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UBX protocol parser and generator

Project description


Current Status | Installation | Message Categories | Reading | Parsing | Generating | Serializing | Configuration Interface | Utilities | Examples | Extensibility | Troubleshooting | Command Line Utility | Graphical Client | Author & License

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

pyubx2 is also capable of parsing NMEA 0183 © and RTCM3 © GNSS/GPS messages via the following inbuilt companion libraries:

The pyubx2 homepage is located at

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

Current Status

Status Release Build Codecov Release Date Last Commit Contributors Open Issues

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 for the complete dictionary of messages currently supported. UBX protocol information sourced from public domain u-blox Interface Specifications © 2013-2021, u-blox AG.

Sphinx API Documentation in HTML format is available at

Contributions welcome - please refer to CONTRIBUTING.MD. Feel free to discuss any proposed changes beforehand in the Discussion Channel.

Bug reports and Feature requests - please use the templates provided. For general queries and advice, post a message to one of the pyubx2 Discussions channels.


pyubx2 is compatible with Python >=3.8. In the following, python3 & pip refer to the Python 3 executables. You may need to type python or pip3, depending on your particular environment.

Python version PyPI version PyPI downloads

The recommended way to install the latest version of pyubx2 is with pip:

python3 -m pip install --upgrade pyubx2

If required, pyubx2 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 pyubx2

For Conda users, pyubx2 is also available from conda forge:

Anaconda-Server Badge Anaconda-Server Badge

conda install -c conda-forge pyubx2

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)
SET (0x01) command input to the receiver
POLL (0x02) query input to the receiver

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. If the parser mode is set to 0x03 (SETPOLL), pyubx2 will automatically determine the applicable input mode (SET or POLL) based on the message payload.

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). pyubx2 implements an internal SocketStream class to allow sockets to be read in the same way as other streams (see example below).

Individual input UBX, NMEA or RTCM3 messages can then be read using the function, which returns both the raw binary data (as bytes) and the parsed data (as a UBXMessage, NMEAMessage or RTCMMessage 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:

  • protfilter: 1 = NMEA, 2 = UBX, 4 = RTCM3 (can be OR'd. default is 3 - NMEA & UBX)
  • quitonerror: 0 = ignore errors, 1 = log errors and continue (default), 2 = (re)raise errors and terminate
  • 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
  • msgmode: 0 = GET (default), 1 = SET, 2 = POLL, 3 = SETPOLL (automatically determine SET or POLL input mode)

Example - Serial input. This example will output both UBX and NMEA messages:

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

Example - File input (using iterator). This will only output UBX data:

>>> from pyubx2 import UBXReader
>>> stream = open('ubxdata.bin', 'rb')
>>> ubr = UBXReader(stream, protfilter=2)
>>> for (raw_data, parsed_data) in ubr: print(parsed_data)

Example - Socket input (using iterator). This will output UBX, NMEA and RTCM3 data:

>>> import socket
>>> from pyubx2 import UBXReader
>>> stream = socket.socket(socket.AF_INET, socket.SOCK_STREAM):
>>> stream.connect(("localhost", 50007))
>>> ubr = UBXReader(stream, protfilter=7)
>>> for (raw_data, parsed_data) in ubr: print(parsed_data)


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.

NB: Once instantiated, a UBXMessage object is immutable.

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
  • msgmode: 0 = GET (default), 1 = SET, 2 = POLL, 3 = SETPOLL (automatically determine SET or POLL input mode)

Example - output (GET) message:

>>> from pyubx2 import UBXReader
>>> msg = UBXReader.parse(b'\xb5b\x05\x01\x02\x00\x06\x01\x0f\x38')
>>> print(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=16:01:48, velN=-3, velE=-15, velD=-4, speed=16, gSpeed=15, heading=1.28387, sAcc=65, cAcc=80.5272)>

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, reserved0=513, lat=6.7305985, lon=6.7305985, alt=67305985, posAcc=67305985)>

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

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

The payload attribute always contains the raw payload as bytes. Attributes within repeating groups are parsed with a two-digit suffix (svid_01, svid_02, etc.).

Tip: To iterate through a repeating group of attributes (e.g., svid), the following construct can be used:

svids = [] # list of svid values from repeating group
size = msg.numSV # size of repeating group
for i in range(size):
    svid = getattr(msg, f"svid_{i+1:02}")

If the input message class / id is unrecognised (i.e. not publicly documented by u-blox), pyubx2 will parse the message to a nominal payload definition and append the term 'NOMINAL' to the message identity.


(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 arguments in one of three ways:

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

Example - to generate a CFG-MSG command (msgClass 0x06, msgID 0x01) which sets the NAV-STATUS (msgClass 0x01, msgID 0x03) outbound message rate to 1 on the UART1 port, any of the following constructor formats will work:

A. Pass entire payload as bytes:

>>> from pyubx2 import UBXMessage, SET
>>> msg1 = UBXMessage(b'\x06', b'\x01', SET, payload=b'\x01\x03\x00\x01\x00\x00\x00\x00')
>>> print(msg1)
<UBX(CFG-MSG, msgClass=NAV, msgID=NAV-STATUS, rateDDC=0, rateUART1=1, rateUART2=0, rateUSB=0, rateSPI=0, reserved=0)>

B. Pass individual attributes as keyword arguments:

>>> from pyubx2 import UBXMessage, SET
>>> msg2 = UBXMessage(0x06, 0x01, SET, msgClass=0x01, msgID=0x03, rateDDC=0, rateUART1=1, rateUART2=0, rateUSB=0, rateSPI=0)
>>> print(msg2)
<UBX(CFG-MSG, msgClass=NAV, msgID=NAV-STATUS, rateDDC=0, rateUART1=1, rateUART2=0, rateUSB=0, rateSPI=0, reserved=0)>

C. Pass selected attribute as keyword argument; the rest will be set to nominal values (in this case 0):

>>> from pyubx2 import UBXMessage, SET
>>> msg3 = UBXMessage('CFG','CFG-MSG', SET, msgClass=0x01, msgID=0x03, rateUART1=1)
>>> print(msg3)
<UBX(CFG-MSG, msgClass=NAV, msgID=NAV-STATUS, rateDDC=0, rateUART1=1, rateUART2=0, rateUSB=0, rateSPI=0, reserved=0)>


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 command which sets the NMEA GLL (msgClass 0xf0, msgID 0x01) 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=0xf0, msgID=0x01, 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
>>> serialOut.write(output)

Configuration Interface


Generation 9 of the UBX protocol (23.01 or greater, e.g. NEO-M9N, ZED-F9P) 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 configuration message types continue to be supported but are now deprecated on Generation 9+ devices.

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 as UBX_CONFIG_DATABASE. Two helper methods are available to convert keyname to keyID and vice versa - cfgname2key() and 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).


  1. layers - 1 = Volatile RAM, 2 = Battery-Backed RAM (BBR), 4 = External Flash (may be OR'd)
  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, ram=1, bbr=0, flash=0, action=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).


  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, bbr=0, flash=1, action=0, 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.


  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())

Utility Methods

pyubx2 provides the following utility methods (via the pynmeagps library):

  • latlon2dms - converts decimal lat/lon to degrees, minutes, decimal seconds format e.g. "53°20′45.6″N", "2°32′46.68″W"
  • latlon2dmm - converts decimal lat/lon to degrees, decimal minutes format e.g. "53°20.76′N", "2°32.778′W"
  • ecef2llh - converts ECEF (X, Y, Z) coordinates to geodetic (lat, lon, ellipsoidal height) coordinates
  • llh2ecef - converts geodetic (lat, lon, ellipsoidal height) coordinates to ECEF (X, Y, Z) coordinates
  • haversine - finds spherical distance in km between two sets of (lat, lon) coordinates
  • bearing - finds bearing in degrees between two sets of (lat, lon) coordinates
  • cel2cart - converts celestial coordinates (elevation, azimuth) to cartesian coordinations (X,Y)

See Sphinx documentation for details.


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

  1. illustrates the various options available for parsing and constructing UBX messages.
  2. illustrates how to read, write and display UBX messages 'concurrently' using threads and queues. This represents a useful generic pattern for many end user applications.
  3. illustrates how to use legacy configuration messages (CFG-MSG) to set navigation message rates.
  4. illustrates how to invoke the Generation 9 configuration database interface via CFG-VALSET, CF-VALDEL and CFG-VALGET messages.
  5. illustrates how to send a factory reset (CFG-CFG) command.
  6. illustrates how to implement a binary file reader for UBX messages using UBXReader iterator functionality.
  7. illustrates how to implement a TCP Socket reader for UBX messages using UBXReader iterator functionality. Can be used in conjunction with the socket server test harness.
  8. illustrates a simple tool to convert a binary UBX data dump to a *.gpx track file.
  9. in the \examples\webserver folder illustrates a simple HTTP web server wrapper around pyubx2.UBXreader; it presents data from selected UBX messages as a web page http://localhost:8080 or a RESTful API http://localhost:8080/gps.
  10. illustrates how to use pyubx2 and matplotlib to plot a spectrum analysis graph from a UBX MON-SPAN message.
  11. illustrates how to use various pyubx2 utility methods.
  12. provides a simple performance benchmarking tool for the pyubx2 parser.


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. if the attribute is scaled, attribute type is list of [attribute type as string (I1, U2, etc.), scaling factor as float] e.g. {"lat": [I4, 1e-7]}
4. 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. These exceptional message types require dedicated routines in which examine elements of the payload itself in order to determine the appropriate dictionary definition. This currently applies to the following message types: CFG-NMEA, NAV-RELPOSNED, RXM-PMP, RXM-PMREQ, RXM-RLM, TIM-VCOCAL.


1. Unknown Protocol errors.

These are usually due to corruption of the serial data stream, either because the serial port configuration is incorrect (baud rate, parity, etc.) or because another process is attempting to use the same data stream.

  • Check that your UBX receiver UART1 or UART2 ports are configured for the desired baud rate - remember the factory default is 38400 (not 9600).
  • Check that no other process is attempting to use the same serial port, including daemon processes like gpsd.

2. Serial Permission errors.

These are usually caused by inadequate user privileges or contention with another process.

  • On Linux platforms, check that the user is a member of the tty and/or dialout groups.
  • Check that no other process is attempting to use the same serial port, including daemon processes like gpsd.

3. UnicodeDecode errors.

  • If reading UBX data from a log file, check that the procedure is using the rb (read binary) setting e.g. stream = open('ubxdatalog.log', 'rb').

4. Spurious CFG-VALGET, DBG, TRK, TUN and SEC data in *.ubx files recorded in u-center.

By default, u-center 21.09 records a series of configuration messages (CFG-VALGET) containing undocumented configuration database keys. In addition, clicking the 'debug' option results in a large number of undocumented DBG, TRK, TUN and SEC message classes. As of version v1.2.15, pyubx2 is capable of parsing these undocumented message classes (to a nominal payload definition), but they are really only of relevance to u-blox technical support. If you are not intending to send the recordings to u-blox;

  • When recording GNSS output data in u-center, select 'No' when prompted to 'Add Receiver Configuration' to the recording, and avoid the 'debug' option.

Command Line Utility

A command line utility gnssdump is available via the pygnssutils package. This is capable of reading and parsing NMEA, UBX and RTCM3 data from a variety of input sources (e.g. serial, socket and file) and outputting to a variety of media in a variety of formats. See for further details.

To install pygnssutils:

python3 -m pip install --upgrade pygnssutils

For help with the gnssdump utility, type:

gnssdump -h

Graphical Client

A python/tkinter graphical GPS client which supports NMEA, UBX and RTCM3 protocols (via pynmeagps, pyubx2 and pyrtcm respectively) is available at:

Author & License Information


pyubx2 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!


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