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mjuenema / python-gpsdshm

Python interface to gpsd's shared memory segment.
BSD 2-Clause "Simplified" License
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python-gpsdshm

Overview

python-gpsdshm provides a read-only(!) Python interface to gpsd_'s shared memory. It provides a single class Shm that exposes the fields of the shared memory structure as attributes. The python-gpsdshm API is (loosely) modelled on gpsd version 3.16 (API 6.1). gpsd releases earlier than 3.0 are not supported.

python-gpsdshm is implemented using Swig and requires the gpsd header files for compilation. Please note that some Linux distributions contain Swig releases that are too old for working with Python 3.

Many Linux distributions ship the gpsd package without shared memory support. See Compiling gpsd with shared memory support_ for details how to build gpsd with shared memory support.

Status

python-gpsdshm is automatically tested against the following Python versions:

+--------------+-------------------+-------------------+--------------------+--------------------+ | Branch | Travis-CI | Codecov | Codacy | Landscape | +==============+===================+===================+====================+====================+ | master | |traviscimaster| | |codecovmaster| | |codacymaster| | |landscapemaster| | +--------------+-------------------+-------------------+--------------------+--------------------+ | develop | |traviscidevelop| | |codecovdevelop| | |codacydevelop| | |landscapedevelop| | +--------------+-------------------+-------------------+--------------------+--------------------+

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.. _python-gpsdshm Travis-CI page: https://travis-ci.org/mjuenema/python-gpsdshm

.. _gpsd: http://www.catb.org/gpsd/ .. _Swig: http://www.swig.org/Doc1.3/Python.html

Example

The gpsdshm.Shm class provides the interface to gpsd's shared memory.

.. code-block:: python

import gpsdshm gpsd_shm = gpsdshm.Shm() gpsd_shm.online # Timestamp if GPS is online, 0 otherwise 1454057376.6934643 gpsd_shm.status # Do we have a fix? 1 gpsd_shm.status == gpsdshm.STATUS_FIX True gpsd_shm.status == gpsdshm.STATUS_NO_FIX False gpsd_shm.skyview_time # Skyview timestamp gpsd_shm.satellites_visible # Number of satellites in view 6

GPS Fix

.. code-block:: python

gpsd_shm.fix.time # Time of update 1454057448.0 gpsd_shm.fix.mode # Mode of fix (0=not seen, 1=no fix, 2=2D, 3=3D) 3 gpsd_shm.fix.ept # Expected time uncertainty 0.005 gpsd_shm.fix.latitude # Latitude in degrees (valid if mode >= 2) -37.75859333333334 gpsd_shm.fix.epy # Latitude position uncertainty, meters 14.853882022256698 gpsd_shm.fix.longitude # Longitude in degrees (valid if mode >= 2) 144.99911 gpsd_shm.fix.epx # Longitude position uncertainty, meters 10.040781879264545 gpsd_shm.fix.alitude # Altitude in meters (valid if mode == 3) 68.2 gpsd_shm.fix.epv # Vertical position uncertainty, meters 19.55 gpsd_shm.fix.track # Course made good (relative to true north) 44.45 gpsd_shm.fix.epd # Track uncertainty, degrees nan gpsd_shm.fix.speed # Speed over ground, meters/sec 0.3446777748 gpsd_shm.fix.eps # Speed uncertainty, meters/sec 29.707764044513397 gpsd_shm.fix.climb # Vertical speed, meters/sec 0.0 gpsd_shm.fix.epc # Vertical speed uncertainty nan

Dilution of precisions (DOP)

.. code-block:: python

gpsd_shm.dop.xdop 0.6693854586176363 gpsd_shm.dop.ydop 0.9902588014837799 gpsd_shm.dop.pdop 1.17 gpsd_shm.dop.hdop 0.99 gpsd_shm.dop.vdop 0.82 gpsd_shm.dop.tdop 1.2548625723457216 gpsd_shm.dop.gdop 2.4342743978108503

Satellites

Information about satellites is contained in the satellites list. The list is always gpsdshm.MAXCHANNELS entries long, even if only a few satellites are visible.

.. code-block:: python

gpsd_shm.satellites[0].ss # Signal-to-noise ratio (dB) 16.0 gpsd_shm.satellites[0].used # Used in solution? False gpsd_shm.satellites[0].prn # PRNs of satellite 6 gpsd_shm.satellites[0].elevation # Elevation of satellite, degrees 56 gpsd_shm.satellites[0].azimuth # Azimuth, degrees 59

Devices

The devices list contains either information about all devices gpsd is currently monitoring (gpsd release 3.12 and later, gpsdshm.GPSD_API_MAJOR_VERSION == 6) or a single entry with information about the device that shipped the most recent update (gpsd release 3.11 and earlier, gpsdshm.GPSD_API_MAJOR_VERSION == 5).

.. code-block:: python

gpsd_shm.devices[0].path /dev/ttyAMA0 gpsd_shm.devices[0].flags && gpsdshm.SEEN_GPS 1 gpsd_shm.devices[0].flags && gpsdshm.SEEN_RTCM2 0 gpsd_shm.devices[0].flags && gpsdshm.SEEN_RTCM3 0 gpsd_shm.devices[0].flags && gpsdshm.SEEN_AIS 0 gpsd_shm.devices[0].driver

TODO

gpsd_shm.devices[0].subtype

TODO

gpsd_shm.devices[0].activated

TODO

gpsd_shm.devices[0].baudrate 4800 gpsd_shm.devices[0].stopbits 1 gpsd_shm.devices[0].parity # 'N', 'O', or 'E' N gpsd_shm.devices[0].cylce 1.0 gpsd_shm.devices[0].mincylce 1.0 gpsd_shm.devices[0].driver_mode 0

Compiling gpsd with shared memory support

.. code-block:: console

$ git clone git://git.sv.gnu.org/gpsd.git # git clone http://git.savannah.gnu.org/r/gpsd.git $ cd gpsd $ git tag $ git checkout release-3.16 $ scons prefix=/usr/local shm_export=yes $ sudo scons install

Then run start gpsd and check whether the shared segment has been created.

.. code-block:: console

$ sudo /usr/local/sbin/gpsd -n /dev/ttyAMA0 $ ipcs -m | grep 0x47505344 ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status
0x47505344 163844 root 666 31616 1