为了保留一个老问题，下面粘贴的是GPS3, a Python 2.7-3.5 gpsd client 的当前状态https://github.com/wadda/gps3。
GPS3 有两个组件； GPSDSocket 类和 Fix 类。
GPSD 在许多“类”、TPV、SKY 等中提供 JSON 数据。连接到 GPSD 后，GPS3 将这些 JSON 对象解包到字典中（Fix.TPV['lat']、Fix.SKY['satellites'] 等）
通常会创建一个实例，例如fix = gps3.Fix()，所有可用的数据都将派生自本机 JSON 对象的名称（例如，fix.TPV['speed']、fix.TPV['alt'] 等）
使用a demo application gegps3.py 来创建一个kml 文件(/tmp/gps3_live.kml)，以便在Google 地球中查看。
#!/usr/bin/env python3
# coding=utf-8
"""
GPS3 (gps3.py) is a Python 2.7-3.5 GPSD interface (http://www.catb.org/gpsd)
Defaults host='127.0.0.1', port=2947, gpsd_protocol='json'
GPS3 has two classes.
1) 'GPSDSocket' to create a GPSD socket connection and request/retreive GPSD output.
2) 'Fix' unpacks the streamed gpsd data into python dictionaries.
These dictionaries are literated from the JSON data packet sent from the GPSD.
Import import gps3
Instantiate gps_connection = gps3.GPSDSocket(host='192.168.0.4')
gps_fix = gps3.Fix()
Iterate for new_data in gps_connection:
if new_data:
gps_fix.refresh(new_data)
Use print('Altitude = ',gps_fix.TPV['alt'])
print('Latitude = ',gps_fix.TPV['lat'])
Consult Lines 152-ff for Attribute/Key possibilities.
or http://www.catb.org/gpsd/gpsd_json.html
Run human.py; python[X] human.py [arguments] for a human experience.
"""
from __future__ import print_function
import json
import select
import socket
import sys
__author__ = 'Moe'
__copyright__ = 'Copyright 2015-2016 Moe'
__license__ = 'MIT'
__version__ = '0.2'
HOST = '127.0.0.1' # gpsd
GPSD_PORT = 2947 # defaults
PROTOCOL = 'json' # "
class GPSDSocket(object):
"""Establish a socket with gpsd, by which to send commands and receive data."""
def __init__(self, host=HOST, port=GPSD_PORT, gpsd_protocol=PROTOCOL, devicepath=None):
self.devicepath_alternate = devicepath
self.response = None
self.protocol = gpsd_protocol
self.streamSock = None
if host:
self.connect(host, port)
def connect(self, host, port):
"""Connect to a host on a given port.
Arguments:
port: default port=2947
host: default host='127.0.0.1'
"""
for alotta_stuff in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
family, socktype, proto, _canonname, host_port = alotta_stuff
try:
self.streamSock = socket.socket(family, socktype, proto)
self.streamSock.connect(host_port)
self.streamSock.setblocking(False)
self.watch(gpsd_protocol=self.protocol)
except OSError as error:
sys.stderr.write('\nGPSDSocket.connect OSError is-->', error)
sys.stderr.write('\nAttempt to connect to a gpsd at {0} on port \'{1}\' failed:\n'.format(host, port))
sys.exit(1) # TODO: gpsd existence check and start
def watch(self, enable=True, gpsd_protocol='json', devicepath=None):
"""watch gpsd in various gpsd_protocols or devices.
Arguments:
self:
enable: (bool) stream data to socket
gpsd_protocol: (str) 'json' | 'nmea' | 'rare' | 'raw' | 'scaled' | 'split24' | 'pps'
devicepath: (str) device path - '/dev/ttyUSBn' for some number n or '/dev/whatever_works'
Returns:
command: (str) e.g., '?WATCH={"enable":true,"json":true};'
"""
# N.B.: 'timing' requires special attention, as it is undocumented and lives with dragons.
command = '?WATCH={{"enable":true,"{0}":true}}'.format(gpsd_protocol)
if gpsd_protocol == 'rare': # 1 for a channel, gpsd reports the unprocessed NMEA or AIVDM data stream
command = command.replace('"rare":true', '"raw":1')
if gpsd_protocol == 'raw': # 2 channel that processes binary data, received data verbatim without hex-dumping.
command = command.replace('"raw":true', '"raw",2')
if not enable:
command = command.replace('true', 'false') # sets -all- command values false .
if devicepath:
command = command.replace('}', ',"device":"') + devicepath + '"}'
return self.send(command)
def send(self, commands):
"""Ship commands to the daemon
Arguments:
commands: e.g., '?WATCH={{'enable':true,'json':true}}'|'?VERSION;'|'?DEVICES;'|'?DEVICE;'|'?POLL;'
"""
# The POLL command requests data from the last-seen fixes on all active GPS devices.
# Devices must previously have been activated by ?WATCH to be pollable.
if sys.version_info[0] < 3: # Not less than 3, but 'broken hearted' because
self.streamSock.send(commands) # 2.7 chokes on 'bytes' and 'encoding='
else:
self.streamSock.send(bytes(commands, encoding='utf-8')) # It craps out here when there is no gpsd running
# TODO: Add recovery, check gpsd existence, re/start, etc..
def __iter__(self):
"""banana""" # <------- for scale
return self
def next(self, timeout=0):
"""Return empty unless new data is ready for the client.
Arguments:
timeout: Default timeout=0 range zero to float specifies a time-out as a floating point
number in seconds. Will sit and wait for timeout seconds. When the timeout argument is omitted
the function blocks until at least one file descriptor is ready. A time-out value of zero specifies
a poll and never blocks.
"""
try:
waitin, _waitout, _waiterror = select.select((self.streamSock,), (), (), timeout)
if not waitin: return
else:
gpsd_response = self.streamSock.makefile() # '.makefile(buffering=4096)' In strictly Python3
self.response = gpsd_response.readline()
return self.response
except OSError as error:
sys.stderr.write('The readline OSError in GPSDSocket.next is this: ', error)
__next__ = next # Workaround for changes in iterating between Python 2.7 and 3
def close(self):
"""turn off stream and close socket"""
if self.streamSock:
self.watch(enable=False)
self.streamSock.close()
self.streamSock = None
class Fix(object):
"""Retrieve JSON Object(s) from GPSDSocket and unpack it into respective
gpsd 'class' dictionaries, TPV, SKY, etc. yielding hours of fun and entertainment.
"""
def __init__(self):
"""Potential data packages from gpsd for a generator of class attribute dictionaries"""
packages = {'VERSION': {'release', 'proto_major', 'proto_minor', 'remote', 'rev'},
'TPV': {'alt', 'climb', 'device', 'epc', 'epd', 'eps', 'ept', 'epv', 'epx', 'epy', 'lat', 'lon', 'mode', 'speed', 'tag', 'time', 'track'},
'SKY': {'satellites', 'gdop', 'hdop', 'pdop', 'tdop', 'vdop', 'xdop', 'ydop'},
# Subset of SKY: 'satellites': {'PRN', 'ss', 'el', 'az', 'used'} # is always present.
'GST': {'alt', 'device', 'lat', 'lon', 'major', 'minor', 'orient', 'rms', 'time'},
'ATT': {'acc_len', 'acc_x', 'acc_y', 'acc_z', 'depth', 'device', 'dip', 'gyro_x', 'gyro_y', 'heading', 'mag_len', 'mag_st', 'mag_x',
'mag_y', 'mag_z', 'pitch', 'pitch_st', 'roll', 'roll_st', 'temperature', 'time', 'yaw', 'yaw_st'},
# 'POLL': {'active', 'tpv', 'sky', 'time'},
'PPS': {'device', 'clock_sec', 'clock_nsec', 'real_sec', 'real_nsec', 'precision'},
'TOFF': {'device', 'clock_sec', 'clock_nsec','real_sec', 'real_nsec' },
'DEVICES': {'devices', 'remote'},
'DEVICE': {'activated', 'bps', 'cycle', 'mincycle', 'driver', 'flags', 'native', 'parity', 'path', 'stopbits', 'subtype'},
# 'AIS': {} # see: http://catb.org/gpsd/AIVDM.html
'ERROR': {'message'}} # TODO: Full suite of possible GPSD output
for package_name, dataset in packages.items():
_emptydict = {key: 'n/a' for key in dataset}
setattr(self, package_name, _emptydict)
self.DEVICES['devices'] = {key: 'n/a' for key in packages['DEVICE']} # How does multiple listed devices work?
# self.POLL = {'tpv': self.TPV, 'sky': self.SKY, 'time': 'n/a', 'active': 'n/a'}
def refresh(self, gpsd_data_package):
"""Sets new socket data as Fix attributes in those initialied dictionaries
Arguments:
self:
gpsd_data_package (json object):
Provides:
self attribute dictionaries, e.g., self.TPV['lat'], self.SKY['gdop']
Raises:
AttributeError: 'str' object has no attribute 'keys' when the device falls out of the system
ValueError, KeyError: most likely extra, or mangled JSON data, should not happen, but that
applies to a lot of things.
"""
try:
fresh_data = json.loads(gpsd_data_package) # The reserved word 'class' is popped from JSON object class
package_name = fresh_data.pop('class', 'ERROR') # gpsd data package errors are also 'ERROR'.
package = getattr(self, package_name, package_name) # packages are named for JSON object class
for key in package.keys(): # TODO: Rollover and retry. It fails here when device disappears
package[key] = fresh_data.get(key, 'n/a') # Updates and restores 'n/a' if key is absent in the socket
# response, present --> 'key: 'n/a'' instead.'
except AttributeError: # 'str' object has no attribute 'keys'
print('No Data')
return
except (ValueError, KeyError) as error:
sys.stderr.write(str(error)) # Look for extra data in stream
return
if __name__ == '__main__':
print('\n', __doc__)
#
# Someday a cleaner Python interface will live here
#
# End