Fix Quality 3d returns undocumented values

[jar349]

The documented values for fix_quality_3d are as follows in the snippet below:

Adafruit_CircuitPython_GPS/adafruit_gps.py

Lines 272 to 279 in 41f1596

	self.fix_quality_3d = 0
	"""
	The type of fix for a reading
	| 1 - no fix
	| 2 - 2D fix
	| 3 - 3D fix
	"""

However, the value I am getting for that attribute is 0. If this is an expected value under certain conditions, would you mind updating the documentation to explain? If it is never expected for the value to be 0, could you please explain what I may be doing wrong on my end to receive that value? All other values I am getting look good/correct.

I suspect that the culprit is this block of code:

Adafruit_CircuitPython_GPS/adafruit_gps.py

Lines 634 to 642 in 3e13731

	if data is None or len(data) not in (17, 18):
	return False # Unexpected number of params.
	if len(data) == 17:
	data = _parse_data(_GSA, data)
	else:
	data = _parse_data(_GSA_4_11, data)
	if data is None:
	self.fix_quality_3d = 0
	return False # Params didn't parse

If there's code beyond initializing it to 0 that sets it to 0 - as this block does - then 0 probably does have a semantic meaning that can be documented.

[snkYmkrct]

@jar349
The GPS module only shows the data (NMEA sentences) specified in its initialization commands.
This is documented in the usage example code:

Adafruit_CircuitPython_GPS/examples/gps_simpletest.py

Lines 31 to 44 in 3e13731

	# Initialize the GPS module by changing what data it sends and at what rate.
	# These are NMEA extensions for PMTK_314_SET_NMEA_OUTPUT and
	# PMTK_220_SET_NMEA_UPDATERATE but you can send anything from here to adjust
	# the GPS module behavior:
	# https://cdn-shop.adafruit.com/datasheets/PMTK_A11.pdf
	# Turn on the basic GGA and RMC info (what you typically want)
	gps.send_command(b"PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0")
	# Turn on just minimum info (RMC only, location):
	# gps.send_command(b'PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')
	# Turn off everything:
	# gps.send_command(b'PMTK314,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')
	# Turn on everything (not all of it is parsed!)
	# gps.send_command(b'PMTK314,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0')

as well as in the referenced command packet document -- see page 12 -- and various learn guides on the Adafruit page, like this one.

Since the fix_quality parameter is part of the GSA NMEA sentence, GSA data needs to be enabled in the initialization command, like so: gps.send_command(b"PMTK314,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0"). Otherwise, the behavior you're observing is correct, self.fix_quality_3d is 0 because there is no valid data to be parsed, and this is the default value.
The "culprit" you're referring to is also correct behavior, since it only occurs when that particular GSA data packet is corrupted, and cannot be parsed.

Usually it's better, and faster, to ask for library usage help on the Adafruit forums, or in the Discord server.