pyubx2

pyubx2 is an original Python 3 library for the UBX © protocol. UBX is a proprietary binary protocol implemented on u-blox ™ GNSS/GPS receiver modules.

The pyubx2 homepage is located at https://github.com/semuconsulting/pyubx2.

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

FYI There is a companion library pynmeagps, which handles standard NMEA 0183 © GNSS/GPS messages.

Current Status

At time of writing the library implements a comprehensive set of inbound (SET/POLL) and outbound (GET) messages for u-blox GPS/GNSS devices from generation 6 through generation 10 (NEO-M6*, NEO-M7*, NEO-M8*, NEO-M9*, NEO-D9*, RCB-F9*, ZED-F9*, MAX-M10S, etc.), but is readily extensible. Refer to UBX_MSGIDS in ubxtypes_core.py for the complete dictionary of messages currently supported. UBX protocol information sourced from u-blox Interface Specifications © 2013-2021, u-blox AG.

Sphinx API Documentation in HTML format is available at https://www.semuconsulting.com/pyubx2.

Contributions welcome - please refer to CONTRIBUTING.MD.

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

Installation

pyubx2 is compatible with Python 3.6+ 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 pyubx2 is with pip:

python -m pip install --upgrade pyubx2

If required, pyubx2 can also be installed into a virtual environment, e.g.:

python -m pip install --user --upgrade virtualenv
python -m virtualenv env
source env/bin/activate (or env\Scripts\activate on Windows)
(env) python -m pip install --upgrade pyubx2
...
deactivate

UBX Message Categories - GET, SET, POLL

pyubx2 divides UBX messages into three categories, signified by the mode or msgmode parameter.

mode	description	defined in
GET (0x00)	output from the receiver (the default)	ubxtypes_get.py
SET (0x01)	command input to the receiver	ubxtypes_set.py
POLL (0x02)	query input to the receiver	ubxtypes_poll.py

If you're simply streaming and/or parsing the output of a UBX receiver, the mode is implicitly GET. If you want to create or parse an input (command or query) message, you must set the mode parameter to SET or POLL.

NB: Once instantiated, a UBXMessage object is immutable.

Reading (Streaming)

class pyubx2.ubxreader.UBXReader(stream, *args, **kwargs)

You can create a UBXReader 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).

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

The constructor accepts the following optional keyword arguments:

• ubxonly: True = raise error if stream contains non-UBX data, False = ignore non-UBX data (default)
• validate: VALCKSUM (0x01) = validate checksum (default), VALNONE (0x00) = ignore invalid checksum or length
• parsebitfield: 1 = parse bitfields ('X' type properties) as individual bit flags, where defined (default), 0 = leave bitfields as byte sequences
• decodenavdata: 1 = decode nav data contained in RXM-SFRBX message, 0 = do not decode data (default)
• msgmode: 0 = GET (default), 1 = SET, 2 = POLL

Example - Serial input. This example will ignore any non-UBX data:

>>> from serial import Serial
>>> from pyubx2 import UBXReader
>>> stream = Serial('/dev/tty.usbmodem14101', 9600, timeout=3)
>>> ubr = UBXReader(stream)
>>> (raw_data, parsed_data) = ubr.read()
>>> print(parsed_data)

Example - File input (using iterator). This example will produce a UBXStreamError if non-UBX data is encountered:

>>> from pyubx2 import UBXReader
>>> stream = open('ubxdata.bin', 'rb')
>>> ubr = UBXReader(stream, ubxonly=True)
>>> for (raw_data, parsed_data) in ubr: print(parsed_data)
...

Parsing

You can parse individual UBX messages using the static UBXReader.parse(data) function, which takes a bytes array containing a binary UBX message and returns a UBXMessage object.

The parse() method accepts the following optional keyword arguments:

• validate: VALCKSUM (0x01) = validate checksum (default), VALNONE (0x00) = ignore invalid checksum or length
• parsebitfield: 1 = parse bitfields as individual bit flags, where defined (default), 0 = leave bitfields as byte sequences
• decodenavdata: 1 = decode nav data contained in RXM-SFRBX message, 0 = do not decode data (default)
• msgmode: 0 = GET (default), 1 = SET, 2 = POLL

Properties within repeating groups are parsed with a two-digit suffix (svid_01, svid_02, etc.).

Example - output (GET) message:

>>> from pyubx2 import UBXReader
>>> msg = UBXReader.parse(b'\xb5b\x05\x01\x02\x00\x06\x01\x0f\x38')
>>> print(msg)
<UBX(ACK-ACK, clsID=CFG, msgID=CFG-MSG)>
>>> msg = UBXReader.parse(b'\xb5b\x01\x12$\x000D\n\x18\xfd\xff\xff\xff\xf1\xff\xff\xff\xfc\xff\xff\xff\x10\x00\x00\x00\x0f\x00\x00\x00\x83\xf5\x01\x00A\x00\x00\x00\xf0\xdfz\x00\xd0\xa6')
>>> print(msg)
<UBX(NAV-VELNED, iTOW=16:01:50, velN=-3, velE=-15, velD=-4, speed=16, gSpeed=15, heading=128387, sAcc=65, cAcc=8052720)>

Example - input (SET) message:

>>> from pyubx2 import UBXReader, SET
>>> msg = UBXReader.parse(b"\xb5b\x13\x40\x14\x00\x01\x00\x01\x02\x01\x02\x03\x04\x01\x02\x03\x04\x01\x02\x03\x04\x01\x02\x03\x04\x93\xc8", msgmode=SET)
>>> print(msg)
<UBX(MGA-INI-POS_LLH, type=1, version=0, reserved1=513, lat=67305985, lon=67305985, alt=67305985, posAcc=67305985)>

The UBXMessage object exposes different public properties depending on its message type or 'identity', e.g. the NAV-POSLLH message has the following properties:

>>> print(msg)
<UBX(NAV-POSLLH, iTOW=16:01:54, lon=-21601284, lat=526206345, height=86327, hMSL=37844, hAcc=38885, vAcc=16557)>
>>> msg.identity
'NAV-POSLLH'
>>> msg.lat/10**7, msg.lon/10**7
(52.6206345, -2.1601284)
>>> msg.hMSL/10**3
37.844

The payload property always contains the raw payload as bytes.

Generating

(see below for special methods relating to the UBX configuration interface)

class pyubx2.ubxmessage.UBXMessage(ubxClass, ubxID, mode: int, **kwargs)

You can create a UBXMessage object by calling the constructor with the following parameters:

1. message class (must be a valid class from pyubx2.UBX_CLASSES)
2. message id (must be a valid id from pyubx2.UBX_MSGIDS)
3. mode (0=GET, 1=SET, 2=POLL)
4. (optional) a series of keyword parameters representing the message payload
5. (optional) parsebitfield keyword - 1 = define bitfields as individual bits (default), 0 = define bitfields as byte sequences

The 'message class' and 'message id' parameters may be passed as lookup strings, integers or bytes.

The message payload can be defined via keyword parameters in one of three ways:

1. A single keyword parameter of payload containing the full payload as a sequence of bytes (any other keyword parameters will be ignored). NB the payload keyword must be used for message types which have a 'variable by size' repeating group.
2. One or more keyword parameters corresponding to individual message attributes. Any attributes not explicitly provided as keyword parameters will be set to a nominal value according to their type.
3. If no keyword parameters are passed, the payload is assumed to be null.

Example - to generate a CFG-MSG which polls the 'VTG' NMEA message rate on the current port, any of the following constructor formats will work:

>>> from pyubx2 import UBXMessage, POLL
>>> msg1 = UBXMessage(b'\x06', b'\x01', POLL, payload=b'\xf0\x05')
>>> print(msg1)
<UBX(CFG-MSG, msgClass=NMEA-Standard, msgID=VTG)>

>>> from pyubx2 import UBXMessage, POLL
>>> msg2 = UBXMessage(6, 1, POLL, msgClass=240, msgID=5)
>>> print(msg2)
<UBX(CFG-MSG, msgClass=NMEA-Standard, msgID=VTG)>

>>> from pyubx2 import UBXMessage, POLL
>>> msg3 = UBXMessage('CFG','CFG-MSG', POLL, msgClass=240, msgID=5)
>>> print(msg3)
<UBX(CFG-MSG, msgClass=NMEA-Standard, msgID=VTG)>

Serializing

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

e.g. to create and send a CFG-MSG message which sets the NMEA GLL message rate to '1' on the receiver's UART1 and USB ports:

>>> from serial import Serial
>>> serialOut = Serial('COM7', 38400, timeout=5)
>>> from pyubx2 import UBXMessage, SET
>>> msg = UBXMessage('CFG','CFG-MSG', SET, msgClass=240, msgID=1, rateUART1=1, rateUSB=1)
>>> print(msg)
<UBX(CFG-MSG, msgClass=NMEA-Standard, msgID=GLL, rateDDC=0, rateUART1=1, rateUART2=0, rateUSB=1, rateSPI=0, reserved=0)>
>>> output = msg.serialize()
>>> output
b'\xb5b\x06\x01\x08\x00\xf0\x01\x00\x01\x00\x01\x00\x00\x022'
>>> serialOut.write(output)

Configuration Interface

CFG-VALSET, CFG-VALDEL and CFG-VALGET message types

Generation 9 of the UBX protocol introduced the concept of a device configuration interface with configurable parameters being set or unset (del) in the designated memory layer(s) via the CFG-VALSET and CFG-VALDEL message types, or queried via the CFG-VALGET message type. Legacy CFG message types continue to be supported but are now deprecated.

Optionally, batches of CFG-VALSET and CFG-VALDEL messages can be applied transactionally, with the combined configuration only being committed at the end of the transaction.

Individual configuration parameters are designated by keys, which may be in string (keyname) or hexadecimal integer (keyID) format. Keynames and their corresponding hexadecimal keyIDs and data types are defined in ubxtypes_configdb.py as UBX_CONFIG_DATABASE. Two static helper methods are available to convert keyname to keyID and vice versa - UBXMessage.cfgname2key() and UBXMessage.cfgkey2name().

Dedicated static methods are provided to create these message types - UBXMessage.config_set(), UBXMessage.config_del() and UBXMessage.config_poll(). The following examples assume an output serial stream has been created as serialOut.

UBXMessage.config_set() (CFG-VALSET)

Sets up to 64 parameters in the designated memory layer(s).

Parameters:

1. layers - 1 = Volatile RAM, 2 = Battery-Backed RAM (BBR), 4 = External Flash
2. transaction - 0 = None, 1 = Start, 2 = Ongoing, 3 = Commit
3. cfgData - an array of up to 64 (key, value) tuples. Keys can be in either keyID (int) or keyname (str) format

>>> from pyubx2 import UBXMessage
>>> layers = 1
>>> transaction = 0
>>> cfgData = [("CFG_UART1_BAUDRATE", 9600), (0x40530001, 115200)]
>>> msg = UBXMessage.config_set(layers, transaction, cfgData)
>>> print(msg)
<UBX(CFG-VALSET, version=0, layers=b'\x01', transaction=0, reserved0=0, cfgData_01=1, cfgData_02=0 ...)>
>>> serialOut.write(msg.serialize())

UBXMessage.config_del() (CFG-VALDEL)

Unsets (deletes) up to 64 parameter settings in the designated non-volatile memory layer(s).

Parameters:

1. layers - 2 = Battery-Backed RAM (BBR), 4 = External Flash
2. transaction - 0 = None, 1 = Start, 2 = Ongoing, 3 = Commit
3. keys - an array of up to 64 keys in either keyID (int) or keyname (str) format

>>> from pyubx2 import UBXMessage
>>> layers = 4
>>> transaction = 0
>>> keys = ["CFG_UART1_BAUDRATE", 0x40530001]
>>> msg = UBXMessage.config_del(layers, transaction, keys)
>>> print(msg)
<UBX(CFG-VALDEL, version=0, layers=b'\x04', transaction=b'\x00', reserved0=0, keys_01=1079115777, keys_02=1079181313)>
>>> serialOut.write(msg.serialize())

UBXMessage.config_poll() (CFG-VALGET)

Polls up to 64 parameters from the designated memory layer.

Parameters:

1. layer - 0 = Volatile RAM, 1 = Battery-Backed RAM (BBR), 2 = External Flash, 7 = Default (readonly)
2. position - unsigned integer representing number of items to be skipped before returning result (used when number of matches for an individual query exceeds 64)
3. keys - an array of up to 64 keys in either keyID (int) or keyname (str) format. keyIDs can use wildcards - see example below and UBX device interface specification for details.

>>> from pyubx2 import UBXMessage
>>> layer = 1
>>> position = 0
>>> keys = ["CFG_UART1_BAUDRATE", 0x40530001]
>>> msg = UBXMessage.config_poll(layer, position, keys)
>>> print(msg)
<UBX(CFG-VALGET, version=0, layer=1, position=0, keys_01=1079115777, keys_02=1079181313)>
>>> serialOut.write(msg.serialize())

Wild card queries can be performed by setting bits 0..15 of the keyID to 0xffff e.g. to retrieve all CFG_MSGOUT parameters (keyID 0x2091*) :

>>> from pyubx2 import UBXMessage
>>> layer = 1
>>> position = 0 # retrieve first 64 results
>>> keys = [0x2091ffff]
>>> msg1of3 = UBXMessage.config_poll(layer, position, keys)
>>> print(msg1of3)
<UBX(CFG-VALGET, version=0, layer=1, position=0, keys_01=546439167)>
>>> serialOut.write(msg1of3.serialize())
>>> position = 64 # retrieve next 64 results
>>> msg2of3 = UBXMessage.config_poll(layer, position, keys)
>>> print(msg2of3)
<UBX(CFG-VALGET, version=0, layer=1, position=64, keys_01=546439167)>
>>> serialOut.write(msg2of3.serialize())
>>> position = 128 # retrieve next 64 results
>>> msg3of3 = UBXMessage.config_poll(layer, position, keys)
>>> print(msg3of3)
<UBX(CFG-VALGET, version=0, layer=1, position=128, keys_01=546439167)>
>>> serialOut.write(msg3of3.serialize())

Examples

The following examples can be found in the \examples folder:

1. ubxoptions.py illustrates the various options available for parsing and constructing UBX messages.
2. ubxstreamer.py illustrates how to implement a threaded serial reader for UBX messages using pyubx2.UBXReader.
3. ubxfile.py illustrates how to implement a binary file reader for UBX messages using the pyubx2.UBXReader iterator function.
4. ubxcfgval.py illustrates how to invoke the Generation 9 configuration interface via CFG-VALSET, CF-VALDEL and CFG-VALGET messages.
5. ubxconfig.py illustrates how to invoke legacy (pre-Generation 9) configuration messages (CFG-MSG).
6. gpxtracker.py illustrates a simple CLI tool to convert a binary UBX data dump to a *.gpx track file.
7. benchmark.py illustrates a simple performance benchmarking tool for the pyubx2 parser.

Extensibility

The UBX protocol is principally defined in the modules ubxtypes_*.py as a series of dictionaries. Message payload definitions must conform to the following rules:

1. attribute names must be unique within each message class
2. attribute types must be one of the valid types (I1, U2, X4, etc.)
3. repeating or bitfield groups must be defined as a tuple ('numr', {dict}), where:
   'numr' is either:
     a. an integer representing a fixed number of repeats e.g. 32
     b. a string representing the name of a preceding attribute containing the number of repeats e.g. 'numCh'
     c. an 'X' attribute type ('X1', 'X2', 'X4', etc) representing a group of individual bit flags
     d. 'None' for a 'variable by size' repeating group. Only one such group is permitted per payload and it must be at the end.
   {dict} is the nested dictionary of repeating items or bitfield group

Repeating attribute names are parsed with a two-digit suffix (svid_01, svid_02, etc.). Nested repeating groups are supported. See CFG-VALGET, MON-SPAN, NAV-PVT, NAV-SAT and RXM-RLM by way of examples.

In most cases, a UBX message's content (payload) is uniquely defined by its class, id and mode; accommodating the message simply requires the addition of an appropriate dictionary entry to the relevant ubxtypes_*.py module(s).

However, there are a handful of message types which have multiple possible payload definitions for the same class, id and mode, with no consistency as to how to differentiate between them. Under these circumstances, it may be necessary to modify the code in ubxmessage.py to examine elements of the payload itself in order to determine the appropriate dictionary definition. This currently applies to CFG-NMEA, RXM-PMP, RXM-PMREQ, RXM-RLM and most MGA message types.

Command Line Utility

If pyubx2 is installed using pip, a simple command line utility ubxdump is automatically installed into the Python 3 scripts (bin) directory. This utility streams the parsed UBX output of a u-blox GNSS device to the terminal.

Assuming the Python 3 scripts (bin) directory is in your PATH, the utility may be invoked thus (all args are optional):

ubxdump port=/dev/ttyACM1 baud=9600 timeout=5 ubxonly=0 validate=1 output=0 parsebitfield=1 filter=*

Optional Args:

• port: serial port e.g. COM3 or /dev/ttyACM1 (default /dev/ttyACM1)
• baudrate: e.g. 9600 (default 9600)
• ubxonly: 0 = ignore non-UBX data (default), 1 = terminate on any non-UBX data (e.g. NMEA).
• validate: 1 = validate checksum (default), 0 = do not validate checksum
• output: 0 = parsed (default), 1 = binary, 2 = hexadecimal
• parsebitfield: 1 = parse bitfields as individual bits (default), 0 = leave bitfields as byte sequences
• decodenavdata: 1 = decode nav data contained in RXM-SFRBX message, 0 = do not decode data (default)
• filter: comma-separated list of specific UBX message identities to display e.g. filter=NAV-PVT,NAV-CLOCK (defaults to "*" - all UBX messages).

For help, type:

ubxdump -h

Graphical Client

A python/tkinter graphical GPS client which supports both NMEA and UBX protocols (via pynmeagps and pyubx2 respectively) is available at:

https://github.com/semuconsulting/PyGPSClient

Author Information

semuadmin@semuconsulting.com