pyspartn 0.1.7

SPARTN protocol parser

pyspartn

Current Status | Installation | Reading | Parsing | Generating | Serializing | Examples | Graphical Client | Author & License

pyspartn is an original Python 3 parser for the SPARTN © GPS/GNSS protocol. SPARTN is an open-source GPS/GNSS differential correction or DGPS protocol published by u-blox.

SPARTN Protocol 2.01 (available in the public domain). © 2021 u-blox AG. All rights reserved.

The pyspartn homepage is located at https://github.com/semuconsulting/pyspartn.

This is an independent project and we have no affiliation whatsoever with u-blox.

FYI There are companion libraries which handle standard NMEA 0183 ©, UBX © (u-blox) and RTCM3 © GNSS/GPS messages:

• pyubx2 (FYI installing pyubx2 via pip also installs pynmeagps and pyrtcm)
• pynmeagps
• pyrtcm

Current Status

WORK IN PROGRESS - CURRENTLY IN PRE-ALPHA.

The SPARTNReader class is fully functional and is capable of parsing individual SPARTN transport-layer messages from a binary data stream containing solely SPARTN data, with their associated metadata (message type/subtype, payload length, encryption parameters, etc.).

The SPARTNMessage class implements a provisional decrypt and decode for OCB, HPAC and GAD message types but it has not yet been fully tested (appears to be working OK for HPAC messages).

There are some additional complexities for messages where timeTagtype = 0. See https://portal.u-blox.com/s/question/0D52p0000CimfsOCQQ/spartn-initialization-vector-iv-details for discussion.

Sphinx API Documentation in HTML format is available at https://www.semuconsulting.com/pyspartn.

Contributions welcome - please refer to CONTRIBUTING.MD.

Bug reports and Feature requests - please use the templates provided.

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Installation

pyspartn is compatible with Python >=3.8 and has no third-party library dependencies.

In the following, python & pip refer to the Python 3 executables. You may need to type python3 or pip3, depending on your particular environment.

The recommended way to install the latest version of pyspartn is with pip:

python -m pip install --upgrade pyspartn

If required, pyspartn can also be installed into a virtual environment, e.g.:

python3 -m pip install --user --upgrade virtualenv
python3 -m virtualenv env
source env/bin/activate (or env\Scripts\activate on Windows)
(env) python3 -m pip install --upgrade pyspartn
...
deactivate

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Reading (Streaming)

class pyspartn.spartnreader.SPARTNReader(stream, **kwargs)

You can create a SPARTNReader object by calling the constructor with an active stream object. The stream object can be any data stream which supports a read(n) -> bytes method (e.g. File or Serial, with or without a buffer wrapper). pyspartn implements an internal SocketStream class to allow sockets to be read in the same way as other streams (see example below).

Individual SPARTN messages can then be read using the SPARTNReader.read() function, which returns both the raw binary data (as bytes) and the parsed data (as a SPARTNMessage, via the parse() method). The function is thread-safe in so far as the incoming data stream object is thread-safe. SPARTNReader also implements an iterator.

Example - Serial input:

>>> from serial import Serial
>>> from pyspartn import SPARTNReader
>>> stream = Serial('/dev/tty.usbmodem14101', 9600, timeout=3)
>>>spr = SPARTNReader(stream)
>>> (raw_data, parsed_data) = spr.read()
>>> print(parsed_data)

Example - File input (using iterator).

>>> from pyspartn import SPARTNReader
>>> stream = open('spartndata.log', 'rb')
>>> spr = SPARTNReader(stream)
>>> for (raw_data, parsed_data) in spr: print(parsed_data)
...

Example - Socket input (using iterator):

>>> import socket
>>> from pyspartn import SPARTNReader
>>> stream = socket.socket(socket.AF_INET, socket.SOCK_STREAM):
>>> stream.connect(("localhost", 50007))
>>> spr = SPARTNReader(stream)
>>> for (raw_data, parsed_data) in spr: print(parsed_data)

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Parsing

You can parse individual SPARTN messages using the static SPARTNReader.parse(data) function, which takes a bytes array containing a binary SPARTN message and returns a SPARTNMessage object. The optional decode keyword argument signifies whether to decrypt and decode the full payload (default = False). If decode is set to True and the message is encrypted (eaf=1), the decryption key must be provided via the key keyword argument - see example below.

NB: Once instantiated, a SPARTNMMessage object is immutable.

Examples:

>>> from pyspartn import SPARTNReader
>>> msg = SPARTNReader.parse(b"s\x00\x12\xe2\x00|\x10[\x12H\xf5\t\xa0\xb4+\x99\x02\x15\xe2\x05\x85\xb7\x83\xc5\xfd\x0f\xfe\xdf\x18\xbe\x7fv \xc3`\x82\x98\x10\x07\xdc\xeb\x82\x7f\xcf\xf8\x9e\xa3ta\xad", decode=False)
>>> print(msg)
<SPARTN(SPARTN-1X-OCB-GPS, msgType=0, msgSubtype=0, nData=37, eaf=1, crcType=2, frameCrc=2, timeTagtype=0, gnssTimeTag=3970, solutionId=5, solutionProcId=11)>

The SPARTNMessage object exposes different public attributes depending on its message type or 'identity'. SPARTN data fields are denoted SFnnn - use the datadesc() helper method to obtain a more user-friendly text description of the data field.

>>> from pyspartn import SPARTNReader, datadesc
>>> msg = SPARTNReader.parse(b'\x73\x03\x35\xec\x08\xc7\xd4\x20\x70\x5b\x1f\xc ... \x1e\xbe\x18\x43\x2d\x57\xe7\xa7', decode=True, key="00112233445566778899aabbccddeeff")
>>> print(msg)
<SPARTN(SPARTN-1X-HPAC-GPS, msgType=1, nData=619, eaf=1, crcType=2, frameCrc=12, msgSubtype=0, timeTagtype=1, gnssTimeTag=419070990, solutionId=5, solutionProcId=11, encryptionId=1, encryptionSeq=63, authInd=1, embAuthLen=0, crc=5760935, SF005=508, SF068=1, SF069=0, SF030=9, SF031_01=0, SF039_01=0, SF040T_01=1, SF040I_01=1, SF041_01=1, SF042_01=2, SF043_01=127, SF044_01=1, SF048_01=213, SF049a_01=257, SF049b_01=253, SF054_01=1, SatBitmaskLen_01=0, SF011_01=70263185, SF055_01_01=6, SF056_01_01=1, SF060_01_01=8944, ... SF061b_09_08=8287)>
>>> msg.identity
'SPARTN-1X-HPAC-GPS'
>>> msg.gnssTimeTag
419070990
>>> msg.SF005
508
datadesc("SF005")
'Solution issue of update (SIOU)'

The payload attribute always contains the raw payload as bytes.

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Generating

class pyspartn.spartnmessage.SPARTNMessage(**kwargs)

You can create an SPARTNMessage object by calling the constructor with the following keyword arguments:

1. transport as bytes

Example:

>>> from pyspartn import SPARTNMessage
>>> msg = SPARTNMessage(transport=b"s\x00\x12\xe2\x00|\x10[\x12H\xf5\t\xa0\xb4+\x99\x02\x15\xe2\x05\x85\xb7\x83\xc5\xfd\x0f\xfe\xdf\x18\xbe\x7fv \xc3`\x82\x98\x10\x07\xdc\xeb\x82\x7f\xcf\xf8\x9e\xa3ta\xad")
>>> print(msg)
<SPARTN(SPARTN-1X-OCB-GPS, msgType=0, msgSubtype=0, nData=37, eaf=1, crcType=2, frameCrc=2, timeTagtype=0, gnssTimeTag=3970, solutionId=5, solutionProcId=11)>

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Serializing

The SPARTNMessage class implements a serialize() method to convert a SPARTNMMessage object to a bytes array suitable for writing to an output stream.

e.g. to create and send a 1005 message type:

>>> from serial import Serial
>>> serialOut = Serial('COM7', 38400, timeout=5)
>>> from pyspartn import SPARTNMessage
>>> msg = SPARTNMessage(transport=b"s\x00\x12\xe2\x00|\x10[\x12H\xf5\t\xa0\xb4+\x99\x02\x15\xe2\x05\x85\xb7\x83\xc5\xfd\x0f\xfe\xdf\x18\xbe\x7fv \xc3`\x82\x98\x10\x07\xdc\xeb\x82\x7f\xcf\xf8\x9e\xa3ta\xad")
>>> print(msg)
<SPARTN(SPARTN-1X-OCB-GPS, msgType=0, msgSubtype=0, nData=37, eaf=1, crcType=2, frameCrc=2, timeTagtype=0, gnssTimeTag=3970, solutionId=5, solutionProcId=11)>
>>> output = msg.serialize()
>>> output
b"s\x00\x12\xe2\x00|\x10[\x12H\xf5\t\xa0\xb4+\x99\x02\x15\xe2\x05\x85\xb7\x83\xc5\xfd\x0f\xfe\xdf\x18\xbe\x7fv \xc3`\x82\x98\x10\x07\xdc\xeb\x82\x7f\xcf\xf8\x9e\xa3ta\xad"
>>> serialOut.write(output)

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Examples

The following examples are available in the /examples folder:

1. sparnparser.py - illustrates how to parse SPARTN messages from a binary input file.
2. rxmpmp_extract_spartn.py - ilustrates how to parse SPARTN messages from the payload of a UBX RXM-PMP message output by an L-Band correction receiver (e.g. D9S).

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Graphical Client

A python/tkinter graphical GPS client which supports NMEA, UBX, RTCM3 and SPARTN protocols is available at:

https://github.com/semuconsulting/PyGPSClient

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Author & License Information

[e-mail]

pyspartn is maintained entirely by unpaid volunteers. It receives no funding from advertising or corporate sponsorship. If you find the library useful, a small donation would be greatly appreciated!