pyubx2

pyubx2 is an original python library for the UBX protocol.

UBX is a proprietary binary protocol implemented on u-blox © GPS/GNSS receiver modules.

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

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

Current Status

At time of writing the library implements a comprehensive set of inbound and outbound messages for generation 9 and earlier u-blox GPS/GNSS devices (NEO-9*, ZED-F9*), but is readily extensible.

Contributions and feedback welcome - see CONTRIBUTING.MD

Installation

pyubx2 is compatible with Python 3.6+ and has no third-party library dependencies.

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

python -m pip install --upgrade pyubx2

Reading (Streaming)

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). The function is thread-safe in so far as the incoming data stream object is thread-safe. UBXReader also implements an iterator.

The UBXReader constructor includes an optional validate flag which governs behaviour if the stream includes non-UBX data. If set to 'False' (the default), it will ignore such data and continue with the next valid UBX message. If set to 'True', it will raise a UBXStreamError.

Examples:

• Serial input - this example will ignore any non-UBX data.

>>> from serial import Serial
>>> from pyubx2 import UBXReader
>>> stream = Serial('COM6', 9600, timeout=3)
>>> ubr = UBXReader(stream)
>>> (raw_data, parsed_data) = ubr.read()

• File input (using iterator) - this example will produce a UBXStreamError if non-UBX data is encountered.

>>> import os
>>> from pyubx2 import UBXReader
>>> file = os.path.join(os.path.dirname(__file__), 'ubxdata.bin')
>>> stream = open(file, 'rb')
>>> ubr = UBXReader(stream, True)
>>> for (raw_data, parsed_data) in ubr: print(parsed_data)
...

Parsing

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

If the optional 'validate' parameter is set to True, parse will validate the supplied UBX message header, payload length and checksum. If any of these are not consistent with the message content, it will raise a UBXParseError. Otherwise, the function will automatically generate the appropriate payload length and checksum.

Example:

>>> from pyubx2 import UBXMessage
>>> msg = UBXMessage.parse(b'\xb5b\x05\x01\x02\x00\x06\x01\x0f\x38', True)
>>> print(msg)
<UBX(ACK-ACK, clsID=CFG, msgID=CFG-MSG)>
>>> msg = UBXMessage.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=403327000, velN=-1, velE=-21, velD=-4, speed=22, gSpeed=21, heading=128387, sAcc=67, cAcc=8056455)>

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

>>> msg
<UBX(NAV-POSLLH, iTOW=403667000, 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

Generating

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

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

1. ubxClass
2. ubxID
3. mode (0=GET, 1=SET, 2=POLL)
4. (optional) a series of keyword parameters representing the message payload

NB: Once instantiated, a UBXMessage object is immutable.

The 'ubxClass' and 'ubxID' parameters may be passed as lookup strings, integers or bytes.

The 'mode' parameter signifies whether the message payload refers to a:

• GET message (i.e. output from the receiver - NB these would normally be generated via the UBXMessage.parse() or UBXReader.read() methods but can also be created manually)
• SET message (i.e. input to the receiver)
• POLL message (i.e. input to the receiver in anticipation of a response back)

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.

e.g. 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 (assuming an output serial stream has been created as serialOut):

>>> 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\x036'
>>> 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 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().

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 ...)>

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)>

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, layers=b'\x01', position=b'\x00\x00', keys_01=1079115777, keys_02=1079181313)>

Wild card query to retrieve all CFG_MSGOUT (keyID 0x2091*) parameters (set bits 0..15 of the keyID to 0xffff):

>>> 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, layers=b'\x01', position=b'\x00\x00', keys_01=546439167)>
>>> position = 64 # retrieve next 64 results
>>> msg2of3 = UBXMessage.config_poll(layer, position, keys)
>>> print(msg2of3)
<UBX(CFG-VALGET, version=0, layers=b'\x01', position=b'@\x00', keys_01=546439167)>
>>> position = 128 # retrieve next 64 results
>>> msg3of3 = UBXMessage.config_poll(layer, position, keys)
>>> print(msg3of3)
<UBX(CFG-VALGET, version=0, layers=b'\x01', position=b'\x80\x00', keys_01=546439167)>

Examples

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

1. ubxstreamer.py illustrates how to implement a threaded serial reader for UBX messages using pyubx2.UBXReader.

2. ubxfile.py illustrates how to implement a binary file reader for UBX messages using the pyubx2.UBXReader iterator function.

3. ubxcfgval.py illustrates how to invoke the Generation 9 configuration interface to set the UART1/2 baud rates via CFG-VALSET, CF-VALDEL and CFG-VALGET messages.

4. ubxconfig.py illustrates how to invoke legacy (pre-Generation 9) configuration messages to set the UBX-NAV* message rates on the receiver's UART and USB ports. You can see the results using ubxstreamer.py.

5. ubxtracker.py illustrates a simple CLI tool to convert a binary UBX data dump (e.g. as produced by the PyGPSClient's data logging facility) to a *.gpx track file using pyubx2.UBXReader.

Extensibility

The UBX protocol is principally defined in the modules ubxtypes_*.py as a series of dictionaries. Additional message types can be readily added to the appropriate dictionary. 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 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. '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

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

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.

In exceptional cases the combination of class, id and mode is not sufficient to define the message's content. 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 ESF-MEAS, CFG-NMEA, RXM-PMP, RXM-PMREQ, RXM-RLM and most MGA message types.

Graphical Client

A python/tkinter graphical GPS client which supports both NMEA and UBX protocols (via pynmea2 and pyubx2 respectively) is under development at:

http://github.com/semuconsulting/PyGPSClient

Author Information

semuadmin@semuconsulting.com