub tc_get_azalt_p {
	return tc_get_azalt(@_, 1);
}

=item tc_sync_rade(port, ra, de)

=item tc_sync_rade_p(port, ra, de)

Syncs the telescope to RA/DEC coordinates ra, de (in decimal degrees). Function tc_goto_azalt_p uses precise sync.
If RA is not in [0;360] function returns -1. If DEC is not in [-90;90] -2 is returned.
If no response received, undef is returned.

=cut
sub tc_sync_rade {
	my ($port, $ra, $de, $precise) = @_;
	if (($ra < 0) or ($ra > 360)) {
		return -1;
	}
	if (($de < -90) or ($de > 90)) {
		return -2;
	}
	my $nex;
	if((defined $precise) and ($precise =! 0)) {
		$nex=dd2pnex($ra, $de);
		$port->write("s".$nex);
	} else {
		$nex=dd2nex($ra, $de);
		$port->write("S".$nex);
	}
	my $response = read_telescope($port, 1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

sub tc_sync_rade_p {
	return tc_sync_rade(@_, 1);
}

=item tc_goto_in_progress(port)

Returns 1 if GOTO is in progress else 0 is returned. If no response received, undef is returned.

=cut
sub tc_goto_in_progress($) {
	my ($port) = @_;

	$port->write("L");
	my $response = read_telescope($port, 2);
	if (defined $response) {
		return substr($response, 0, 1);
	} else {
		return undef;
	}
}

=item tc_goto_cancel(port)

Cancels the GOTO operation. On success 1 is returned. If no response received, undef is returned.

=cut
sub tc_goto_cancel($) {
	my ($port) = @_;

	$port->write("M");
	my $response = read_telescope($port, 1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_echo(port, char)

Checks the communication with the telescope. This function sends char to the telescope and
returns the echo received. If no response received, undef is returned.

=cut
sub tc_echo($$) {
	my ($port, $char) = @_;

	$port->write("K".substr($char, 0, 1));
	my $response = read_telescope($port, 2);
	if (defined $response) {
		return substr($response, 0, 1);
	} else {
		return undef;
	}
}

=item tc_get_model(port)

This function returns the mount model as a number. See CELESTRON documentation.
If no response received, undef is returned.

=cut
sub tc_get_model($) {
	my ($port) = @_;

	$port->write("m");
	my $response = read_telescope($port, 2);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item tc_get_version(port)

This function returns the mount version as a number. See CELESTRON documentation.
If no response received, undef is returned.

=cut
sub tc_get_version($) {
	my ($port) = @_;

	$port->write("V");
	my $response = read_telescope($port, 3);
	if (defined $response) {
		return ord(substr($response, 0, 1)).
			   ".".ord(substr($response, 1, 1));
	} else {
		return undef;
	}
}


=item tc_get_location(port)

This function returns the stored location coordinates lon, lat in decimal degrees.
Negative longitude is WEST. Negative latitude is SOUTH.
If no response received, undef is returned.

=item tc_get_location_str(port)

This function returns the stored location coordinates lon and lat as strings.
If no response received, undef is returned.

=cut
sub tc_get_location {
	my ($port,$str) = @_;

	$port->write("w");
	my $response = read_telescope($port, 9);
	if (! defined $response) {
		return undef;
	}

	my $latd=ord(substr($response, 0, 1));
	my $latm=ord(substr($response, 1, 1));
	my $lats=ord(substr($response, 2, 1));
	my $lato=ord(substr($response, 3, 1));
	my $lond=ord(substr($response, 4, 1));
	my $lonm=ord(substr($response, 5, 1));
	my $lons=ord(substr($response, 6, 1));
	my $lono=ord(substr($response, 7, 1));

	my $lon;
	my $lat;
	if((defined $str) and ($str =! 0)) {
		$lat=sprintf("%d %02d'%02d\"N",$latd,$latm,$lats);
		$lon=sprintf("%d %02d'%02d\"E",$lond,$lonm,$lons);
		if ($lato) {
			$lat =~ s/N$/S/;
		}
		if ($lono) {
			$lon =~ s/E$/W/;
		}
	} else {
		$lat=($latd + $latm/60.0 + $lats/3600.0);
		$lon=($lond + $lonm/60.0 + $lons/3600.0);
		if ($lato) {
			$lat *= -1;
		}
		if ($lono) {
			$lon *= -1;
		}
	}
	return ($lon, $lat);
}

sub tc_get_location_str {
	return tc_get_location(@_, 1);
}

=item tc_set_location(port,lon,lat)

This function sets the location coordinates lon, lat in decimal degrees.
Negative longitude is WEST. Negative latitude is SOUTH.
If the coordinates are invalid -1 is returned.
If no response received, undef is returned.

=cut
sub tc_set_location {
	my ($port,$lon,$lat) = @_;
	my $issouth = 0;
	my $iswest = 0;

	if ($lon < 0) {
		$lon *= -1;
		$issouth = 1;
	}
	if ($lat < 0) {
		$lat *= -1;
		$iswest = 1;
	}

	if (($lat > 90) or ($lon > 180)) {
		return -1;
	}

	my ($lond,$lonm,$lons) = d2dms2($lon);
	my ($latd,$latm,$lats) = d2dms2($lat);

	$port->write("W");
	$port->write(chr($latd));
	$port->write(chr($latm));
	$port->write(chr($lats));
	$port->write(chr($issouth));
	$port->write(chr($lond));
	$port->write(chr($lonm));
	$port->write(chr($lons));
	$port->write(chr($iswest));

	my $response = read_telescope($port, 1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_get_time(port)

This function returns the stored time (in unixtime format), timezone (in hours) and daylight saving time(0|1).
If no response received, undef is returned.

=item tc_get_time_str(port)

This function returns the stored date, time (as strings), timezone (in hours) and daylight saving time(0|1).
If no response received, undef is returned.

=cut

sub tc_get_time {
	my ($port,$str) = @_;

	$port->write("h");
	my $response = read_telescope($port, 9);
	if (! defined $response) {
		return undef;
	}

	my $h=ord(substr($response, 0, 1));
	my $m=ord(substr($response, 1, 1));
	my $s=ord(substr($response, 2, 1));
	my $mon=ord(substr($response, 3, 1));
	my $day=ord(substr($response, 4, 1));
	my $year=ord(substr($response, 5, 1))+2000;
	my $tz=ord(substr($response, 6, 1));
	$tz -= 256 if ($tz > 12);
	my $dst=ord(substr($response, 7, 1));

	if((defined $str) and ($str =! 0)) {
		my $time=sprintf("%2d:%02d:%02d",$h,$m,$s);
		my $date=sprintf("%02d-%02d-%04d",$day,$mon,$year);
		return ($date,$time, $tz, $dst);
	} else {
		my $time = timelocal($s,$m,$h,$day,$mon-1,$year);
		return ($time, $tz, $dst);
	}
}

sub tc_get_time_str {
	return tc_get_time(@_, 1);
}

=item tc_set_time(port, time, timezone, daylightsaving)

This function sets the time (in unix time format), timezone (in hours) and daylight saving time(0|1).
On success 1 is returned.
If no response received, undef is returned. If the mount is known to have RTC
(currently only CGE and AdvancedVX) the date/time is set to RTC too.

=cut
sub tc_set_time {
	my ($port, $time, $tz, $dst) = @_;

	my $timezone = $tz;
	$tz += 256 if ($tz < 0);

	if ((defined $dst) and ($dst != 0)) {
		$dst=1;
	} else {
		$dst=0;
	}

	my ($s,$m,$h,$day,$mon,$year,$wday,$yday,$isdst) = localtime($time);

	$port->write("H");
	$port->write(chr($h));
	$port->write(chr($m));
	$port->write(chr($s));
	$port->write(chr($mon+1));
	$port->write(chr($day));
	# $year is actual_year-1900
	# here is required actual_year-2000
	# so we need $year-100
	$port->write(chr($year-100));
	$port->write(chr($tz));
	$port->write(chr($dst));

	my $response = read_telescope($port, 1);
	if (! defined $response) {
		return undef;
	}

	my $model = tc_get_model($port);
	# If the mount has RTC set date/time to RTC too
	# I only know CGE(5) and AdvancedVX(20) to have RTC
	if (($model == 5) or ($model == 20)) {
		# RTC expects UT, convert localtime to UT
		my ($s,$m,$h,$day,$mon,$year,$wday,$yday,$isdst) = localtime($time - (($timezone + $dst) * 3600));

		# Set year
		my $response = tc_pass_through_cmd($port, 3, 178, 132,
		                                   int(($year + 1900) / 256),
		                                   int(($year + 1900) % 256), 0, 0);
		if (! defined $response) {
			return undef;
		}

		# Set month and day
		my $response = tc_pass_through_cmd($port, 3, 178, 131, $mon+1, $day, 0, 0);
		if (! defined $response) {
			return undef;
		}

		# Set time
		my $response = tc_pass_through_cmd($port, 4, 178, 179, $h, $m, $s, 0);
		if (! defined $response) {
			return undef;
		}
	}
	return 1;
}

=item tc_get_tracking_mode(port)

Reads the tracking mode of the mount and returns one of the folowing:
TC_TRACK_OFF, TC_TRACK_ALT_AZ, TC_TRACK_EQ_NORTH, TC_REACK_EQ_SOUTH.
If no response received, undef is returned.

=cut
sub tc_get_tracking_mode($) {
	my ($port) = @_;

	$port->write("t");
	my $response = read_telescope($port, 2);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item tc_set_tracking_mode(port, mode)

Sets the tracking mode of the mount to one of the folowing:
TC_TRACK_OFF, TC_TRACK_ALT_AZ, TC_TRACK_EQ_NORTH, TC_REACK_EQ_SOUTH.
If the mode is not one of the listed -1 is returned.
If no response received, undef is returned.

=cut
sub tc_set_tracking_mode($$) {
	my ($port,$mode) = @_;

	if (($mode < 0) or ($mode > 3)) {
		return -1;
	}
	$port->write("T");
	$port->write(chr($mode));
	my $response = read_telescope($port, 1);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_slew_fixed(port, axis, direction, rate)

Move the telescope the telescope around a specified axis in a given direction with fixed rate.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT. Direction can accept values
TC_DIR_POSITIVE and TC_DIR_NEGATIVE. Rate is from 0 to 9. Where 0 stops slewing and 9 is
the fastest speed.

On success 1 is returned. If rate is out of range -1 is returned.
If no response received, undef is returned.

=cut
sub tc_slew_fixed {
	my ($port,$axis,$direction,$rate) = @_;

	if ($axis>0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	if ($direction > 0) {
		$direction = _TC_DIR_POSITIVE + 30;
	} else {
		$direction = _TC_DIR_NEGATIVE + 30;
	}

	if (($rate < 0) or ($rate > 9)) {
		return -1;
	}
	$rate = int($rate);

	my $response = tc_pass_through_cmd($port, 2, $axis, $direction, $rate, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_slew_variable(port, axis, direction, rate)

Move the telescope the telescope around a specified axis in a given direction with specified rate.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT. Direction can accept values
TC_DIR_POSITIVE and TC_DIR_NEGATIVE. Rate is the speed in arcsec/sec. For example 3600
represents 1degree/sec.

On success 1 is returned. If no response received, undef is returned.

=cut
sub tc_slew_variable {
	my ($port,$axis,$direction,$rate) = @_;

	if ($axis>0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	if ($direction > 0) {
		$direction = _TC_DIR_POSITIVE;
	} else {
		$direction = _TC_DIR_NEGATIVE;
	}

	$rate = int(4*$rate);
	my $rateH = int($rate / 256);
	my $rateL = $rate % 256;
	#print "RATEf : $rateH $rateL\n";

	my $response = tc_pass_through_cmd($port, 3, $axis, $direction, $rateH, $rateL, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item get_model_name(model_id)

Return the name of the mount by the id from tc_get_model().
If the mount is not known undef is returned.

=cut

sub get_model_name($) {
	my ($model_id) = @_;
	return $mounts{$model_id};
}

=back

=head1 AUX COMMANDS

The following commands are not officially documented by Celestron. Please note that these
commands are reverse engineered and may not work exactly as expected.

=over 8

=item tc_get_autoguide_rate(port, axis)

Get autoguide rate for the given axis in percents of the sidereal rate.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT.

On success current value of autoguide rate is returned in the range [0-99].
If no response received, undef is returned.
=cut
sub tc_get_autoguide_rate($$) {
	my ($port,$axis) = @_;

	if ($axis > 0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	# Get autoguide rate (0x47)
	my $response = tc_pass_through_cmd($port, 1, $axis, 0x47, 0, 0, 0, 1);
	if (defined $response) {
		my $rate = ord(substr($response, 0, 1));
		return int(100 * $rate / 256);
	} else {
		return undef;
	}
}

=item tc_set_autoguide_rate(port, axis, rate)

Set autoguide rate for the given axis in percents of the sidereal rate.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT.
Rate must be in the range [0-99].

On success 1 is returned. If rate is out of range -1 is returned.
If no response received, undef is returned.
=cut
sub tc_set_autoguide_rate($$$) {
	my ($port,$axis,$rate) = @_;

	if ($axis > 0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	# $rate should be [0%-99%]
	my $rate = int($rate);
	if (($rate < 0) or ($rate > 99)) {
		return -1;
	}

	# This is wired, but is done to match as good as
	# possible the values given by the HC
	my$rrate;
	if ($rate == 0) {
		$rrate = 0;
	} elsif ($rate == 99) {
		$rrate = 255;
	} else {
		$rrate = int((256 * $rate / 100) + 1);
	}

	# Set autoguide rate (0x46)
	my $response = tc_pass_through_cmd($port, 2, $axis, 0x46, $rrate, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_get_backlash(port, axis, direction)

Get anti-backlash values for the specified axis in a given direction.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT. Direction
can accept values TC_DIR_POSITIVE and TC_DIR_NEGATIVE.

On success current value of backlash is returned in the range [0-99].
If no response received, undef is returned.
=cut
sub tc_get_backlash($$$) {
	my ($port,$axis,$direction) = @_;

	if ($axis > 0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	if ($direction > 0) {
		$direction = 0x40; # Get positive backlash
	} else {
		$direction = 0x41; # Get negative backlash
	}

	my $response = tc_pass_through_cmd($port, 1, $axis, $direction, 0, 0, 0, 1);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item tc_set_backlash(port, axis, direction, backlash)

Set anti-backlash values for the specified axis in a given direction.

Accepted values for axis are TC_AXIS_RA_AZM and TC_AXIS_DE_ALT. Direction can accept
values TC_DIR_POSITIVE and TC_DIR_NEGATIVE. Backlash must be in the range [0-99].

On success 1 is returned. If backlash is out of range -1 is returned.
If no response received, undef is returned.
=cut
sub tc_set_backlash($$$$) {
	my ($port,$axis,$direction,$backlash) = @_;

	if ($axis > 0) {
		$axis = _TC_AXIS_RA_AZM;
	} else {
		$axis = _TC_AXIS_DE_ALT;
	}

	if ($direction > 0) {
		$direction = 0x10; # Set positive backlash
	} else {
		$direction = 0x11; # Set negative backlash
	}

	my $backlash = int($backlash);
	if (($backlash < 0) or ($backlash > 99)) {
		return -1;
	}

	my $response = tc_pass_through_cmd($port, 2, $axis, $direction, $backlash, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item tc_pass_through_cmd(port, msg_len, dest_id, cmd_id, data1, data2, data3, res_len)

Send a pass through command to a specific device. This function is meant for an internal
library use and should not be used, unless you know exactly what you are doing.
Calling this function with wrong parameters can be dangerous and can break the telescope!

=cut
sub tc_pass_through_cmd($$$$$$$$) {
	my ($port, $msg_len, $dest_id, $cmd_id, $data1, $data2, $data3, $res_len) = @_;

	$port->write("P");
	$port->write(pack("c", $msg_len));
	$port->write(pack("c", $dest_id));
	$port->write(pack("c", $cmd_id));
	$port->write(pack("c", $data1));
	$port->write(pack("c", $data2));
	$port->write(pack("c", $data3));
	$port->write(pack("c", $res_len));

	# we should read $res_len + 1 byes to accomodate '#' at the end
	return read_telescope($port, $res_len + 1);
}

=back

=head1 PERIODIC ERROR CORRECTION FUNCTIONS

The following commands are not officially documented by Celestron. Please note that these
commands are reverse engineered and may not work exactly as expected.

=over 8

=item pec_index_found(port)

Determine if the position index is found and the mount will know from where to start
PEC data playback.

If the index is found 1 is returned. If it is not found 0 is returned. In case of an error
the function returs undef.

=cut

sub pec_index_found($) {
	my ($port) = @_;

	my $response = tc_pass_through_cmd($port, 1, _TC_AXIS_RA_AZM, 0x18, 0, 0, 0, 1);
	if (defined $response) {
		if (ord(substr($response, 0, 1))) {
			return 1;
		} else {
			return 0;
		}
	} else {
		return undef;
	}
}

=item pec_seek_index(port)

This command will move the mount slightly until the position index is found, so that the PEC
playback can be started from the correct position. The telescope will not return to the
original position when the index is found. The completion of the operation can be checked with
pec_index_found().

On success 1 is returned. In case of an error undef is returned.

=cut

sub pec_seek_index($) {
	my ($port) = @_;

	my $response = tc_pass_through_cmd($port, 1, _TC_AXIS_RA_AZM, 0x19, 0, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item pec_record(port, action)

Start or stop the recording of periodic error correction data. The action parameter can
be PEC_START or PEC_STOP to start or stop the recording. The completion of the recording
can be monitored with pec_record_complete(). The data is collected by the mount from the
user or auto-guider corrections made during the recording process. This recording can take
10-15 minutes depending on the type of the mount.

On success 1 is returned. If a wrong parameter is provided -1 is returned. In case of an
error undef is returned.

=cut

sub pec_record($$) {
	my ($port,$action) = @_;
	my $cmd_id;

	if ($action == PEC_START) {
		$cmd_id = 0x0C;  # Start PEC record
	} elsif ($action == PEC_STOP){
		$cmd_id = 0x16;  # Stop PEC record
	} else {
		return -1;
	}

	my $response = tc_pass_through_cmd($port, 1, _TC_AXIS_RA_AZM, $cmd_id, 0, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item pec_record_complete(port)

Check the completion of pec_record().

If recording is complete 1 is returned. If recording is still in progress 0 is returned.
In case of an error undef is returned.

=cut

sub pec_record_complete($) {
	my ($port) = @_;

	my $response = tc_pass_through_cmd($port, 1, _TC_AXIS_RA_AZM, 0x15, 0, 0, 0, 1);
	if (defined $response) {
		if (ord(substr($response, 0, 1))) {
			return 1;
		} else {
			return 0;
		}
	} else {
		return undef;
	}
}

=item pec_playback(port, action)

Start or stop PEC playback. The action parameter can be PEC_START or PEC_STOP
to start or stop PEC playback respectively.

On success 1 is returned. If a wrong parameter is provided -1 is returned. In case of an
error undef is returned.

=cut

sub pec_playback($$) {
	my ($port,$action) = @_;

	if (($action != PEC_START) and ($action != PEC_STOP)) {
		return -1;
	}

	my $response = tc_pass_through_cmd($port, 2, _TC_AXIS_RA_AZM, 0x0d, $action, 0, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

=item pec_get_playback_index(port)

Get the index of the PEC data for the curent mount position in the range form 0 to
the value returned by pec_get_data_len() minus 1.

If the index position is not found yet, the function will always return 0.
On error undef is returned.

=cut

sub pec_get_playback_index($) {
	my ($port) = @_;

	my $response = tc_pass_through_cmd($port, 1, _TC_AXIS_RA_AZM, 0x0e, 0, 0, 0, 1);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item pec_get_data_len(port)

Get the length of the internal register array in which the PEC data is stored.

On error undef is returned.

=cut

sub pec_get_data_len($) {
	my ($port) = @_;

	my $response = tc_pass_through_cmd($port, 2, _TC_AXIS_RA_AZM, 0x30, 0x3f, 0, 0, 1);
	if (defined $response) {
		return ord(substr($response, 0, 1));
	} else {
		return undef;
	}
}

sub _pec_set_data($$$) {
	my ($port, $index, $data) = @_;

	my $response = tc_pass_through_cmd($port, 4, _TC_AXIS_RA_AZM, 0x31, 0x40+$index, $data, 0, 0);
	if (defined $response) {
		return 1;
	} else {
		return undef;
	}
}

sub _pec_get_data($$) {
	my ($port, $index) = @_;

	my $response = tc_pass_through_cmd($port, 2, _TC_AXIS_RA_AZM, 0x30, 0x40+$index, 0, 0, 1);
	if (defined $response) {
		return unpack("c", substr($response, 0, 1));
	} else {
		return undef;
	}
}

=item pec_set_data(port, data)

Upload the periodic error correction data to the mount. The data parameter is a reference to an
array with size that matches the value returned by pec_get_data_len(). The values must be in
arc seconds.

On success 1 is returned. If the size of the data array does not match the mount data size -1
is returned. If any of the PEC values is too big and can not fit in the internal data format -2 is returned.
On other error undef is returned.

=cut

sub pec_set_data($$) {
	my ($port, $data) = @_;
	my $res;

	my $len = pec_get_data_len($port);
	if (!defined $len) {
		return undef;
	}

	if ($len != @{$data}) {
		return -1;
	}

	my $index = 0;
	my $current = 0;
	foreach my $val (@{$data}) {
		my $diff = $val - $current;

		# I have no idea why the values are different for positive and negative numbers
		# I thought the coefficient should be 0.0772 arcsec/unit as the resolution of
		# 24bit number for 360 degrees. I tried to mach as best as I could the values
		# returned by Celestron's PECTool and I came up with this numbers...
		my $rdiff;
		if ($diff < 0) {
			$rdiff = sprintf("%.0f", $val / 0.0845) - sprintf("%.0f", $current / 0.0845);
		} else {
			$rdiff = sprintf("%.0f", $val / 0.0774) - sprintf("%.0f", $current / 0.0774);
		}
		if (($rdiff > 127) or ($rdiff < -127)) {
			return -2;
		}

		# print "$index => $rdiff\t(diff = $diff, val = $val)\n";
		$res = _pec_set_data($port, $index, $rdiff);
		if (!defined ($res)) {
			return undef;
		}
		$index++;
		$current = $val;
	}

	$res = pec_record($port, PEC_STOP);
	if (!defined ($res)) {
		return undef;
	}
	return 1;
}

=item pec_get_data(port)

Download the periodic error correction data from the mount. An array with the correction values is
returned. The size of the array is equal to the value returned by pec_get_data_len(). The values
are in arc seconds.

On error undef is returned.

=cut

sub pec_get_data($) {
	my ($port) = @_;
	my @data;

	my $len = pec_get_data_len($port);
	# my $len = 11;
	if (!defined $len) {
		return undef;
	}

	my $current = 0;
	for (my $index = 0; $index < $len; $index++) {
		my $rdiff = _pec_get_data($port, $index);
		# my $rdiff = $b[$index];
		if (!defined ($rdiff)) {
			return undef;
		}

		# I have no idea why the values are different for positive and negative numbers.
		# Pease se the note in pec_set_data()!
		if ($rdiff > 0) {
			$current += $rdiff * 0.0774;
		} else {
			$current += $rdiff * 0.0845;
		}
		$data[$index] = $current;
		# print "$index => $current\n";
	}
	return @data;
}

=back

=head1 UTILITY FUNCTIONS

=over 8

=item notnum(n)

If "n" is a real number returns 0 else it returns 1.

=cut
sub notnum($)
{	my ($num) = @_;
	if ($num=~ /^[-+]?\d+\.?\d*$/) {return 0;}
	else {return 1;}
}


=item precess(ra0, dec0, equinox0, equinox1)

Precesses coordinates ra0 and dec0 from equinox0 to equinox1 and returns the caclculated ra1 and dec1.
Where ra and dec should be in decimal degrees and equinox should be in years (and fraction of the year).

=cut
sub precess(@)
{
	my ($ra0,$de0,$eq0,$eq1)=@_;
	my ($cosd,$ra,$dec,
			$A,$B,$C,
			$x0,$y0,$z0,
			$x1,$y1,$z1,
			$ST,$T,$sec2rad);
	my @rot;

	my ($sinA,$sinB,$sinC,$cosA,$cosB,$cosC,$sind);

	my ($ra1,$de1);

	$ra = $ra0*DEG2RAD;
	$dec = $de0*DEG2RAD;

	$cosd = cos($dec);

	$x0=$cosd*cos($ra);
	$y0=$cosd*sin($ra);
	$z0=sin($dec);

	$ST=($eq0-2000.0)*0.001;
	$T=($eq1-$eq0)*0.001;

	$sec2rad=(DEG2RAD)/3600.0;
	$A=$sec2rad*$T*(23062.181+$ST*(139.656+0.0139*$ST)+$T*
                                (30.188-0.344*$ST+17.998*$T));
	$B=$sec2rad*$T*$T*(79.280+0.410*$ST+0.205*$T)+$A;
	$C=$sec2rad*$T*(20043.109-$ST*(85.33+0.217*$ST)+$T*
                                (-42.665-0.217*$ST-41.833*$T));

	$sinA=sin($A);  $sinB=sin($B);  $sinC=sin($C);
	$cosA=cos($A);  $cosB=cos($B);  $cosC=cos($C);

	$rot[0][0]=$cosA*$cosB*$cosC-$sinA*$sinB;
	$rot[0][1]=(-1)*$sinA*$cosB*$cosC-$cosA*$sinB;
	$rot[0][2]=(-1)*$sinC*$cosB;

	$rot[1][0]=$cosA*$cosC*$sinB+$sinA*$cosB;
	$rot[1][1]=(-1)*$sinA*$cosC*$sinB+$cosA*$cosB;
	$rot[1][2]=(-1)*$sinB*$sinC;

	$rot[2][0]=$cosA*$sinC;
	$rot[2][1]=(-1)*$sinA*$sinC;
	$rot[2][2]=$cosC;

	$x1=$rot[0][0]*$x0+$rot[0][1]*$y0+$rot[0][2]*$z0;
	$y1=$rot[1][0]*$x0+$rot[1][1]*$y0+$rot[1][2]*$z0;
	$z1=$rot[2][0]*$x0+$rot[2][1]*$y0+$rot[2][2]*$z0;

	if ($x1==0) {
		if ($y1 > 0) { $ra1=90.0;}
		else { $ra1=270.0;}
	}
	else {$ra1=atan2($y1,$x1)*RAD2DEG;}
	if($ra1<0) { $ra1+=360;}

	$de1=RAD2DEG*atan2($z1,sqrt(1-$z1*$z1));

	return ($ra1,$de1);
}

########################################################
######## Mathematics
########################################################

=item round(n)

Returns the rounded number n.

=cut
sub round($){
	my($num)=@_;
	my ($retval);
	if (($num - floor($num)) < 0.5) { $retval = floor($num); }
	else { $retval = floor($num) + 1; }
	return $retval;
}


=item d2hms(deg)

Converts deg (in decimal degrees) to string in hours, minutes and seconds notion (like "12h 10m 44s").

=cut
sub d2hms($)   # Looks OK! :)
{
	my ($ra)=@_;

	$ra=$ra/15;
	my $hr=int($ra*3600+0.5);
	my $hour=int($hr/3600);
	my $f=int($hr%3600);
	my $min=int($f/60);
	my $sec=int($f%60);
	my $ra_str = sprintf "%02dh %02dm %02ds", $hour,$min,$sec;
	return $ra_str;
}

=item d2dms(deg)

Converts deg (in decimal degrees) to string in degrees, minutes and seconds notion
(like "33:20:44").

=cut
sub d2dms($)  # Looks OK! :)
{
	my ($ang)=@_;
	if ($ang >= 0) {
		my $a=int($ang*3600+0.5);
		my $deg=int($a/3600);
		my $f=int($a%3600);
		my $min=int($f/60);
		my $sec=int($f%60);
		my $ang_str=sprintf "%02d:%02d:%02d",$deg,$min,$sec;
		return $ang_str;
	} else {
		$ang*=-1;
		my $a=int($ang*3600+0.5);
		my $deg=int($a/3600);
		my $f=int($a%3600);
		my $min=int($f/60);
		my $sec=int($f%60);
		my $ang_str=sprintf "-%02d:%02d:%02d",$deg,$min,$sec;
		return $ang_str;
	}
}

sub d2dms2($) {
	my ($ang)=@_;
	if ($ang >= 0) {
		my $a=int($ang*3600+0.5);
		my $deg=int($a/3600);
		my $f=int($a%3600);
		my $min=int($f/60);
		my $sec=int($f%60);
		return ($deg,$min,$sec);
	} else {
		$ang*=-1;
		my $a=int($ang*3600+0.5);
		my $deg=int($a/3600);
		my $f=int($a%3600);
		my $min=int($f/60);
		my $sec=int($f%60);
		return (-1*$deg,$min,$sec);
	}
}

=item d2dms(deg)

converts deg (in decimal degrees) to string in degrees and minutes notion (like "33:20").

=cut
sub d2dm($)
{
	my ($ang)=@_;
	my $a=int($ang*3600+0.5);
	my $deg=int($a/3600);
	my $f=int($a%3600);
	my $min=int($f/60);
	my $ang_str=sprintf "%02d:%02d",$deg,$min;
	return $ang_str;
}

=item dms2d(string)

converts string of the format "dd:mm:ss" to decimal degrees. If the string format
is invalid format, undef is returned.

=cut
sub dms2d($)
{
	my ($angle)=@_;

	my (@dms)=split(/:/,$angle);
	if (@dms>3 or $angle eq "") {
		return undef;
	}

	if (!($dms[0]=~ /^[+-]?\d+$/)) {
		 return undef;
	}
	if ($dms[1]<0 or $dms[1]>59 or $dms[1]=~/[\D]/) {
		return undef;
	}
	if ($dms[2]<0 or $dms[2]>59 or $dms[2]=~/[\D]/) {
		return undef;
	}

	if ($dms[0]=~ /^-/) {
		return ($dms[0]-$dms[1]/60-$dms[2]/3600);
	} else {
		return ($dms[0]+$dms[1]/60+$dms[2]/3600);
	}
}

=item hms2d(string)

Converts string of the format "hh:mm:ss" to decimal degrees. If the string format
is invalid format, undef is returned.

=cut
sub hms2d($)
{
	my ($hours)=@_;

	my (@hms)=split(/:/,$hours);
	if (@hms>3 or $hours eq "") {
		return undef;
	}

	if ($hms[0]<0 or $hms[0]>23 or $hms[0]=~/[\D]/) {
		return undef;
	}
	if ($hms[1]<0 or $hms[1]>59 or $hms[1]=~/[\D]/) {
		return undef;
	}
	if ($hms[2]<0 or $hms[2]>59 or $hms[2]=~/[\D]/) {
		return undef;
	}

	return (($hms[0]+$hms[1]/60+$hms[2]/3600)*15);
}

###############################################
#  NexStar coordinate conversion
###############################################

=item nex2dd(string)

Converts NexStar hexadecimal coordinate string (in fraction of a revolution) of
the format "34AB,12CE" to two decimal degree coordinates.

=cut
sub nex2dd ($){
	my ($nexres) = @_;
	my $d1_factor = hex(substr($nexres, 0, 4)) / 65536;
	my $d2_factor = hex(substr($nexres, 5, 4)) / 65536;
	my $d1 = 360 * $d1_factor;
	my $d2 = 360 * $d2_factor;

	# bring $d2 in [-90,+90] range
	# use 90.00001 to fix some float errors
	# that lead +90 to be converted to -270
	$d2 = $d2 + 360 if ($d2 < -90.0002);
	$d2 = $d2 - 360 if ($d2 > 90.0002);

	return($d1, $d2);
}

=item pnex2dd(string)

Converts precision NexStar hexadecimal coordinate string (in fraction of a revolution)
of the format "12AB0500,40000500" to two decimal degree coordinates.

=cut
sub pnex2dd ($){
	my ($nexres) = @_;
	my $d1_factor = hex(substr($nexres, 0, 8)) / 0xffffffff;
	my $d2_factor = hex(substr($nexres, 9, 8)) / 0xffffffff;
	my $d1 = 360 * $d1_factor;
	my $d2 = 360 * $d2_factor;

	# bring $d2 in [-90,+90] range
	# use 90.00001 to fix some float errors
	# that lead +90 to be converted to -270
	$d2 = $d2 + 360 if ($d2 < -90.0002);
	$d2 = $d2 - 360 if ($d2 > 90.0002);

	return($d1, $d2);
}


=item dd2nex(deg1,deg2)

Converts coordinates deg1 and deg2 (in decimal degrees) to NexStar hexadecimal coordinate
string (in fraction of a revolution) of the format "34AB,12CE".

=cut
sub dd2nex ($$) {
	my ($d1, $d2) = @_;

	# bring $d1,$d2 in the range [0-360]
	$d1 = $d1 - 360 * int($d1/360);
	$d2 = $d2 - 360 * int($d2/360);
	$d1 = $d1 + 360 if ($d1 < 0);
	$d2 = $d2 + 360 if ($d2 < 0);

	my $d2_factor = $d2 / 360;
	my $d1_factor = $d1 / 360;

	my $nex1 = int($d1_factor*65536);
	my $nex2 = int($d2_factor*65536);

	return sprintf("%04X,%04X", $nex1,$nex2);
}

=item dd2nex(deg1,deg2)

Converts coordinates deg1 and deg2 (in decimal degrees) to precise NexStar hexadecimal
coordinate string (in fraction of a revolution) of the format "12AB0500,40000500".

=cut
sub dd2pnex ($$) {
	my ($d1, $d2) = @_;

	# bring $d1,$d2 in the range [0-360]
	$d1 = $d1 - 360 * int($d1/360);
	$d2 = $d2 - 360 * int($d2/360);
	$d1 = $d1 + 360 if ($d1 < 0);
	$d2 = $d2 + 360 if ($d2 < 0);

	my $d2_factor = $d2 / 360;
	my $d1_factor = $d1 / 360;

	my $nex1 = int($d1_factor*0xffffffff);
	my $nex2 = int($d2_factor*0xffffffff);

	return sprintf("%08X,%08X", $nex1,$nex2);
}

=back

=head1 SEE ALSO

For more information about the NexStar commands please refer to the original
protocol specification described here:
http://www.celestron.com/c3/images/files/downloads/1154108406_nexstarcommprot.pdf

Some of the undocumented commands are described here:
http://www.paquettefamily.ca/nexstar/NexStar_AUX_Commands_10.pdf

=head1 AUTHOR

Rumen Bogdanovski, [e-mail]

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2013-2014 by Rumen Bogdanovski

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.12.4 or,
at your option, any later version of Perl 5 you may have available.

The author assumes no liability or responsibility for damage or injury
to persons or property arising from any use of this product. Use it at
your own risk.

=cut

1;