×
Namespaces

Variants
Actions
(Difference between revisions)

Archived:NMEA (GPS) Location Viewer

From Nokia Developer Wiki
Jump to: navigation, search
cjmartin (Talk | contribs)
(New page: Category:S60Category:PythonCategory:Code Examples Good starter code for working with GPS data: Connects to a bluetooth GPS receiver and parses the NMEA sentence, printing the...)
 
jaaura (Talk | contribs)
m
Line 1: Line 1:
[[Category:S60]][[Category:Python]][[Category:Code Examples]]
+
[[Category:S60]][[Category:Python]][[Category:Code Examples]][[Category:Location Based Services]]
  
 
Good starter code for working with GPS data:
 
Good starter code for working with GPS data:

Revision as of 17:42, 7 March 2008


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 0 to request a quit
going = 1
 
#############################################################################
 
# 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 = csum ^ ord(c)
hex_csum = "%02x" % csum
return hex_csum.upper()
 
# 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 1:
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 = 0
appuifw.app.exit_key_handler = None
 
#############################################################################
 
# Get the location from a GGA sentence
def get_gga_location(data):
d = data.split(',')
ret = {}
ret['type'] = 'GGA'
ret['lat'] = "%s%s" % (d[1],d[2])
ret['long'] = "%s%s" % (d[3],d[4])
ret['time'] = format_time(d[0])
return ret
 
# Get the location from a GLL sentence
def get_gll_location(data):
d = data.split(',')
ret = {}
ret['type'] = 'GLL'
ret['lat'] = "%s%s" % (d[0],d[1])
ret['long'] = "%s%s" % (d[2],d[3])
ret['time'] = format_time(d[4])
return ret
 
# Get the location from a RMC sentence
def get_rmc_location(data):
d = data.split(',')
ret = {}
ret['type'] = 'RMC'
ret['lat'] = "%s%s" % (d[2],d[3])
ret['long'] = "%s%s" % (d[4],d[5])
ret['time'] = format_time(d[0])
return ret
 
#############################################################################
 
# Loop while active
appuifw.app.exit_key_handler = exit_key_pressed
while going == 1:
rawdata = readline(sock)
if not rawdata: break
data = rawdata.strip()
 
# Ensure it starts with $GP
if not data[0:3] == '$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 not 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 = gga_log_count + 1
if gga_log_count == gga_log_interval:
gga_log_count = 0
gga_log_fh.write(rawdata)
if sentence_id == 'GLL':
location = get_gll_location(sentence_data)
if sentence_id == 'RMC':
location = get_rmc_location(sentence_data)
 
# If we got a location, print it
if not 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()
80 page views in the last 30 days.