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
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
|
#!/usr/bin/env python
#
# gpsd.py -- low-level interface to an NMEA GPS
#
# Like libgpsd in C, but handles only straight NMEA devices (not Zodiac).
import termios, os, fcntl, copy, time, math, struct
import gps
class NMEA:
def __init__(self, data, logger=None):
self.data = data
if logger:
self.logger = logger
else:
self.logger = lambda *args: None
def add_checksum(self,sentence):
csum = 0
for c in sentence:
csum = csum ^ ord(c)
return sentence + "%02X" % csum + "\r\n"
def checksum(self,sentence, cksum):
csum = 0
for c in sentence:
csum = csum ^ ord(c)
return "%02X" % csum == cksum
def __do_lat_lon(self, words):
# The Navman sleeve's GPS firmware sometimes puts the direction in
# the wrong order.
if not words[0] or not words[1] or not words[2] or not words[3]:
return False
if words[0][-1] == 'N':
words[0] = words[0][:-1]
words[1] = 'N'
if words[0][-1] == 'S':
words[0] = words[0][:-1]
words[1] = 'S'
if words[2][-1] == 'E':
words[2] = words[2][:-1]
words[3] = 'E'
if words[2][-1] == 'W':
words[2] = words[2][:-1]
words[3] = 'W'
if len(words[0]):
lat = float(words[0])
frac, intpart = math.modf(lat / 100.0)
lat = intpart + frac * 100.0 / 60.0
if words[1] == 'S':
lat = -lat
if len(words[2]):
lon = float(words[2])
frac, intpart = math.modf(lon / 100.0)
lon = intpart + frac * 100.0 / 60.0
if words[3] == 'W':
lon = -lon
self.data.latlon_stamp.refresh()
self.data.latlon_stamp.changed = ((lat, lon) != (self.data.latitude, self.data.longitude))
self.data.latitude = lat
self.data.longitude = lon
return True
# Three sentences, GGA and GGL and RMC, contain timestamps.
# Timestamps always look like hhmmss.ss, with the trailing .ss
# part optional. RMC alone has a date field, in the format
# ddmmyy.
#
# We want the output to be in ISO 8601 format:
#
# yyyy-mm-ddThh:mm:ss.sssZ
# 012345678901234567890123
#
# (where part or all of the decimal second suffix may be omitted).
# This means that for GPRMC we must supply a century and for GGA and
# GGL we must supply a century, year, and day.
#
# We get the missing data from the host machine's clock time. That
# is, the machine where this *daemon* is running -- which is probably
# connected to the GPS by a link short enough that it doesn't cross
# the International Date Line. Even if it does, this hack could only
# screw the year number up for two hours around the first midnight of
# a new century.
def update_timestamp(self, ddmmyy=None, hhmmss=None):
if not ddmmyy:
yyyymmdd = time.strftime("%Y-%m-%d")
else:
yyyymmdd = time.strftime("%C") + "%s-%s-%s" % (ddmmyy[4:6], ddmmyy[2:4], ddmmyy[0:2])
if not hhmmss:
hhmmss = time.strftime("%H:%M:%S")
else:
hhmmss = hhmmss[0:2] + ":" + hhmmss[2:4] + ":" + hhmmss[4:]
self.data.utc = yyyymmdd + "T" + hhmmss + "Z"
def processGPRMC(self, words):
if words[1] == "A":
self.update_timestamp(words[8], words[0])
if self.__do_lat_lon(words[2:]):
if words[6]:
newspeed = float(words[6])
self.data.speed_stamp.changed = (self.data.speed != newspeed)
self.data.speed = newspeed
self.data.speed_stamp.refresh()
if words[7]:
newtrack = float(words[7])
self.data.track_stamp.changed = (self.data.track != newtrack)
self.data.track = newtrack
self.data.track_stamp.refresh()
def processGPGLL(self, words):
if words[1] == "A":
self.__do_lat_lon(words)
self.update_timestamp(None, words[4])
if words[5] == 'N':
newstatus = gps.STATUS_NO_FIX
elif words[5] == 'D':
newstatus = gps.STATUS_DGPS_FIX
else:
newstatus = gps.STATUS_FIX;
self.data.status_stamp.changed = (self.data.status != newstatus)
self.data.status = newstatus
self.logger(3, "GPGLL sets status %d\n", self.data.status);
def processGPGGA(self,words):
self.update_timestamp(None, words[0])
self.__do_lat_lon(words[1:])
if words[8]:
newaltitude = float(words[8])
self.data.altitude_stamp.changed = (self.data.altitude != newaltitude)
self.data.altitude = newaltitude
self.data.altitude_stamp.refresh()
if words[5]:
newstatus = int(words[5])
self.data.status_stamp.changed = (self.data.status != newstatus)
self.data.status = newstatus
self.data.status_stamp.refresh()
self.logger(3, "GPGGA sets status %d\n" % self.data.status);
def processGPGSA(self,words):
newmode = int(words[1])
self.data.mode_stamp.changed = (self.data.mode != newmode)
self.data.mode = newmode
self.data.mode_stamp.refresh()
self.data.satellites_used = map(int, filter(lambda x: x, words[2:14]))
(newpdop, newhdop, newvdop) = (self.data.pdop, self.data.hdop, self.data.vdop)
if words[14]:
newpdop = float(words[14])
if words[15]:
newhdop = float(words[15])
if words[16]:
newvdop = float(words[16])
if words[14] and words[15] and words[16]:
self.data.fix_quality_stamp.refresh()
self.data.fix_quality_stamp.changed = (newpdop, newhdop, newvdop) != (self.data.pdop, self.data.hdop, self.data.vdop)
(self.data.pdop, self.data.hdop, self.data.vdop) = (newpdop, newhdop, newvdop)
self.logger(3, "GPGGA sets mode %d\n" % self.data.mode)
def processGPGVTG(self, words):
if words[0]:
newtrack = float(words[0])
self.data.track_stamp.changed = (self.data.track != newtrack)
self.data.track = newtrack
self.data.track_stamp.refresh()
if words[1] == 'T':
newspeed = words[4]
else:
newspeed = words[2]
if newspeed:
newspeed = float(newspeed)
self.data.speed_stamp.changed = (self.data.speed != newspeed)
self.data.speed = newspeed
def nmea_sane_satellites(self):
# data may be incomplete *
if self.data.part < self.data.await:
return False;
# This sanity check catches an odd behavior of the BU-303, and thus
# possibly of other SiRF-II based GPSes. When they can't see any
# satellites at all (like, inside a building) they sometimes cough
# up a hairball in the form of a GSV packet with all the azimuth
# and entries 0 (but nonzero elevations). This
# was observed under SiRF firmware revision 231.000.000_A2.
for sat in self.data.satellites:
if sat.azimuth[n]:
return True;
return False;
def processGPGSV(self, words):
self.data.await = int(words.pop(0))
self.data.part = int(words.pop(0))
inview = int(words.pop(0)) # Total satellites in view
lower = (self.data.part - 1) * 4
upper = lower + 4
fldnum = 0
newsats = []
while lower < inview and lower < upper:
prn = int(words[fldnum]); fldnum += 1
elevation = int(words[fldnum]); fldnum += 1
azimuth = int(words[fldnum]); fldnum += 1
if words[fldnum]:
ss = int(words[fldnum])
else:
ss = gps.SIGNAL_STRENGTH_UNKNOWN
fldnum += 1
newsats.append(gps.gpsdata.satellite(prn, elevation, azimuth, ss))
lower += 1
# not valid data until we've seen a complete set of parts
if self.data.part < self.data.await:
self.logger(3, "Partial satellite data (%d of %d).\n" % (self.data.part, self.data.await));
else:
# trim off PRNs with spurious data attached
while newsats \
and not newsats[-1].elevation \
and not newsats[-1].azimuth \
and not newsats[-1].ss:
newsats.pop()
if self.nmea_sane_satellites():
self.data.satellites = newsats
self.logger(3, "Satellite data OK.\n")
else:
self.logger(3, "Satellite data no good.\n");
def handle_line(self, line):
if line and line[0] == '$':
line = line[1:].split('*')
if len(line) != 2: return
if not self.checksum(line[0], line[1]):
self.logger(0, "Bad checksum\n")
return
words = line[0].split(',')
if NMEA.__dict__.has_key('process'+words[0]):
NMEA.__dict__['process'+words[0]](self, words[1:])
else:
self.logger(0, "Unknown sentence\n")
else:
return self.logger(0, "Not NMEA\n")
def handler(self, fp, raw_hook):
linebuf = fp.readline()
self.handle_line(linebuf[:-2])
if raw_hook:
raw_hook(linebuf)
class gpsd(gps.gpsdata):
"Device interface to a GPS."
class gps_driver:
def __init__(self, name,
parser=NMEA,
cycle=1, bps=4800, stopbits=1,
trigger=None, initializer=None, rtcm=None, wrapup=None):
self.name = name
self.parser = parser
self.cycle = cycle
self.bps = bps
self.stopbits = stopbits
self.trigger = trigger
self.initializer = initializer
self.rtcm = rtcm
self.wrap = wrapup
def __init__(self, device="/dev/gps", bps=4800,
devtype='n', dgps=None, logger=None):
self.ttyfp = None
self.device = device
self.bps = bps
self.drivers = {
'n' : gpsd.gps_driver("NMEA"),
'f' : gpsd.gps_driver("NMEA", stopbits=2,
initializer = lambda gps: gps.send("$PFEC,GPint,GSA01,DTM00,ZDA00,RMC01,GLL01")),
# Someday, other drivers go here
}
self.devtype = self.drivers[devtype]
if not logger:
logger = lambda level, message: None
self.devtype.parser = self.devtype.parser(self, logger=logger)
self.logger = logger
self.dsock = -1
self.fixcnt = 0
self.sentdgps = 0
gps.gpsdata.__init__(self)
if dgps:
dgpsport = "2101"
if ":" in dgps:
(dgps, dgpsport) = dgps(":")
self.dsock = gps.gps.connect(self, dgps, dgpsport)
self.raw_hook = None
def __del__(self):
self.deactivate()
if self.dsock >= 0:
os.close(self.dsock);
close = __del__
def send(self, buf):
self.ttyfp.write(self.parser.add_checksum(buf))
def activate(self):
self.ttyfp = open(self.device, "rw")
if self.ttyfp == None:
return None
self.normal = termios.tcgetattr(self.ttyfp.fileno())
self.raw = termios.tcgetattr(self.ttyfp.fileno())
self.raw[0] = 0 # iflag
self.raw[1] = termios.ONLCR # oflag
# Tip from Chris Kuethe: the FIDI chip used in the Trip-Nav
# 200 (and possibly other USB GPSes) gets completely hosed
# in the presence of flow control. Thus, turn off CRTSCTS.
self.raw[2] &= ~(termios.PARENB | termios.CRTSCTS) # cflag
if self.devtype.stopbits == 2:
self.raw[2] |= (termios.CSIZE & termios.CS7) # cflag
else:
self.raw[2] |= (termios.CSIZE & termios.CS8) # cflag
self.raw[2] |= termios.CREAD | termios.CLOCAL # cflag
self.raw[3] = 0 # lflag
self.raw[4] = self.raw[5] = eval("termios.B" + `self.bps`)
termios.tcsetattr(self.ttyfp.fileno(), termios.TCSANOW, self.raw)
termios.tcflush(self.ttyfp.fileno(), termios.TCIOFLUSH)
time.sleep(1.25)
if self.devtype.initializer:
self.devtype.initializer(self)
self.online = True;
return self.ttyfp
def deactivate(self):
if hasattr(self, 'normal'):
termios.tcsetattr(self.ttyfp.fileno(), termios.TCSANOW, self.normal)
self.online = False;
self.mode = gps.MODE_NO_FIX;
self.status = gps.STATUS_NO_FIX;
def set_raw_hook(self, hook=None):
self.raw_hook = hook
def waiting(self):
"How much input is waiting?"
if self.ttyfp == None:
return -1
st = fcntl.ioctl(self.ttyfp.fileno(), termios.FIONREAD, " "*struct.calcsize('i'))
if st == -1:
return -1
st = struct.unpack('i', st)[0]
return st
def rawread(self):
ready = self.waiting()
if ready:
return self.ttyfp.read(ready)
else:
return None
def rawwrite(self, buf):
return self.ttyfp.write(buf)
def poll(self):
if self.dsock > -1:
self.ttyfp.write(session.dsock.recv(1024))
waiting = self.waiting()
if waiting < 0:
return waiting
elif waiting == 0:
if time.time() < self.online_stamp.last_refresh + self.devtype.cycle + 1:
return 0
else:
self.online = False
self.online_stamp.refresh()
return -1
else:
self.online = True
self.online_stamp.refresh()
self.devtype.parser.handler(self.ttyfp, self.raw_hook)
# count the good fixes
if self.status > gps.STATUS_NO_FIX:
self.fixcnt += 1;
# may be time to ship a DGPS correction to the GPS
if self.fixcnt > 10:
if not self.sentdgps:
self.sentdgps += 1;
if self.dsock > -1:
self.dsock.send(self.dsock, \
"R %0.8f %0.8f %0.2f\r\n" % \
(self.latitude, self.longitude, self.altitude))
return waiting;
# SirF-II control code
class SiRF:
def transport(payload):
msg = '\xa0'
msg += '\xa2'
msg += chr(len(payload) >> 8)
msg += chr(len(payload) & 0xff)
msg += payload
checksum = 0
for ch in payload:
checksum += ord(ch);
checksum &= 0x7fff
msg += chr((checksum >> 8) & 0xff00)
msg += chr(checksum & 0x00ff)
msg += '\xb0'
msg += '\xb3'
return msg
transport = staticmethod(transport)
def to_NMEA(baudrate):
"Generate a SiRF binary protocol command to switch back to NMEA."
switcher = [
'\x81', # Byte 0 = 0x81: Switch to NMEA command
'\x02', # Byte 1 = 0x02: Leave debug-message switch as it is.
'\x01', # Byte 2 = 0x01: Enable GPGGA at 1-second interval
'\x01', # Byte 3 = 0x01: GPGGA checksum enable
'\x01', # Byte 4 = 0x01: Enable GPGLL at 1-second interval
'\x01', # Byte 5 = 0x01: GPGLL checksum enable
'\x01', # Byte 6 = 0x05: Enable GPGSA at 5-second interval
'\x01', # Byte 7 = 0x01: GPGSA checksum enable
'\x05', # Byte 8 = 0x05: Enable GPGSV at 5-second interval
'\x01', # Byte 9 = 0x01: GPGSV checksum enable
'\x00', # Byte 10 = 0x05: Disable GPMSS
'\x00', # Byte 11 = 0x01: GPMSS checksum disable
'\x01', # Byte 12 = 0x01: Enable GPRMC at 1-second interval
'\x01', # Byte 13 = 0x01: GPRMC checksum enable
'\x01', # Byte 14 = 0x01: Enable GPVTG at 1-second interval
'\x01', # Byte 15 = 0x01: GPVTG checksum enable
'\x00', # Byte 16 = 0x00: Unused
'\x00', # Byte 17 = 0x00: Unused
'\x00', # Byte 18 = 0x00: Unused
'\x00', # Byte 19 = 0x00: Unused
'\x00', # Byte 20 = 0x00: Unused
'\x00', # Byte 21 = 0x00: Unused
]
switcher += [chr(baudrate >> 8), chr(baudrate & 0x0ff)]
return SiRF.transport("".join(switcher))
to_NMEA = staticmethod(to_NMEA)
def reset():
"Generate a GPS reset command."
return SiRF.transport("\x85\x00\x00\x00\x00\x00\x00\x00\x00")
reset = staticmethod(reset)
if __name__ == '__main__':
import sys
def logger(level, message):
sys.stdout.write(message)
def dumpline(message):
sys.stdout.write("Raw line: " + `message`+ "\n")
dev = gpsd(logger=logger)
dev.set_raw_hook(dumpline)
dev.activate()
while True:
status = dev.poll()
if status > 0:
print dev
print "=" * 75
del dev
|