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#!/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 = (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:])
self.data.status = int(words[5])
self.data.altitude = float(words[8])
self.logger(3, "GPGGA sets status %d\n" % self.data.status);
def processGPGSA(self,words):
self.data.mode = int(words[1])
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):
self.data.track = float(words[0])
if words[1] == 'T':
newspeed = float(words[4])
self.data.speed_stamp.changed = (self.data.speed != newspeed)
self.data.speed = newspeed
else:
newtrack = float(words[2])
self.data.track_stamp.changed = (self.data.track != newtrack)
self.data.track = newtrack
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
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)
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 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;
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
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