viewvc.cgi/RFID/3m-810.pl

#!/usr/bin/perl

use Device::SerialPort qw (:STAT);
use strict;
use warnings;

use Data::Dump qw/dump/;
use Carp qw/confess/;

my $debug = 0;

my $response = {
        'd500090400110a0500027250'                              => 'version?',
        'd60007fe00000500c97b'                                  => 'no tag in range',

        'd6000ffe00000501e00401003123aa26941a'  => 'tag #1',
        'd6000ffe00000501e0040100017c0c388e2b'  => 'rfid card',
        'd6000ffe00000501e00401003123aa2875d4'  => 'tag red-stripe',

        'd60017fe00000502e00401003123aa26e0040100017c0c38cadb' => 'tag #1 + card',
        'd60017fe00000502e00401003123aa26e00401003123aa283124' => 'tag #1 + tag red-stripe',
};

=head1 NAME

3m-810 - support for 3M 810 RFID reader

=head1 SYNOPSIS

3m-810.pl [DEVICE [BAUD [DATA [PARITY [STOP [FLOW]]]]]]

=head1 DESCRIPTION

Communicate with 3M 810 RFID reader and document it's protocol

=head1 SEE ALSO

L<Device::SerialPort(3)>

L<perl(1)>

L<http://stackoverflow.com/questions/149617/how-could-i-guess-a-checksum-algorithm>

=head1 AUTHOR

Dobrica Pavlinusic <dpavlin@rot13.org> L<http://www.rot13.org/~dpavlin/>

=head1 COPYRIGHT AND LICENSE

This program is free software; you may redistribute it and/or modify
it under the same terms ans Perl itself.

=cut

# your serial port.
my ($device,$baudrate,$databits,$parity,$stopbits,$handshake)=@ARGV;
$device    ||= "/dev/ttyUSB0";
$baudrate  ||= "19200";
$databits  ||= "8";
$parity    ||= "none";
$stopbits  ||= "1";
$handshake ||= "none";

my $port=new Device::SerialPort($device) || die "new($device): $!\n";
$handshake=$port->handshake($handshake);
$baudrate=$port->baudrate($baudrate);
$databits=$port->databits($databits);
$parity=$port->parity($parity);
$stopbits=$port->stopbits($stopbits);

print "## using $device $baudrate $databits $parity $stopbits\n";

# Just in case: reset our timing and buffers
$port->lookclear();
$port->read_const_time(100);
$port->read_char_time(5);

# Turn on parity checking:
#$port->stty_inpck(1);
#$port->stty_istrip(1);

# initial hand-shake with device

cmd( 'D5 00  05   04 00 11                 8C66', 'hw version?',
     'D5 00  09   04 00 11   0A 05 00 02   7250', 'hw 10.5.0.2', sub {
        print "hardware version ", join('.', unpack('CCCC', skip_assert(3) )), "\n";
});

cmd( 'D6 00  0C   13  04  01 00  02 00  03 00  04 00   AAF2','stats?',
     'D6 00  0C   13  00  02 01 01 03 02 02 03  00     E778','FIXME: unimplemented', sub { assert() }  );

# start scanning for tags

cmd( 'D6 00  05   FE     00  05         FA40', "XXX scan $_",
     'D6 00  07   FE  00 00  05     00  C97B', 'no tag', sub {
dispatch( 
         'D6 00  0F   FE  00 00  05 ',# 01 E00401003123AA26  941A        # seen, serial length: 8
                sub {
                        my $rest = shift || die "no rest?";
                        my $nr = ord( substr( $rest, 0, 1 ) );
                        my $tags = substr( $rest, 1 );

                        my $tl = length( $tags );
                        die "wrong length $tl for $nr tags: ",dump( $tags ) if $tl =! $nr * 8;

                        my @tags;
                        push @tags, uc(unpack('H16', substr($tags, $_ * 8, 8))) foreach ( 0 .. $nr - 1 );
                        warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags ) if $debug;
                        print "seen $nr tags: ", join(',', @tags ) , "\n";

                        # XXX read first tag
                        read_tag( @tags );

                }
) }

) foreach ( 1 .. 100 );

my $read_cached;

sub read_tag {
        my ( $tag ) = @_;

        print "read_tag $tag\n";
        return if $read_cached->{ $tag }++;

        cmd(    "D6 00  0D  02      $tag   00   03     1CC4", 'read offset: 0 blocks: 3' );

        #        D6 00  1F  02 00   $tag   03   00 00   04 11 00 01   01 00   30 30 30 30   02 00   30 30 30 30    E5F4
        warn "?? D6 00  1F  02 00   $tag   03   00 00   04 11 00 01   01 00   31 32 33 34   02 00   35 36 37 38    531F\n";
if (0) {
        cmd(    "D6 00  0D  02      $tag   03   04     3970", 'read offset: 3 blocks: 4' );

        #        D6 00  25  02 00   $tag   04                         03 00   30 30 00 00   04 00   00 00 00 00   
        #                           $tag                              05 00   00 00 00 00   06 00   00 00 00 00    B9BA
        warn "?? D6 00  25  02 00   $tag   04                         03 00   39 30 31 32   04 00   ....\n";
}
        warn "?? D6 00  0F  FE  00 00  05 01   $tag  941A ##### ready?\n";

}

for ( 1 .. 3 ) {

#                                                              ++-->type 00-0a
#     D6 00  2A  04     E00401003123AA26  00  07  00  04 11 00 01 31 31 31 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1C D4
#     D6 00 2A 04 E0 04 01 00 31 23 AA 26 00  07  00  04 11 00 06 32 32 32 32 32 32 32 32 32 32 32 00 00 00 00 00 00 00 00 00 00 00 00 00 32B7
#     D6 00 2A 04 E0 04 01 00 31 23 AA 26 00  07  00  04 11 00 02 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 00 00 00 00 00 00 00 00 42 1F

cmd(' D6 00  2A  04     E00401003123AA26  00  07  00  04 11 00 01 30 30 30 30 30 30 30 30 30 30 00 00 00 00 00 00 00 00 00 00 00 00 00 00   8843', "write offset 0, block: 7 -- 0000000000 $_" );
warn "D6 00  0D  04 00  E00401003123AA26  07  CFF1 -- ack 7 block?\n";

}
warn "  D6 00   0F   FE 00   00   05 01  E00401003123AA26 941A\n";

cmd( 'D6 00 05 FE 00 05 FA 40', "port-write scan $_" ) foreach ( 1 .. 2 );

cmd('D6 00  0C  09    E00401003123AA26  D7  3AF0', 'checkin?',
    'D6 00  0C  09 00 E00401003123AA26      6A44 -- no?' );
cmd('D6 00  0C  09    E00401003123AA26  DA  EB5D', 'checkout?',
    'D6 00  0C  09 00 E00401003123AA26      6A44 -- no?' );

cmd('D6 00  26  04    E00401003123AA26  00  06  00  55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55  A98B', 'blank offset: 0 blocks: 6', 
    'D6 00  0D  04 00 E00401003123AA26  06  DFD0 -- ack 6 blocks' ) foreach ( 1 .. 3 );

undef $port;
print "Port closed\n";

sub writechunk
{
        my $str=shift;
        my $count = $port->write($str);
        print "#> ", as_hex( $str ), "\t[$count]\n";
}

sub as_hex {
        my @out;
        foreach my $str ( @_ ) {
                my $hex = unpack( 'H*', $str );
                $hex =~ s/(..)/$1 /g if length( $str ) > 2;
                $hex =~ s/\s+$//;
                push @out, $hex;
        }
        return join(' | ', @out);
}

sub read_bytes {
        my ( $len, $desc ) = @_;
        my $data = '';
        while ( length( $data ) < $len ) {
                my ( $c, $b ) = $port->read(1);
                #warn "## got $c bytes: ", as_hex($b), "\n";
                $data .= $b;
        }
        $desc ||= '?';
        warn "#< ", as_hex($data), "\t$desc\n" if $debug;
        return $data;
}

our $assert;

# my $rest = skip_assert( 3 );
sub skip_assert {
        assert( 0, shift );
}

sub assert {
        my ( $from, $to ) = @_;

        $from ||= 0;
        $to = length( $assert->{expect} ) if ! defined $to;

        my $p = substr( $assert->{payload}, $from, $to );
        my $e = substr( $assert->{expect},  $from, $to );
        warn "EXPECTED ",as_hex($e), " GOT ", as_hex($p), " [$from-$to] in ",dump( $assert ), "\n" if $e ne $p;

        # return the rest
        return substr( $assert->{payload}, $to );
}

our $dispatch;
sub dispatch {
        my ( $pattern, $coderef ) = @_;
        my $patt = substr( str2bytes($pattern), 3 ); # just payload
        my $l = length($patt);
        my $p = substr( $assert->{payload}, 0, $l );
        warn "## dispatch pattern $pattern [$l] ",dump( $patt, $p ) if $debug;

        if ( $assert->{payload} eq $assert->{expect} ) {
                warn "## no dispatch, payload expected" if $debug;
        } elsif ( $p eq $patt ) {
                # if matched call with rest of payload
                $coderef->( substr( $assert->{payload}, $l ) );
        } else {
                warn "## dispatch ignored" if $debug;
        }
}

use Digest::CRC;

sub crcccitt {
        my $bytes = shift;
        my $crc = Digest::CRC->new(
                # midified CCITT to xor with 0xffff instead of 0x0000
                width => 16, init => 0xffff, xorout => 0xffff, refout => 0, poly => 0x1021, refin => 0,
        ) or die $!;
        $crc->add( $bytes );
        pack('n', $crc->digest);
}

# my $checksum = checksum( $bytes );
# my $checksum = checksum( $bytes, $original_checksum );
sub checksum {
        my ( $bytes, $checksum ) = @_;

        my $xor = crcccitt( substr($bytes,1) ); # skip D6
        warn "## checksum ",dump( $bytes, $xor, $checksum ) if $debug;

        my $len = ord(substr($bytes,2,1));
        my $len_real = length($bytes);
        print "length wrong: $len_real != $len\n" if $len_real != $len;

        if ( defined $checksum && $xor ne $checksum ) {
                print "checksum doesn't match: ", as_hex($xor), " != ", as_hex($checksum), " data: ", as_hex($bytes), "\n";
                return $bytes . $xor;
        }
        return $bytes . $checksum;
}

sub readchunk {
        my ( $parser ) = @_;

        sleep 1;        # FIXME remove

        # read header of packet
        my $header = read_bytes( 2, 'header' );
        my $length = read_bytes( 1, 'length' );
        my $len = ord($length);
        my $data = read_bytes( $len, 'data' );

        my $payload  = substr( $data, 0, -2 );
        my $payload_len = length($data);
        warn "## payload too short $payload_len != $len\n" if $payload_len != $len;

        my $checksum = substr( $data, -2, 2 );
        checksum( $header . $length . $payload, $checksum );

        print "<< ",as_hex( $header ), " [$len] ", as_hex( $payload ), " | sum: ",as_hex($checksum),"\n";

        $assert->{len}      = $len;
        $assert->{payload}  = $payload;

        $parser->( $len, $payload ) if $parser && ref($parser) eq 'CODE';

        return $data;
}

sub str2bytes {
        my $str = shift || confess "no str?";
        my $b = $str;
        $b =~ s/\s+(\S\S)(\S\S)+\s*/ $1 $2/;    # fix checksum
        $b =~ s/\s+$//;
        $b =~ s/\s+/\\x/g;
        $b = '"\x' . $b . '"';
        my $bytes = eval $b;
        die $@ if $@;
        warn "## str2bytes( $str ) => $b => ",as_hex($bytes) if $debug;
        return $bytes;
}

sub cmd {
        my ( $cmd, $cmd_desc, $expect, $expect_desc, $coderef ) = @_;
        my $bytes = str2bytes( $cmd );

        # fix checksum if needed
        $bytes = checksum( substr( $bytes, 0, -2 ), substr( $bytes, -2, 2 ) );

        warn ">> ", as_hex( $bytes ), "\t## $cmd_desc\n";
        $assert->{send} = $cmd;
        writechunk( $bytes );

        if ( $expect ) {
                warn "?? $expect", $expect_desc ? "\t## $expect_desc" : '', "\n";
                $assert->{expect} = substr(str2bytes($expect), 3, -2); # just expected payload
                readchunk( $coderef );
        }
}

1	#!/usr/bin/perl
2
3	use Device::SerialPort qw (:STAT);
4	use strict;
5	use warnings;
6
7	use Data::Dump qw/dump/;
8	use Carp qw/confess/;
9
10	my $debug = 0;
11
12	my $response = {
13	'd500090400110a0500027250' => 'version?',
14	'd60007fe00000500c97b' => 'no tag in range',
15
16	'd6000ffe00000501e00401003123aa26941a' => 'tag #1',
17	'd6000ffe00000501e0040100017c0c388e2b' => 'rfid card',
18	'd6000ffe00000501e00401003123aa2875d4' => 'tag red-stripe',
19
20	'd60017fe00000502e00401003123aa26e0040100017c0c38cadb' => 'tag #1 + card',
21	'd60017fe00000502e00401003123aa26e00401003123aa283124' => 'tag #1 + tag red-stripe',
22	};
23
24	=head1 NAME
25
26	3m-810 - support for 3M 810 RFID reader
27
28	=head1 SYNOPSIS
29
30	3m-810.pl [DEVICE [BAUD [DATA [PARITY [STOP [FLOW]]]]]]
31
32	=head1 DESCRIPTION
33
34	Communicate with 3M 810 RFID reader and document it's protocol
35
36	=head1 SEE ALSO
37
38	L<Device::SerialPort(3)>
39
40	L<perl(1)>
41
42	L<http://stackoverflow.com/questions/149617/how-could-i-guess-a-checksum-algorithm>
43
44	=head1 AUTHOR
45
46	Dobrica Pavlinusic <dpavlin@rot13.org> L<http://www.rot13.org/~dpavlin/>
47
48	=head1 COPYRIGHT AND LICENSE
49
50	This program is free software; you may redistribute it and/or modify
51	it under the same terms ans Perl itself.
52
53	=cut
54
55	# your serial port.
56	my ($device,$baudrate,$databits,$parity,$stopbits,$handshake)=@ARGV;
57	$device \|\|= "/dev/ttyUSB0";
58	$baudrate \|\|= "19200";
59	$databits \|\|= "8";
60	$parity \|\|= "none";
61	$stopbits \|\|= "1";
62	$handshake \|\|= "none";
63
64	my $port=new Device::SerialPort($device) \|\| die "new($device): $!\n";
65	$handshake=$port->handshake($handshake);
66	$baudrate=$port->baudrate($baudrate);
67	$databits=$port->databits($databits);
68	$parity=$port->parity($parity);
69	$stopbits=$port->stopbits($stopbits);
70
71	print "## using $device $baudrate $databits $parity $stopbits\n";
72
73	# Just in case: reset our timing and buffers
74	$port->lookclear();
75	$port->read_const_time(100);
76	$port->read_char_time(5);
77
78	# Turn on parity checking:
79	#$port->stty_inpck(1);
80	#$port->stty_istrip(1);
81
82	# initial hand-shake with device
83
84	cmd( 'D5 00 05 04 00 11 8C66', 'hw version?',
85	'D5 00 09 04 00 11 0A 05 00 02 7250', 'hw 10.5.0.2', sub {
86	print "hardware version ", join('.', unpack('CCCC', skip_assert(3) )), "\n";
87	});
88
89	cmd( 'D6 00 0C 13 04 01 00 02 00 03 00 04 00 AAF2','stats?',
90	'D6 00 0C 13 00 02 01 01 03 02 02 03 00 E778','FIXME: unimplemented', sub { assert() } );
91
92	# start scanning for tags
93
94	cmd( 'D6 00 05 FE 00 05 FA40', "XXX scan $_",
95	'D6 00 07 FE 00 00 05 00 C97B', 'no tag', sub {
96	dispatch(
97	'D6 00 0F FE 00 00 05 ',# 01 E00401003123AA26 941A # seen, serial length: 8
98	sub {
99	my $rest = shift \|\| die "no rest?";
100	my $nr = ord( substr( $rest, 0, 1 ) );
101	my $tags = substr( $rest, 1 );
102
103	my $tl = length( $tags );
104	die "wrong length $tl for $nr tags: ",dump( $tags ) if $tl =! $nr * 8;
105
106	my @tags;
107	push @tags, uc(unpack('H16', substr($tags, $_ * 8, 8))) foreach ( 0 .. $nr - 1 );
108	warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags ) if $debug;
109	print "seen $nr tags: ", join(',', @tags ) , "\n";
110
111	# XXX read first tag
112	read_tag( @tags );
113
114	}
115	) }
116
117	) foreach ( 1 .. 100 );
118
119	my $read_cached;
120
121	sub read_tag {
122	my ( $tag ) = @_;
123
124	print "read_tag $tag\n";
125	return if $read_cached->{ $tag }++;
126
127	cmd( "D6 00 0D 02 $tag 00 03 1CC4", 'read offset: 0 blocks: 3' );
128
129	# D6 00 1F 02 00 $tag 03 00 00 04 11 00 01 01 00 30 30 30 30 02 00 30 30 30 30 E5F4
130	warn "?? D6 00 1F 02 00 $tag 03 00 00 04 11 00 01 01 00 31 32 33 34 02 00 35 36 37 38 531F\n";
131	if (0) {
132	cmd( "D6 00 0D 02 $tag 03 04 3970", 'read offset: 3 blocks: 4' );
133
134	# D6 00 25 02 00 $tag 04 03 00 30 30 00 00 04 00 00 00 00 00
135	# $tag 05 00 00 00 00 00 06 00 00 00 00 00 B9BA
136	warn "?? D6 00 25 02 00 $tag 04 03 00 39 30 31 32 04 00 ....\n";
137	}
138	warn "?? D6 00 0F FE 00 00 05 01 $tag 941A ##### ready?\n";
139
140	}
141
142	for ( 1 .. 3 ) {
143
144	# ++-->type 00-0a
145	# D6 00 2A 04 E00401003123AA26 00 07 00 04 11 00 01 31 31 31 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1C D4
146	# D6 00 2A 04 E0 04 01 00 31 23 AA 26 00 07 00 04 11 00 06 32 32 32 32 32 32 32 32 32 32 32 00 00 00 00 00 00 00 00 00 00 00 00 00 32B7
147	# D6 00 2A 04 E0 04 01 00 31 23 AA 26 00 07 00 04 11 00 02 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 33 00 00 00 00 00 00 00 00 42 1F
148
149	cmd(' D6 00 2A 04 E00401003123AA26 00 07 00 04 11 00 01 30 30 30 30 30 30 30 30 30 30 00 00 00 00 00 00 00 00 00 00 00 00 00 00 8843', "write offset 0, block: 7 -- 0000000000 $_" );
150	warn "D6 00 0D 04 00 E00401003123AA26 07 CFF1 -- ack 7 block?\n";
151
152	}
153	warn " D6 00 0F FE 00 00 05 01 E00401003123AA26 941A\n";
154
155	cmd( 'D6 00 05 FE 00 05 FA 40', "port-write scan $_" ) foreach ( 1 .. 2 );
156
157	cmd('D6 00 0C 09 E00401003123AA26 D7 3AF0', 'checkin?',
158	'D6 00 0C 09 00 E00401003123AA26 6A44 -- no?' );
159	cmd('D6 00 0C 09 E00401003123AA26 DA EB5D', 'checkout?',
160	'D6 00 0C 09 00 E00401003123AA26 6A44 -- no?' );
161
162	cmd('D6 00 26 04 E00401003123AA26 00 06 00 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 A98B', 'blank offset: 0 blocks: 6',
163	'D6 00 0D 04 00 E00401003123AA26 06 DFD0 -- ack 6 blocks' ) foreach ( 1 .. 3 );
164
165	undef $port;
166	print "Port closed\n";
167
168	sub writechunk
169	{
170	my $str=shift;
171	my $count = $port->write($str);
172	print "#> ", as_hex( $str ), "\t[$count]\n";
173	}
174
175	sub as_hex {
176	my @out;
177	foreach my $str ( @_ ) {
178	my $hex = unpack( 'H*', $str );
179	$hex =~ s/(..)/$1 /g if length( $str ) > 2;
180	$hex =~ s/\s+$//;
181	push @out, $hex;
182	}
183	return join(' \| ', @out);
184	}
185
186	sub read_bytes {
187	my ( $len, $desc ) = @_;
188	my $data = '';
189	while ( length( $data ) < $len ) {
190	my ( $c, $b ) = $port->read(1);
191	#warn "## got $c bytes: ", as_hex($b), "\n";
192	$data .= $b;
193	}
194	$desc \|\|= '?';
195	warn "#< ", as_hex($data), "\t$desc\n" if $debug;
196	return $data;
197	}
198
199	our $assert;
200
201	# my $rest = skip_assert( 3 );
202	sub skip_assert {
203	assert( 0, shift );
204	}
205
206	sub assert {
207	my ( $from, $to ) = @_;
208
209	$from \|\|= 0;
210	$to = length( $assert->{expect} ) if ! defined $to;
211
212	my $p = substr( $assert->{payload}, $from, $to );
213	my $e = substr( $assert->{expect}, $from, $to );
214	warn "EXPECTED ",as_hex($e), " GOT ", as_hex($p), " [$from-$to] in ",dump( $assert ), "\n" if $e ne $p;
215
216	# return the rest
217	return substr( $assert->{payload}, $to );
218	}
219
220	our $dispatch;
221	sub dispatch {
222	my ( $pattern, $coderef ) = @_;
223	my $patt = substr( str2bytes($pattern), 3 ); # just payload
224	my $l = length($patt);
225	my $p = substr( $assert->{payload}, 0, $l );
226	warn "## dispatch pattern $pattern [$l] ",dump( $patt, $p ) if $debug;
227
228	if ( $assert->{payload} eq $assert->{expect} ) {
229	warn "## no dispatch, payload expected" if $debug;
230	} elsif ( $p eq $patt ) {
231	# if matched call with rest of payload
232	$coderef->( substr( $assert->{payload}, $l ) );
233	} else {
234	warn "## dispatch ignored" if $debug;
235	}
236	}
237
238	use Digest::CRC;
239
240	sub crcccitt {
241	my $bytes = shift;
242	my $crc = Digest::CRC->new(
243	# midified CCITT to xor with 0xffff instead of 0x0000
244	width => 16, init => 0xffff, xorout => 0xffff, refout => 0, poly => 0x1021, refin => 0,
245	) or die $!;
246	$crc->add( $bytes );
247	pack('n', $crc->digest);
248	}
249
250	# my $checksum = checksum( $bytes );
251	# my $checksum = checksum( $bytes, $original_checksum );
252	sub checksum {
253	my ( $bytes, $checksum ) = @_;
254
255	my $xor = crcccitt( substr($bytes,1) ); # skip D6
256	warn "## checksum ",dump( $bytes, $xor, $checksum ) if $debug;
257
258	my $len = ord(substr($bytes,2,1));
259	my $len_real = length($bytes);
260	print "length wrong: $len_real != $len\n" if $len_real != $len;
261
262	if ( defined $checksum && $xor ne $checksum ) {
263	print "checksum doesn't match: ", as_hex($xor), " != ", as_hex($checksum), " data: ", as_hex($bytes), "\n";
264	return $bytes . $xor;
265	}
266	return $bytes . $checksum;
267	}
268
269	sub readchunk {
270	my ( $parser ) = @_;
271
272	sleep 1; # FIXME remove
273
274	# read header of packet
275	my $header = read_bytes( 2, 'header' );
276	my $length = read_bytes( 1, 'length' );
277	my $len = ord($length);
278	my $data = read_bytes( $len, 'data' );
279
280	my $payload = substr( $data, 0, -2 );
281	my $payload_len = length($data);
282	warn "## payload too short $payload_len != $len\n" if $payload_len != $len;
283
284	my $checksum = substr( $data, -2, 2 );
285	checksum( $header . $length . $payload, $checksum );
286
287	print "<< ",as_hex( $header ), " [$len] ", as_hex( $payload ), " \| sum: ",as_hex($checksum),"\n";
288
289	$assert->{len} = $len;
290	$assert->{payload} = $payload;
291
292	$parser->( $len, $payload ) if $parser && ref($parser) eq 'CODE';
293
294	return $data;
295	}
296
297	sub str2bytes {
298	my $str = shift \|\| confess "no str?";
299	my $b = $str;
300	$b =~ s/\s+(\S\S)(\S\S)+\s*/ $1 $2/; # fix checksum
301	$b =~ s/\s+$//;
302	$b =~ s/\s+/\\x/g;
303	$b = '"\x' . $b . '"';
304	my $bytes = eval $b;
305	die $@ if $@;
306	warn "## str2bytes( $str ) => $b => ",as_hex($bytes) if $debug;
307	return $bytes;
308	}
309
310	sub cmd {
311	my ( $cmd, $cmd_desc, $expect, $expect_desc, $coderef ) = @_;
312	my $bytes = str2bytes( $cmd );
313
314	# fix checksum if needed
315	$bytes = checksum( substr( $bytes, 0, -2 ), substr( $bytes, -2, 2 ) );
316
317	warn ">> ", as_hex( $bytes ), "\t## $cmd_desc\n";
318	$assert->{send} = $cmd;
319	writechunk( $bytes );
320
321	if ( $expect ) {
322	warn "?? $expect", $expect_desc ? "\t## $expect_desc" : '', "\n";
323	$assert->{expect} = substr(str2bytes($expect), 3, -2); # just expected payload
324	readchunk( $coderef );
325	}
326	}
327