1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
|
#include "config.h"
#include <stdio.h>
#include <math.h>
#include <string.h>
#include "nmea.h"
extern struct OUTDATA gNMEAdata;
static void do_lat_lon(char *sentence, int begin);
static char *field(char *sentence, short n);
static void update_field_i(char *sentence, int fld, int *dest, int mask);
#if 0
static void update_field_f(char *sentence, int fld, double *dest, int mask);
#endif
/* ----------------------------------------------------------------------- */
/*
The time field in the GPRMC sentence is in the format hhmmss;
the date field is in the format ddmmyy. The output will
be in the format:
mm/dd/yyyy hh:mm:ss
01234567890123456789
*/
void processGPRMC(char *sentence)
{
char s[20], d[10];
int tmp;
sscanf(field(sentence, 9), "%s", d); /* Date: ddmmyy */
strncpy(s, d + 2, 2); /* copy month */
strncpy(s + 3, d, 2); /* copy date */
sscanf((d+4), "%2d", &tmp);
/* Tf.: Window the year from 1970 to 2069. This buys us some time. */
if (tmp < 70)
strncpy(s + 6, "20", 2); /* 21th century */
else
strncpy(s + 6, "19", 2); /* 20th century */
strncpy(s + 8, d + 4, 2); /* copy year */
sscanf(field(sentence, 1), "%s", d); /* Time: hhmmss */
strncpy(s + 11, d, 2); /* copy hours */
strncpy(s + 14, d + 2, 2); /* copy minutes */
strncpy(s + 17, d + 4, 2); /* copy seconds */
s[2] = s[5] = '/'; /* add the '/'s, ':'s, ' ' and string terminator */
s[10] = ' ';
s[13] = s[16] = ':';
s[19] = '\0';
strcpy(gNMEAdata.utc, s);
/* A = valid, V = invalid */
if (strcmp(field(sentence, 2), "V") == 0)
gNMEAdata.status = 0;
#if 0 /* Let the GGA sentence do the update so we catch diff fixes */
else
gNMEAdata.status = 0;
#endif
sscanf(field(sentence, 7), "%lf", &gNMEAdata.speed);
sscanf(field(sentence, 8), "%lf", &gNMEAdata.track);
do_lat_lon(sentence, 3);
}
/* ----------------------------------------------------------------------- */
void processGPVTG(char *sentence)
{
sscanf(field(sentence, 3), "%lf", &gNMEAdata.speed);
sscanf(field(sentence, 1), "%lf", &gNMEAdata.track);
}
/* ----------------------------------------------------------------------- */
void processGPGGA(char *sentence)
{
do_lat_lon(sentence, 2);
/* 0 = none, 1 = normal, 2 = diff */
sscanf(field(sentence, 6), "%d", &gNMEAdata.status);
if ((gNMEAdata.status > 0) && (gNMEAdata.mode < 2))
gNMEAdata.mode = 2;
if ((gNMEAdata.status < 1) && (gNMEAdata.mode > 1))
gNMEAdata.mode = 1;
sscanf(field(sentence, 7), "%d", &gNMEAdata.satellites);
sscanf(field(sentence, 9), "%lf", &gNMEAdata.altitude);
}
/* ----------------------------------------------------------------------- */
void processGPGSA(char *sentence)
{
/* 1 = none, 2 = 2d, 3 = 3d */
sscanf(field(sentence, 2), "%d", &gNMEAdata.mode);
if ((gNMEAdata.mode > 1) && (gNMEAdata.status < 1))
gNMEAdata.status = 1;
if ((gNMEAdata.mode < 2) && (gNMEAdata.status > 0))
gNMEAdata.status = 0;
sscanf(field(sentence, 15), "%lf", &gNMEAdata.pdop);
sscanf(field(sentence, 16), "%lf", &gNMEAdata.hdop);
sscanf(field(sentence, 17), "%lf", &gNMEAdata.vdop);
}
/* ----------------------------------------------------------------------- */
void processGPGSV(char *sentence)
{
int n, m, f = 4;
sscanf(field(sentence, 2), "%d", &n);
update_field_i(sentence, 3, &gNMEAdata.in_view, C_SAT);
n = (n - 1) * 4;
m = n + 4;
while (n < gNMEAdata.in_view && n < m) {
update_field_i(sentence, f++, &gNMEAdata.PRN[n], C_SAT);
update_field_i(sentence, f++, &gNMEAdata.elevation[n], C_SAT);
update_field_i(sentence, f++, &gNMEAdata.azimuth[n], C_SAT);
if (*(field(sentence, f)))
update_field_i(sentence, f, &gNMEAdata.ss[n], C_SAT);
f++;
n++;
}
}
/* ----------------------------------------------------------------------- */
void processPRWIZCH(char *sentence)
{
int i;
for (i = 0; i < 12; i++) {
update_field_i(sentence, 2 * i + 1, &gNMEAdata.Zs[i], C_ZCH);
update_field_i(sentence, 2 * i + 2, &gNMEAdata.Zv[i], C_ZCH);
}
gNMEAdata.ZCHseen = 1;
}
/* ----------------------------------------------------------------------- */
static void do_lat_lon(char *sentence, int begin)
{
double lat, lon, d, m;
char str[20], *p;
if (*(p = field(sentence, begin + 0)) != '\0') {
strncpy(str, p, 20);
sscanf(p, "%lf", &lat);
m = 100.0 * modf(lat / 100.0, &d);
lat = d + m / 60.0;
p = field(sentence, begin + 1);
if (*p == 'S')
lat = -lat;
if (gNMEAdata.latitude != lat) {
gNMEAdata.latitude = lat;
gNMEAdata.cmask |= C_LATLON;
}
}
if (*(p = field(sentence, begin + 2)) != '\0') {
strncpy(str, p, 20);
sscanf(p, "%lf", &lon);
m = 100.0 * modf(lon / 100.0, &d);
lon = d + m / 60.0;
p = field(sentence, begin + 3);
if (*p == 'W')
lon = -lon;
if (gNMEAdata.longitude != lon) {
gNMEAdata.longitude = lon;
gNMEAdata.cmask |= C_LATLON;
}
}
}
static void update_field_i(char *sentence, int fld, int *dest, int mask)
{
int tmp;
sscanf(field(sentence, fld), "%d", &tmp);
if (tmp != *dest) {
*dest = tmp;
gNMEAdata.cmask |= mask;
}
}
#if 0
static void update_field_f(char *sentence, int fld, double *dest, int mask)
{
double tmp;
scanf(field(sentence, fld), "%lf", &tmp);
if (tmp != *dest) {
*dest = tmp;
gNMEAdata.cmask |= mask;
}
}
#endif
/* ----------------------------------------------------------------------- */
short checksum(char *sentence)
{
unsigned char sum = '\0';
char c, *p = sentence, csum[3];
while ((c = *p++) != '*')
sum ^= c;
sprintf(csum, "%02X", sum);
return (strncmp(csum, p, 2) == 0);
}
void add_checksum(char *sentence)
{
unsigned char sum = '\0';
char c, *p = sentence;
while ((c = *p++) != '*')
sum ^= c;
sprintf(p, "%02X\r\n", sum);
}
/* ----------------------------------------------------------------------- */
/* field() returns a string containing the nth comma delimited
field from sentence string
*/
static char *field(char *sentence, short n)
{
static char result[100];
char *p = sentence;
while (n-- > 0)
while (*p++ != ',');
strcpy(result, p);
p = result;
while (*p && *p != ',' && *p != '*' && *p != '\r')
p++;
*p = '\0';
return result;
}
|
