×
Namespaces

Variants
Actions

Archived:NMEA (GPS) Location Viewer

From Nokia Developer Wiki
Jump to: navigation, search

Archived.pngAquivado: Este artigo foi arquivado, pois o conteúdo não é mais considerado relevante para se criar soluções comerciais atuais. Se você achar que este artigo ainda é importante, inclua o template {{ForArchiveReview|escreva a sua justificativa}}.

All PySymbian articles have been archived. PySymbian is no longer maintained by Nokia and is not guaranteed to work on more recent Symbian devices. It is not possible to submit apps to Nokia Store.

Article Metadata
Article
Created: cjmartin (29 Mar 2007)
Last edited: hamishwillee (31 May 2013)

Good starter code for working with GPS data:

Connects to a bluetooth GPS receiver and parses the NMEA sentence, printing the location to the screen.

From Nick's Code - check there for any updates.

# Basic script to grab the current location from an NMEA bluetooth GPS,
# and log it to the screen
# Also optionally logs periodic location data to a file, so you can see
# where you were
#
# GPL
#
# Nick Burch - v0.01 (15/01/2006)
 
import appuifw
import socket
 
# Bluetooth address to connect to
# Change this to your GPS's bluetooth address!
gps_addr='00:15:4B:01:14:EE'
 
# How many GGA sentences between logging
# Set to 0 to prevent logging
gga_log_interval = 10
gga_log_count = 0
 
# File to log GGA sentences into
gga_log_file = 'e:\\nmea_gga_log.txt'
 
# We want icons etc
appuifw.app.screen='normal'
 
# Define title etc
appuifw.app.title=u"NMEA Location Disp"
 
# Alert them to the GPS we're going to connect to
appuifw.note(u"Will connect to GPS %s" % gps_addr, 'info')
 
# Connect to the bluetooth GPS using the serial service
sock=socket.socket(socket.AF_BT, socket.SOCK_STREAM)
target=(gps_addr,1)
sock.connect(target)
 
appuifw.note(u"Connected to the GPS")
 
# Open the GGA log file, in append mode
gga_log_fh = open(gga_log_file,'a');
 
# This is set to False to request a quit
going = True
 
#############################################################################
 
# Generate the checksum for some data
# (Checksum is all the data XOR'd, then turned into hex)
def generate_checksum(data):
csum = 0
for c in data:
csum ^= ord(c)
hex_csum = "%02X" % csum
return hex_csum
 
# Format a NMEA timestamp into something friendly
def format_time(time):
hh = time[0:2]
mm = time[2:4]
ss = time[4:]
return "%s:%s:%s UTC" % (hh,mm,ss)
 
# Format a NMEA date into something friendly
def format_date(date):
months = ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec')
dd = date[0:2]
mm = date[2:4]
yy = date[4:6]
yyyy = int(yy) + 2000
return "%s %s %d" % (dd, months[int(mm)-1], yyyy)
 
#############################################################################
 
def readline(sock):
"""Read one single line from the socket"""
line = ""
while True:
char = sock.recv(1)
if not char: break
line += char
if char == "\n": break
return line
 
def exit_key_pressed():
"""Function called when the user requests exit"""
# TODO Figure out why going in the main thread isn't updated
going = False
appuifw.app.exit_key_handler = None
 
#############################################################################
 
# Get the location from a GGA sentence
def get_gga_location(data):
d = data.split(',')
return {
'type': 'GGA',
'lat': "%s%s" % (d[1],d[2]),
'long': "%s%s" % (d[3],d[4]),
'time': format_time(d[0])
}
 
# Get the location from a GLL sentence
def get_gll_location(data):
d = data.split(',')
return {
'type': 'GLL',
'lat': "%s%s" % (d[0],d[1]),
'long': "%s%s" % (d[2],d[3]),
'time': format_time(d[4])
}
 
# Get the location from a RMC sentence
def get_rmc_location(data):
d = data.split(',')
return {
'type': 'RMC',
'lat': "%s%s" % (d[2],d[3]),
'long': "%s%s" % (d[4],d[5]),
'time': format_time(d[0])
}
 
#############################################################################
 
# Loop while active
appuifw.app.exit_key_handler = exit_key_pressed
while going:
rawdata = readline(sock)
if not rawdata: break
data = rawdata.strip()
 
# Ensure it starts with $GP
if not data.startswith('$GP'):
continue
 
# If it has a checksum, ensure that's correct
# (Checksum follows *, and is XOR of everything from
# the $ to the *, exclusive)
if data[-3] == '*':
exp_checksum = generate_checksum(data[1:-3])
if exp_checksum != data[-2:]:
print "Invalid checksum %s, expecting %s" % (data[-2:], exp_checksum)
continue
 
# Strip the checksum
data = data[:-3]
 
# Grab the parts of the sentence
talker = data[1:3]
sentence_id = data[3:6]
sentence_data = data[7:]
 
# The NMEA sentences we're interested in are:
# GGA - Global Positioning System Fix Data
# GLL - Geographic Position
# RMC - GPS Transit Data
location = {}
if sentence_id == 'GGA':
location = get_gga_location(sentence_data)
 
# Log GGA packets periodically
gga_log_count += 1
if gga_log_count == gga_log_interval:
gga_log_count = 0
gga_log_fh.write(rawdata)
elif sentence_id == 'GLL':
location = get_gll_location(sentence_data)
elif sentence_id == 'RMC':
location = get_rmc_location(sentence_data)
 
# If we got a location, print it
if location != {}:
# Check the location is valid
if location['lat'] == '0000.0000N' and location['long'] == '0000.0000E':
print "Invalid GPS location found"
else:
print "Source of location is %s" % location['type']
print "Lat is %s" % location['lat']
print "Long is %s" % location['long']
print "Time is %s" % location['time']
print ""
 
# Future:
# Grab satellites in view from GSV
# Grab satellites in use from GSA
# Grab speed and direction from VTG
 
# For debugging
#print data
 
# All done
sock.close()
gga_log_fh.close()
 
print "All done"
appuifw.app.set_exit()
This page was last modified on 31 May 2013, at 04:05.
91 page views in the last 30 days.
×