2768a009e92bbf74401deccf70db33d688b05da0
[dweather.git] / loop.pl
1 #!/usr/bin/perl
2 use strict;
3
4 use v5.10.1;
5
6 use Mojolicious::Lite;
7 use Serial;
8 use Mojo::IOLoop;
9 use Mojo::IOLoop::Stream;
10 use Mojo::Transaction::WebSocket;
11 #use Mojo::JSON  qw(decode_json encode_json);
12 use JSON;
13 use Debug;
14 use SMGLog;
15 use Math::Round qw(nearest);
16 use File::Copy;
17 use Data::Random qw(rand_chars);
18 use IO::File;
19
20 use constant pi => 3.14159265358979; 
21
22 my $devname = "/dev/davis";
23 my $datafn = ".loop_data";
24 my $dataf;
25
26 my $poll_interval = 2.5;
27 my $rain_mult = 0.2;                            # 0.1 or 0.2 mm or 0.01 inches
28 my $tid;
29 my $rid;
30 our $did;
31 my $nlcount;
32 my $state = "ready";
33 my $buf;
34 my $dbg;
35 my $ser;                                                        # the serial port Mojo::IOLoop::Stream
36 my $last_min_h;
37 my $last_hour_h;
38
39 our $json = JSON->new->canonical(1);
40 our $WS = {};                                   # websocket connections
41
42 our $ld = {};
43 our @last10minsr = ();
44 our @last5daysh = ();
45
46 our $loop_count;                                # how many LOOPs we have done, used as start indicator
47
48 our     @crc_table = (
49                                   0x0, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
50                                   0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
51                                   0x1231, 0x210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
52                                   0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
53                                   0x2462, 0x3443, 0x420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
54                                   0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
55                                   0x3653, 0x2672, 0x1611, 0x630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
56                                   0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
57                                   0x48c4, 0x58e5, 0x6886, 0x78a7, 0x840, 0x1861, 0x2802, 0x3823,
58                                   0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
59                                   0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0xa50, 0x3a33, 0x2a12,
60                                   0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
61                                   0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0xc60, 0x1c41,
62                                   0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
63                                   0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0xe70,
64                                   0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
65                                   0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
66                                   0x1080, 0xa1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
67                                   0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
68                                   0x2b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
69                                   0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
70                                   0x34e2, 0x24c3, 0x14a0, 0x481, 0x7466, 0x6447, 0x5424, 0x4405,
71                                   0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
72                                   0x26d3, 0x36f2, 0x691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
73                                   0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
74                                   0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x8e1, 0x3882, 0x28a3,
75                                   0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
76                                   0x4a75, 0x5a54, 0x6a37, 0x7a16, 0xaf1, 0x1ad0, 0x2ab3, 0x3a92,
77                                   0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
78                                   0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0xcc1,
79                                   0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
80                                   0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0xed1, 0x1ef0
81                                  );
82
83 our %bar_trend;
84
85 $bar_trend{-60} = "Falling Rapidly";
86 $bar_trend{196} = "Falling Rapidly";
87 $bar_trend{-20} = "Falling Slowly";
88 $bar_trend{236} = "Falling Slowly";
89 $bar_trend{0} = "Steady";
90 $bar_trend{20} = "Rising Slowly";
91 $bar_trend{60} = "Rising Rapidly";
92
93 our $ending = 0;
94
95 $SIG{TERM} = $SIG{INT} = sub {++$ending; Mojo::IOLoop->stop;};
96 $SIG{HUP} = 'IGNORE';
97
98
99 # WebSocket weather service
100 websocket '/weather' => sub {
101   my $c = shift;
102   my $msg = shift;
103   my $tx = $c->tx;
104
105   # Opened
106   app->log->debug('WebSocket opened.');
107   dbg 'WebSocket opened' if isdbg 'chan';
108   $WS->{$tx} = $tx; 
109
110   # send historical data
111   $c->send($ld->{lasthour_h}) if exists $ld->{lasthour_h};
112   $c->send($ld->{lastmin_h}) if exists $ld->{lastmin_h};
113
114   # send the 5 days worth of data to the graph
115   say "last10min = " . scalar @last10minsr . " last5day = " . scalar  @last5daysh;
116   $c->send($_) for @last10minsr;
117   $c->send($_) for @last5daysh;
118   
119   # disable timeout
120   $c->inactivity_timeout(3615);
121  
122   # Incoming message
123   $c->on(
124                  message => sub {
125                          my ($c, $msg) = @_;
126                          dbg "websocket: text $msg" if isdbg 'chan';
127                  },
128                  json => sub {
129                          my ($c, $msg) = @_;
130                          dbg "websocket: json $msg" if isdbg 'chan';
131                  }
132   );
133  
134   # Closed
135   $c->on(finish => sub {
136     my ($c, $code, $reason) = @_;
137     app->log->debug("WebSocket closed with status $code.");
138         dbg "websocket closed with status $code" if isdbg 'chan';
139         delete $WS->{$tx};
140   });
141 };
142
143 get '/' => {template => 'index'};
144
145
146 dbginit();
147 if (@ARGV) {
148         dbgadd(@ARGV);
149
150 dbgadd('chan');
151
152 dbg '***';
153 dbg "*** starting $0";
154 dbg '***';
155
156 read_ld();
157
158 my $tnow = time;
159 my $dayno = int ($tnow/86400);
160 @last5daysh = grab_history(SMGLog->new("day"), "h", $tnow-(86400*5), $_) for ($dayno-4, $dayno-3, $dayno-2, $dayno-1, $dayno);  
161 @last10minsr = map {my ($t, $js) = split(/\s/, $_, 2); $js} grab_history(SMGLog->new("debug"), "r", $tnow-(60*3), $dayno);
162
163 our $dlog = SMGLog->new("day");
164 dbg "before next tick";
165 Mojo::IOLoop->next_tick(sub { loop() });        
166 dbg "before app start";
167 app->start;
168 dbg "after app start";
169
170 write_ld();
171 $dataf->close if $dataf;
172 undef $dataf;
173
174
175 # move all the files along one 
176 cycle_loop_data_files();
177
178 dbg '***';
179 dbg "*** ending $0";
180 dbg '***';
181
182 exit 0;
183
184 ##################################################################################
185         
186 sub loop
187 {
188         dbg "last_min: " . scalar gmtime($ld->{last_min});
189         dbg "last_hour: " . scalar gmtime($ld->{last_hour});
190         
191         $did = Mojo::IOLoop->recurring(1 => sub {$dlog->flushall});
192         
193         do_reopen($devname);
194 }
195
196
197
198 sub on_read
199 {
200         my ($ser, $d) = @_;
201         $buf .= $d;
202         $d =~ s/([\%\x00-\x1f\x7f-\xff])/sprintf("%%%02X", ord($1))/eg; 
203         dbg "read added '$d' buf lth=" . length $buf if isdbg 'raw';
204         if ($state eq 'waitnl' && $buf =~ /[\cJ\cM]+/) {
205                 dbg "Got \\n" if isdbg 'state';
206                 Mojo::IOLoop->remove($tid) if $tid;
207                 undef $tid;
208                 undef $buf;
209                 $nlcount = 0;
210                 $ser->write("LPS 1 1\n");
211                 chgstate("waitloop");
212         } elsif ($state eq "waitloop") {
213                 if ($buf =~ /\x06/) {
214                         dbg "Got ACK 0x06" if isdbg 'state';
215                         chgstate('waitlooprec');
216                         undef $buf;
217                 }
218         } elsif ($state eq 'waitlooprec') {
219                 if (length $buf >= 99) {
220                         dbg "got loop record" if isdbg 'chan';
221                         chgstate('');
222                         process($buf);
223                         undef $buf;
224                 }
225         }
226 }
227
228 sub start_loop
229 {
230         $nlcount = 1;
231         dbg "start_loop writing $nlcount \\n" if isdbg 'state';
232         $ser->write("\n");
233         Mojo::IOLoop->remove($tid) if $tid;
234         undef $tid;
235         $tid = Mojo::IOLoop->recurring(0.6 => sub {
236                                                                            if (++$nlcount > 10) {
237                                                                                    dbg "\\n count > 10, closing connection" if isdbg 'chan';
238                                                                                    do_reopen($devname);
239                                                                                    return;
240                                                                            }
241                                                                            dbg "writing $nlcount \\n" if isdbg 'state'; 
242                                                                            $ser->write("\n");
243                                                                    });
244         chgstate("waitnl");
245 }
246
247 sub chgstate
248 {
249         dbg "state '$state' -> '$_[0]'" if isdbg 'state';
250         $state = $_[0];
251 }
252
253 sub do_reopen
254 {
255         my $name = shift;
256         dbg "do reopen on '$name' ending $ending";
257         unless ($ending) {
258                 $ser = do_open($name);
259                 start_loop();
260                 chgstate('');
261                 $nlcount = 0;
262                 Mojo::IOLoop->start unless Mojo::IOLoop->is_running;
263         }
264 }
265
266 sub do_open
267 {
268         my $name = shift;
269
270         $ser->close if $ser;
271         undef $ser;
272
273         my $ob = Serial->new($name, 19200) || die "$name $!\n";
274         dbg "streaming $name fileno(" . fileno($ob) . ")" if isdbg 'chan';
275         
276         my $ser = Mojo::IOLoop::Stream->new($ob);
277         $ser->on(error=>sub {dbg "serial $_[1]"; do_reopen($name) unless $ending});
278         $ser->on(close=>sub {dbg "serial closing"; do_reopen($name) unless $ending});
279         $ser->on(timeout=>sub {dbg "serial timeout";});
280         $ser->on(read=>sub {on_read(@_)});
281         $ser->start;
282
283         Mojo::IOLoop->remove($tid) if $tid;
284         undef $tid;
285         Mojo::IOLoop->remove($rid) if $rid;
286         undef $rid;
287         $rid = Mojo::IOLoop->recurring($poll_interval => sub {
288                                                                            start_loop() if !$state;
289                                                                    });
290         chgstate('');
291         $nlcount = 0;
292         
293         return $ser;
294 }
295
296 my @min;
297 my @hour;
298
299 sub process
300 {
301         my $blk = shift;
302         my $loo =  substr $blk,0,3;
303         unless ( $loo eq 'LOO') {
304                 dbg "Block invalid loo -> $loo" if isdbg 'chan'; return;
305         }
306
307         my $tmp;
308         my $temp;
309         my $rain;
310         my %h;
311
312         my $crc_calc = CRC_CCITT($blk);
313
314         if ($crc_calc==0) {
315
316                 # Common ones
317                 $tmp = unpack("s", substr $blk,7,2) / 1000;
318                 $h{Pressure} = nearest(1, in2mb($tmp));
319
320                 $tmp = unpack("s", substr $blk,9,2) / 10;
321                 $h{Temp_In} = nearest(0.1, f2c($tmp));
322
323                 $temp  = nearest(0.1, f2c(unpack("s", substr $blk,12,2) / 10));
324                 $h{Temp_Out}  = $temp;
325                 if ($temp > 75 || $temp < -75) {
326                         dbg "LOOP Temperature out of range ($temp), record ignored";
327                         return;
328                 }
329
330                 $tmp = unpack("C", substr $blk,14,1);
331                 $h{Wind} = nearest(0.1, mph2mps($tmp));
332                 $h{Dir}     = unpack("s", substr $blk,16,2)+0;
333
334                 my $wind = {w => $h{Wind}, d => $h{Dir}};
335                 $wind = 0 if $wind == 255;
336                 push @{$ld->{wind_min}}, $wind;
337
338                 $tmp = int(unpack("C", substr $blk,33,1)+0);
339                 if ($tmp > 100) {
340                         dbg "LOOP Outside Humidity out of range ($tmp), record ignored";
341                         return;
342                 }
343                 $h{Humidity_Out} = $tmp;
344                 $tmp = int(unpack("C", substr $blk,11,1)+0);
345                 if ($tmp > 100) {
346                         dbg "LOOP Inside Humidity out of range ($tmp), record ignored";
347                         return;
348                 }
349                 $h{Humidity_In}  = $tmp;
350                 
351
352                 $tmp = unpack("C", substr $blk,43,1)+0;
353                 $h{UV} = $tmp unless $tmp >= 255;
354                 $tmp = unpack("s", substr $blk,44,2)+0; # watt/m**2
355                 $h{Solar} = $tmp unless $tmp >= 32767;
356
357                 #       $h{Rain_Rate}  = nearest(0.1,unpack("s", substr $blk,41,2) * $rain_mult);
358                 $rain = $h{Rain_Day}   = nearest(0.1, unpack("s", substr $blk,50,2) * $rain_mult);
359                 my $delta_rain = $h{Rain} = nearest(0.1, ($rain >= $ld->{last_rain} ? $rain - $ld->{last_rain} : $rain)) if $loop_count;
360                 $ld->{last_rain} = $rain;
361
362                 # what sort of packet is it?
363                 my $sort =  unpack("C", substr $blk,4,1);
364                 if ($sort) {
365
366                         # Newer LOOP2 packet
367                         $tmp = unpack("C", substr $blk,18,2);
368                         #               $h{Wind_Avg_10} = nearest(0.1,mph2mps($tmp/10));
369                         $tmp = unpack("C", substr $blk,20,2);
370                         #               $h{Wind_Avg_2} = nearest(0.1,mph2mps($tmp/10));
371                         $tmp = unpack("C", substr $blk,22,2);
372                         #               $h{Wind_Gust_10} = nearest(0.1,mph2mps($tmp/10));
373
374                         #               $h{Dir_Avg_10} = unpack("C", substr $blk,24,2)+0;
375                         $tmp = unpack("C", substr $blk,30,2);
376                         $h{Dew_Point} = nearest(0.1, f2c($tmp));
377
378                 } else {
379
380                         # Older LOOP packet
381                         $tmp = unpack("C", substr $blk,15,1);
382                         #               $h{Wind_Avg_10} = nearest(0.1,mph2mps($tmp));
383                         $h{Dew_Point}  = nearest(0.1, dew_point($h{Temp_Out}, $h{Humidity_Out}));
384                         $h{Rain_Month}  = nearest(0.1, unpack("s", substr $blk,52,2) * $rain_mult);
385                         $h{Rain_Year}  = nearest(0.1, unpack("s", substr $blk,54,2) * $rain_mult);
386                 }
387
388                 my $ts = time;
389                 my $s;
390                 my $dayno = int($ts/86400);
391                 if ($dayno > $ld->{last_day}) {
392                         $ld->{Temp_Out_Max} = $ld->{Temp_Out_Min} = $temp;
393                         $ld->{Temp_Out_Max_T} = $ld->{Temp_Out_Min_T} = clocktime($ts, 0);
394                         $ld->{last_day} = $dayno;
395                         write_ld();
396                         cycle_loop_data_files();
397                 }
398                 if ($temp > $ld->{Temp_Out_Max}) {
399                         $ld->{Temp_Out_Max} = $temp;
400                         $ld->{Temp_Out_Max_T} = clocktime($ts, 0);
401                         write_ld();
402                 }
403                 if ($temp < $ld->{Temp_Out_Min}) {
404                         $ld->{Temp_Out_Min} = $temp;
405                         $ld->{Temp_Out_Min_T} = clocktime($ts, 0);
406                         write_ld();
407                 }
408
409                 if ($ts >= $ld->{last_hour} + 1800) {
410                         $h{Pressure_Trend}    = unpack("C", substr $blk,3,1);
411                         $h{Pressure_Trend_txt} = $bar_trend{$h{Pressure_Trend}};
412                         $h{Batt_TX_OK}  = (unpack("C", substr $blk,86,1)+0) ^ 1;
413                         $h{Batt_Console}  = nearest(0.01, unpack("s", substr $blk,87,2) * 0.005859375);
414                         $h{Forecast_Icon}  = unpack("C", substr $blk,89,1);
415                         $h{Forecast_Rule}  = unpack("C", substr $blk,90,1);
416                         $h{Sunrise}  = sprintf( "%04d", unpack("S", substr $blk,91,2) );
417                         $h{Sunrise}  =~ s/(\d{2})(\d{2})/$1:$2/;
418                         $h{Sunset}   = sprintf( "%04d", unpack("S", substr $blk,93,2) );
419                         $h{Sunset}  =~ s/(\d{2})(\d{2})/$1:$2/;
420                         $h{Temp_Out_Max} = $ld->{Temp_Out_Max};
421                         $h{Temp_Out_Min} = $ld->{Temp_Out_Min};
422                         $h{Temp_Out_Max_T} = $ld->{Temp_Out_Max_T};
423                         $h{Temp_Out_Min_T} = $ld->{Temp_Out_Min_T};
424                         
425
426                         if ($loop_count) {      # i.e not the first
427                                 my $a = wind_average(scalar @{$ld->{wind_hour}} ? @{$ld->{wind_hour}} : {w => $h{Wind}, d => $h{Dir}});
428
429                                 $h{Wind_1h} = nearest(0.1, $a->{w});
430                                 $h{Dir_1h} = nearest(0.1, $a->{d});
431
432                                 $a = wind_average(@{$ld->{wind_min}});
433                                 $h{Wind_1m} = nearest(0.1, $a->{w});
434                                 $h{Dir_1m} = nearest(1, $a->{d});
435
436                                 ($h{Rain_1m}, $h{Rain_1h}, $h{Rain_24h}) = calc_rain($rain);
437                         }
438                         $ld->{last_rain_min} = $ld->{last_rain_hour} = $rain;
439
440                         $last_hour_h = {%h};
441                         $s = genstr($ts, 'h', \%h);
442                         $ld->{lasthour_h} = $s;
443                         
444                         $ld->{last_hour} = int($ts/1800)*1800;
445                         $ld->{last_min} = int($ts/60)*60;
446                         @{$ld->{wind_hour}} = ();
447                         @{$ld->{wind_min}} = ();
448
449                         if ($s) {
450                                 output_str($s, 1);
451                                 push @last5daysh, $s;
452                                 shift @last5daysh if @last5daysh > 5*24;
453                         }
454                         write_ld();
455                         
456                 } elsif ($ts >= $ld->{last_min} + 60) {
457                         my $a = wind_average(@{$ld->{wind_min}});
458                         my %save;
459
460                         push @{$ld->{wind_hour}}, $a;
461
462                         if ($loop_count) {      # i.e not the first
463                                 my $rm;
464                                 
465                                 $h{Wind_1m} = nearest(0.1, $a->{w});
466                                 $h{Dir_1m} = nearest(1, $a->{d});
467                                 ($h{Rain_1m}, $h{Rain_1h}, $h{Rain_24h}) = calc_rain($rain);
468                         }
469                         $ld->{last_rain_min} = $rain;
470
471                         $h{Temp_Out_Max} = $ld->{Temp_Out_Max};
472                         $h{Temp_Out_Min} = $ld->{Temp_Out_Min};
473                         $h{Temp_Out_Max_T} = $ld->{Temp_Out_Max_T};
474                         $h{Temp_Out_Min_T} = $ld->{Temp_Out_Min_T};
475
476                         $last_min_h = {%h};
477                         $s = genstr($ts, 'm', \%h);
478                         $ld->{lastmin_h} = $s;
479                         
480                         $ld->{last_min} = int($ts/60)*60;
481                         @{$ld->{wind_min}} = ();
482                         
483                         output_str($s, 1) if $s;
484                         write_ld();
485
486                 } else {
487                         my $o = gen_hash_diff($ld->{last_h}, \%h);
488                         if ($o) {
489                                 $s = genstr($ts, 'r', $o);
490                                 push @last10minsr, $s;
491                                 shift @last10minsr if @last10minsr > 240;
492                         }
493                         else {
494                                 dbg "loop rec not changed" if isdbg 'chan';
495                         }
496                         output_str($s, 0) if $s;
497                 }
498                 $ld->{last_h} = \%h;
499                 ++$loop_count;
500         } else {
501                 dbg "CRC check failed for LOOP data!";
502         }
503         return;
504 }
505
506 sub genstr
507 {
508         my $ts = shift;
509         my $let = shift;
510         my $h = shift;
511         
512         my $j =  $json->encode($h);
513         my $tm = clocktime($ts, 1);
514         return qq|{"tm":"$tm","t":$ts,"$let":$j}|;
515 }
516
517 sub clocktime
518 {
519         my $ts = shift;
520         my $secsreq = shift;
521         my ($sec,$min,$hr) = (gmtime $ts)[0,1,2];
522         my $s;
523         if ($secsreq) {
524                 $s = sprintf "%02d:%02d:%02d", $hr, $min, $sec;
525         } else {
526                 $s = sprintf "%02d:%02d", $hr, $min;
527         }
528         return $s;
529 }
530
531 sub output_str
532 {
533         my $s = shift;
534         my $logit = shift;
535         
536         dbg $s;
537 #       say $s;
538         $dlog->writenow($s) if $logit;
539         foreach my $ws (keys $WS) {
540                 my $tx = $WS->{$ws};
541                 if ($tx) {
542                         $tx->send($s);
543                 } else {
544                         delete $WS->{$tx};
545                 }
546         }
547 }
548
549 sub gen_hash_diff
550 {
551         my $last = shift;
552         my $now = shift;
553         my %o;
554         my $count;
555
556         while (my ($k, $v) = each %$now) {
557                 if (!exists $last->{$k} || $last->{$k} ne $now->{$k}) {
558                         $o{$k} = $v;
559                         ++$count;
560                 }
561         }
562         return $count ? \%o : undef;
563 }
564
565 sub dew_point
566 {
567         my $temp = shift @_;
568         my $rh   = shift @_;
569
570         #  Using the simplified approximation for dew point
571         #  Accurate to 1 degree C for humidities > 50 %
572         #  http://en.wikipedia.org/wiki/Dew_point
573
574         my $dewpoint = $temp - ((100 - $rh) / 5);
575
576         # this is the more complete one (which doesn't work)
577         #my $a = 6.1121;
578         #my $b = 18.678;
579         #my $c = 257.14;
580         #my $ytrh = log(($rh/100) + ($b * $temp) / ($c + $temp));
581         #my $dewpoint = ($c * $ytrh) / ($b - $ytrh); 
582
583         return $dewpoint;
584 }
585
586 sub CRC_CCITT
587 {
588     # Expects packed data...
589     my $data_str = shift @_;
590
591         my $crc = 0;
592         my @lst = split //, $data_str;
593         foreach my $data (@lst) {
594                 my $data = unpack("c",$data);
595
596                 my $crc_prev = $crc;
597                 my $index = $crc >> 8 ^ $data;
598                 my $lhs = $crc_table[$index];
599                 #print "lhs=$lhs, crc=$crc\n";
600                 my $rhs = ($crc << 8) & 0xFFFF;
601                 $crc = $lhs ^ $rhs;
602
603
604         }
605
606         return $crc;
607 }
608
609 sub f2c
610 {
611         return ($_[0] - 32) * 5/9;
612 }
613
614 sub mph2mps
615 {
616         return $_[0] * 0.44704;
617 }
618
619 sub in2mb
620 {
621         return $_[0] * 33.8637526;
622 }
623
624 sub wind_average
625 {
626         my ($sindir, $cosdir, $wind);
627         my $count;
628         
629         foreach my $r (@_) {
630                 $wind += $r->{w};
631                 $sindir += sin(d2r($r->{d})) * $r->{w};
632                 $cosdir += cos(d2r($r->{d})) * $r->{w};
633                 ++$count;
634         }
635
636         my $avhdg = r2d(atan2($sindir, $cosdir));
637         $avhdg += 360 if $avhdg < 0; 
638         return {w => nearest(0.1,$wind / $count), d => nearest(0.1,$avhdg)};
639 }
640
641 # radians to degrees
642 sub r2d
643 {
644     my $n = shift;
645     return ($n / pi) * 180;
646 }
647
648 # degrees to radians
649 sub d2r 
650 {
651     my $n = shift;
652     return ($n / 180) * pi;
653 }
654
655 sub calc_rain
656 {
657         my $rain = shift;
658         
659         $ld->{rain24} ||= [];
660         
661         my $Rain_1h = nearest(0.1, $rain >= $ld->{last_rain_hour} ? $rain - $ld->{last_rain_hour} : $rain); # this is the rate for this hour, so far
662         my $rm = nearest(0.1, $rain >= $ld->{last_rain_min} ? $rain - $ld->{last_rain_min} : $rain);
663         my $Rain_1m = nearest(0.1, $rm);
664         push @{$ld->{rain24}}, $Rain_1m;
665         $ld->{rain_24} += $rm;
666         while (@{$ld->{rain24}} > 24*60) {
667                 $ld->{rain_24} -= shift @{$ld->{rain24}};
668         }
669         my $Rain_24h = nearest(0.1, $ld->{rain_24});
670         return ($Rain_1m, $Rain_1h, $Rain_24h);
671 }
672
673 sub read_ld
674 {
675         unless ($dataf) {
676                 $dataf = IO::File->new("+>> $datafn") or die "cannot open $datafn $!";
677                 $dataf->autoflush(1);
678         }
679
680         seek $dataf, 0, 0;
681         my $s = <$dataf>;
682         chomp $s;
683         dbg "read loop data: $s" if isdbg 'json';
684         $ld = $json->decode($s) if length $s;
685         
686         # sort out rain stats
687         my $c;
688         if ($ld->{rain24} && ($c = @{$ld->{rain24}}) < 24*60) {
689                 my $diff = 24*60 - $c;
690                 unshift @{$ld->{rain24}}, 0 for 0 .. $diff;  
691         }
692         my $rain;
693         
694         if ($ld->{rain24}) {
695                 $rain += $_ for @{$ld->{rain24}};
696         }
697         
698         $ld->{rain_24} = nearest(0.1, $rain);
699         delete $ld->{hour};
700         delete $ld->{min};
701 }
702
703 sub write_ld
704 {
705         unless ($dataf) {
706                 $dataf = IO::File->new("+>> $datafn") or die "cannot open $datafn $!";
707                 $dataf->autoflush(1);
708         }
709
710         seek $dataf, 0, 0;
711         truncate $dataf, 0;
712         $ld->{ts} = time;
713         my $s = $json->encode($ld);
714         dbg "write loop data: $s" if isdbg 'json';
715         print $dataf "$s\n";
716 }
717
718 sub cycle_loop_data_files
719 {
720         $dataf->close if $dataf;
721         undef $dataf;
722         
723         rename "$datafn.oooo", "$datafn.ooooo";
724         rename "$datafn.ooo", "$datafn.oooo";
725         rename "$datafn.oo", "$datafn.ooo";
726         rename "$datafn.o", "$datafn.oo";
727         copy $datafn, "$datafn.o";
728 }
729
730 sub grab_history
731 {
732         my $lg = shift;
733         my $let = shift;
734         my $start = shift || time - 86400;
735         my $dayno = shift;
736         my @out;
737         
738         if ($lg->open($dayno, 'r+')) {
739                 while (my $l = $lg->read) {
740                         next unless $l =~ /,"$let":/;
741                         my ($t) = $l =~ /"t":(\d+)/;
742                         if ($t && $t >= $start) {
743                                 push @out, $l;
744                         }
745                 }
746                 $lg->close;
747         }
748         return @out;
749 }