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comparison util.c @ 0:9dab44dcb331

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Initial commit of Greg's code from http://www.lemis.com/grog/tmp/wh1080.tar.gz
author Daniel O'Connor <darius@dons.net.au>
date Tue, 09 Feb 2010 13:44:25 +1030
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children b22a888eb975
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-1:000000000000 0:9dab44dcb331
1 /*
2 * WH-1080 data input utility.
3 * Utility functions
4 *
5 * Greg Lehey, 22 November 2009
6 *
7 * $Id: util.c,v 1.6 2009/12/18 02:13:23 grog Exp $
8 */
9
10 #include "wh1080.h"
11
12 /* Used in many places, but not here */
13 char *wind_directions [] = {"N", "NNE", "NE", "ENE", "E", "ESE", "SE", "SSE",
14 "S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW "};
15
16 float print_previous_rain; /* counter for print_readings */
17
18 /* Print out readings */
19 void print_readings (struct readings *readings)
20 {
21 static int lines = 0;
22 char timestamp [STAMPSIZE];
23
24 if (lines == 0)
25 printf ("\n"
26 " Page sv IT IH IDP OT OH ODP hPa SL abs rel Wind Gust Dir Rain CR PR \n");
27
28 strftime (timestamp, STAMPSIZE, "%F %T", localtime (&readings->timestamp)); /* format time and date */
29
30 printf ("%17s %5x %3d %5.1f %3d %5.1f %5.1f %3d %5.1f %6.1f %6.1f %6.1f %6.1f %5.1f %5.1f %3s %4.1f %4.1f %4.1f\n",
31 timestamp, /* current time */
32 readings->page, /* machine page number */
33 readings->last_save_mins, /* last save minutes (?) */
34 readings->inside_temp, /* inside temperature */
35 readings->inside_humidity, /* humidity in percent */
36 readings->inside_dewpoint, /* inside dewpoint */
37 readings->outside_temp, /* outside temperature */
38 readings->outside_humidity, /* humidity in percent */
39 readings->outside_dewpoint, /* outside dewpoint */
40 readings->pressure, /* absolute pressure, hPa */
41 readings->pressure_sea_level, /* sea level pressure, hPa */
42 readings->page1_abs_pressure, /* absolute pressure, hPa */
43 readings->page1_rel_pressure, /* relative pressure, hPa */
44 readings->wind_speed, /* wind speed in km/h */
45 readings->wind_gust, /* wind gust speed in km/h */
46 readings->wind_direction_text, /* wind direction */
47 readings->rain - print_previous_rain, /* delta rainfall in mm */
48 readings->rain, /* current rainfall in mm */
49 readings->previous_rain ); /* previous rainfall in mm */
50 print_previous_rain = readings->rain; /* reported this far */
51 if (++lines > 60)
52 lines = 0;
53 }
54
55 /*
56 * Calculate dewpoint temperature. Replace this with something with better references.
57 */
58 float dewpoint (float temp, int humidity)
59 {
60 float Es; /* saturated water vapour pressure at dry-bulb temperature */
61 float Ep; /* partial pressure at this humidity */
62
63 Es = 6.11 * pow (10.0, 7.5 * (temp / (237.7 + temp)));
64 Ep = (humidity * Es) / 100;
65 return (-430.22 + 237.7 * log (Ep)) / (-log (Ep) + 19.08);
66 }
67
68 /*
69 * Calculate inside and outside dewpoints and store in the record.
70 */
71 void set_dewpoints (struct readings *readings)
72 {
73 readings->inside_dewpoint = dewpoint (readings->inside_temp, readings->inside_humidity);
74 readings->outside_dewpoint = dewpoint (readings->outside_temp, readings->outside_humidity);
75 }
76
77 /*
78 * Convert pressure to sea-level pressure. The barometer is in the inside unit,
79 * so we use the internal temperature as a base.
80 */
81 void set_sea_level_pressure (struct readings *readings)
82 {
83 float e = - config.elevation / (KELVIN (readings->inside_temp) * 29.263);
84
85 e = exp (e);
86
87 readings->pressure_sea_level = readings->pressure / e;
88 }
89
90 /*
91 * Simplified date conversion.
92 * text must be big enough for format; we don't check.
93 */
94 void datetext (time_t date, char *text, char *format)
95 {
96 struct tm *date_tm; /* struct tm format of date */
97
98 date_tm = localtime (&date); /* and in struct tm format */
99 strftime (text, 64, format, date_tm);
100 }