Never been one to let the carrier drop

use Device::SerialPort;
use Data::Dumper;
use strict;

sub new {
my $self = {};
my $type = shift;
my $port = shift;

$self->{'debug'} = 0;
$self->{'port'} = $port;
$self->{'dev'} = Device::SerialPort->new($port, 1) || die "Failed to open $port";
$self->{'dev'}->baudrate(2400);
$self->{'dev'}->parity('none');
$self->{'dev'}->databits(8);
$self->{'dev'}->stopbits(1);
$self->{'dev'}->dtr_active(1);

$self->{'dev'}->debug($self->{'debug'}) if($self->{'debug'});
$self->{'dev'}->write_settings;
$self->{'dev'}->read_const_time(3000);
my $r = bless($self, $type);

return $r;
}

sub read {
my $self = shift;
$self->{'dev'}->reset_error;
my ($count,$buf) = $self->{'dev'}->read(64);
print "count: $count\n" if($self->{'debug'});
my @array = split(//,$buf);
my $notOk = 1;
while($notOk && @array) {
my $z = shift(@array);

print "z: " . ord($z) if($self->{'debug'});

my $checksum = (ord($z) & 0xF0) >> 4;
print "checksum: $checksum\n" if($self->{'debug'});
if($checksum == 1) {
unshift(@array,$z);
$notOk = 0;
}
}
my @v_array;
# first check high order bits
my ($i, $checksum);
for($i=0;$i<14;$i++) { $checksum = ord($array[$i]) & 0xF0; $v_array[$i] = ord($array[$i]) & 0x0F; $checksum = $checksum >> 4;
if($checksum != ($i+1)) {
print "Checksum mismatch at $i ($checksum)\n" if($self->{'debug'});
return undef;
}

}

# second decode reading;
my $mode;

$self->{'smode'} = "AC" if($v_array[0] & 8);
$self->{'smode'} = "DC" if($v_array[0] & 4);
# bit 2 is auto ranging, do we care?
# bit 1 is RS232, um, if you don't know that, what are you doing here?
$self->{'sign'} = "+";
$self->{'sign'} = "-" if($v_array[1] & 8);
$self->{'digit1'} = $self->convert_digit($v_array[1], $v_array[2], 0 );
$self->{'digit2'} = $self->convert_digit($v_array[3], $v_array[4], 1 );
$self->{'digit3'} = $self->convert_digit($v_array[5], $v_array[6], 1 );
$self->{'digit4'} = $self->convert_digit($v_array[7], $v_array[8], 1 );

$self->{'number'} = $self->{'sign'} . $self->{'digit1'} . $self->{'digit2'} . $self->{'digit3'} . $self->{'digit4'};

$self->{'range'} = 'u' if($v_array[9] & 8);
$self->{'number'} *= 0.000001 if($v_array[9] & 8);

$self->{'range'} = 'n' if($v_array[9] & 4);
$self->{'number'} *= 0.000000001 if($v_array[9] & 4);
$self->{'range'} = 'k' if($v_array[9] & 2);
$self->{'number'} *= 1000 if($v_array[9] & 2);

# 1 is diode, do we care?
$self->{'range'} = 'm' if($v_array[10] & 8);
$self->{'number'} *= 0.001 if($v_array[10] & 8);

$self->{'range'} = '%' if($v_array[10] & 4);
$self->{'range'} = 'M' if($v_array[10] & 2);
$self->{'number'} *= 1000000 if($v_array[10] & 2);

$self->{'mode'} = "farad" if($v_array[11] & 8);
$self->{'mode'} = "ohm" if($v_array[11] & 4);
$self->{'mode'} = "delta" if($v_array[11] & 2);

# bit 1 is hold, do we care?

$self->{'mode'} = "amps" if($v_array[12] & 8);
$self->{'mode'} = "volts" if($v_array[12] & 4);
$self->{'mode'} = "hz" if($v_array[12] & 2);

return $self->{'smode'} . ' ' . $self->{'mode'} . " " . $self->{'sign'} . " " . $self->{'digit1'} . $self->{'digit2'} . $self->{'digit3'} . $self->{'digit4'} . ' ' . $self->{'range'};

}

sub convert_digit {
my $self = shift;
my $lhs = shift;
my $rhs = shift;
my $include_decimal = shift;
my $decimal;

if($include_decimal) {
if($lhs & 8) {
$decimal = ".";
} else {
$decimal = "";
}
}

$lhs = $lhs & 7;

my $d;

# 000 0101 = 1
if($lhs == 0 && $rhs == 5) {
$d = 1;
# 101 1011 = 2
} elsif($lhs == 5 && $rhs == 11) {
$d = 2;
# 001 1111 = 3
} elsif($lhs == 1 && $rhs == 15) {
$d = 3;
# 010 0111 = 4
} elsif($lhs == 2 && $rhs == 7) {
$d = 4;
# 011 1110 = 5
} elsif($lhs == 3 && $rhs == 14) {
$d = 5;
# 111 1110 = 6
} elsif( $lhs == 7 && $rhs == 14) {
$d = 6;
# 001 0101 = 7
} elsif($lhs == 1 && $rhs == 5) {
$d = 7;
# 111 1111 = 8
} elsif($lhs == 7 && $rhs == 15) {
$d = 8;
# 011 1111 = 9
} elsif($lhs == 3 && $rhs == 15 ) {
$d = 9;
# 111 1101 = 0
} elsif($lhs == 7 && $rhs == 13 ) {
$d = 0;
} elsif($lhs == 6 && $rhs == 8) {
$d = "L";
} else {
return undef;
}

my $v = $decimal . $d;
print "V: $v\n" if($self->{'debug'});
return $v;
}