platypush/platypush/backend/gps.py

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import threading
import time
from platypush.backend import Backend
from platypush.message.event.gps import GPSVersionEvent, GPSDeviceEvent, GPSUpdateEvent
class GpsBackend(Backend):
"""
This backend can interact with a GPS device and listen for events.
Triggers:
* :class:`platypush.message.event.gps.GPSVersionEvent` when a GPS device advertises its version data
* :class:`platypush.message.event.gps.GPSDeviceEvent` when a GPS device is connected or updated
* :class:`platypush.message.event.gps.GPSUpdateEvent` when a GPS device has new data
Requires:
* **gps** (``pip install gps``)
* **gpsd** daemon running (``apt-get install gpsd`` or ``pacman -S gpsd`` depending on your distro)
Once installed gpsd you need to run it and associate it to your device. Example if your GPS device communicates
over USB and is available on /dev/ttyUSB0::
[sudo] gpsd /dev/ttyUSB0 -F /var/run/gpsd.sock
The best option is probably to run gpsd at startup as a systemd service.
"""
_fail_sleep_time = 5.0
_lat_lng_tolerance = 1e-5
_alt_tolerance = 0.5
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def __init__(self, gpsd_server='localhost', gpsd_port=2947, **kwargs):
"""
:param gpsd_server: gpsd daemon server name/address (default: localhost)
:type gpsd_server: str
:param gpsd_port: Port of the gpsd daemon (default: 2947)
:type gpsd_port: int or str
"""
super().__init__(**kwargs)
self.gpsd_server = gpsd_server
self.gpsd_port = gpsd_port
self._session = None
self._session_lock = threading.RLock()
self._devices = {}
def _get_session(self):
import gps
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with self._session_lock:
if not self._session:
self._session = gps.gps(host=self.gpsd_server, port=self.gpsd_port, reconnect=True)
self._session.stream(gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)
return self._session
def _gps_report_to_event(self, report):
if report.get('class').lower() == 'version':
return GPSVersionEvent(release=report.get('release'),
rev=report.get('rev'),
proto_major=report.get('proto_major'),
proto_minor=report.get('proto_minor'))
if report.get('class').lower() == 'devices':
for device in report.get('devices', []):
if device.get('path') not in self._devices or device != self._devices.get('path'):
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# noinspection DuplicatedCode
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self._devices[device.get('path')] = device
return GPSDeviceEvent(path=device.get('path'), activated=device.get('activated'),
native=device.get('native'), bps=device.get('bps'),
parity=device.get('parity'), stopbits=device.get('stopbits'),
cycle=device.get('cycle'), driver=device.get('driver'))
if report.get('class').lower() == 'device':
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# noinspection DuplicatedCode
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self._devices[report.get('path')] = report
return GPSDeviceEvent(path=report.get('path'), activated=report.get('activated'),
native=report.get('native'), bps=report.get('bps'),
parity=report.get('parity'), stopbits=report.get('stopbits'),
cycle=report.get('cycle'), driver=report.get('driver'))
if report.get('class').lower() == 'tpv':
return GPSUpdateEvent(device=report.get('device'), latitude=report.get('lat'), longitude=report.get('lon'),
altitude=report.get('alt'), mode=report.get('mode'), epv=report.get('epv'),
eph=report.get('eph'), sep=report.get('sep'))
def run(self):
super().run()
self.logger.info('Initialized GPS backend on {}:{}'.format(self.gpsd_server, self.gpsd_port))
last_event = None
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while not self.should_stop():
try:
session = self._get_session()
report = session.next()
event = self._gps_report_to_event(report)
if event and (last_event is None or
abs((last_event.args.get('latitude') or 0) - (event.args.get('latitude') or 0)) >= self._lat_lng_tolerance or
abs((last_event.args.get('longitude') or 0) - (event.args.get('longitude') or 0)) >= self._lat_lng_tolerance or
abs((last_event.args.get('altitude') or 0) - (event.args.get('altitude') or 0)) >= self._alt_tolerance):
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self.bus.post(event)
last_event = event
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except Exception as e:
if isinstance(e, StopIteration):
self.logger.warning('GPS service connection lost, check that gpsd is running')
else:
self.logger.exception(e)
self._session = None
time.sleep(self._fail_sleep_time)
# vim:sw=4:ts=4:et: