What is gpsctl?
gpsctl is a utility program written for Raspberry Pi computers using a U-Blox GPS board. The author's rig is a Raspberry Pi 3 Model B with a Uputronix GPS board, which uses a U-Blox MAX-M8Q GPS module. Some of gpsctl's functions are generic for any GPS that streams NMEA data to a Linux serial port, and these should work on any Linux system. Most of gpsctl's functions, however, are quite specific to the U-Blox products, and use their proprietary UBX protocol (again, on a serial port).
Why does the world need gpsctl?
Well, probably the world doesn't actually need gpsctl - but if you happen to be attempting the same thing the author was, you might find it useful. Configuring and controlling a U-Blox GPS connected to a Linux host is a frustrating exercise. The author ran into this when implementing a stratum 1 NTP server using the aforementioned hardware. He needed to make some configuration changes to better support this. Those configuration changes required the use of the UBX protocol, and support for this on Linux is ... minimal. Hence gpsctl!
On the other hand, anyone trying to "talk" to a U-Blox GPS from a C program might find the code in gpsctl to be a useful building block. The code in gpsctl includes functions for sending and receiving UBX protocol messages, for interpreting them, modifying them, etc. This could easily be extended to serve other purposes; after all, not everyone lusts for a stratum 1 NTP server, and there might actually be other useful purposes for a GPS (though I can't think of one right now).
What, exactly, does gpsctl do?
Some gpsctl functions work for any GPS streaming NMEA data over a serial port:
- Echoes NMEA data to stdout, optionally filtered by NMEA message type.
- Infers the GPS' baud rate from the stream of NMEA data.
Other gpsctl functions are specific to U-Blox GPS hardware:
- Configures the baud rate that the U-Blox GPS uses for communication.
- Configures whether the U-Blox GPS transmits NMEA data.
- Infers the GPS' baud rate using the UBX protocol only.
- Configures the use of the European Galileo satellites (which is off by default in U-Blox 3.01 firmware) and enables NMEA version 4.1 output for Galileo
- Queries the U-Blox GPS for position, time, GPS version, GPS configuration, and GPS satellite information. The format of query results are selectable: either plain English or JSON.
- Tests the pulse-per-second output of the U-Blox GPS (fundamental for NTP).
- Configures the U-Blox GPS for maximum timing pulse accuracy (useful for building a stratum 1 NTP server based on the GPS' notion of time).
- Disables NMEA RMC, VTG, GSA, GSV, GLL, GGA messages and enables ZDA (for NTP driver 20 mode 8)
- Saves the U-Blox GPS configuration to on-module battery-backed memory.
- Resets the U-Blox GPS.
The only dependencies gpsctl has (other than the standard C library) is on the JSON library cJSON, iniparser, and the popular Raspberry Pi I/O library WiringPi. The source for iniparser and cJSON (which have MIT licenses) are incorporated in this project.
The WiringPi library must be present and linked.
Why is gpsctl's code so awful?
Mainly because this is the first C program the author has written in over 30 years, but also because the author has serious deficiencies in aptitude, intelligence, and knowledge (not to mention choices of hobbies).
How is gpsctl licensed?
gpsctl is licensed with the quite permissive MIT license:
Created: October 18, 2017 Author: Tom Dilatush email@example.com
Copyright 2017 Tom Dilatush
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so.
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE A AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
gpsctl -v verbosity (e.g. -vv) -q, --quiet quiet mode -p, --port port to use (default is /dev/serial0) -j, --json output in JSON format -a, --autobaud autodetect baud rate of the u-blox module (tries 230400, 115200, 57600, 38400, 19200, 9600) -b, --baud use specified baud rate -M, --minbaud minimum baud rate --test test PPS output from GPS -s, --sync sync mode ascii, nmea, or ubx (default is ubx) -B, --newbaud set GPS device and serial port to same new baud rate -n, --nmea turn NMEA output on or off (y/n) -Q, --query config / fix / satellites / version --galileo deprecated - same as --satellites --satellites configure satellites only use NMEA version 4.1 or higher if Galileo satellites are enabled --configure_for_timing set stationary mode, configure satellites (as above), disable NMEA RMC, VTG, GSA, GSV, GLL, GGA and enable ZDA --save_config save config to battery-backed RAM -e, --echo echo NMEA output --reset reset u-blox config to defaults
To autodetect the current baud rate, set the pi and u-blox module to 115200 baud, configure stationary mode, Galileo satellites, and NMEA ZDA output only, and to see what it's doing
gpsctl -a -B 115200 --configure_for_timing -vv
To autodetect the current baud rate and configure satellites only
gpsctl -a --satellites
To view the current u-blox config
gpsctl -a -Q config
New in version 0.7 and later
At long last, the file /etc/gpsctl.conf is parsed for configuration options.
The [gpsctl] section is used to determine which serial port gpsctl uses.
The other sections are honoured by --galileo and --configure_for_timing, and override the defaults if present.
Without the gpsctl.conf file the program's behaviour will be the same as with version 0.6.
An example which configures for Galileo satellites:
# # example gpsctl.conf which enables Galileo as in --galileo parameter # [gpsctl] port = /dev/ttyAMA0 # sync method: ASCII = 1, NMEA = 2, UBX = 3 sync method = 3 verbosity = 0 [NMEA] enabled = true version = 4.1 GGA = off GLL = off GSA = off GSV = off RMC = on VTG = off GRS = off GST = off ZDA = on [GPS] enabled = yes minimum channels=8 maximum channels=16 [SBAS] enabled = no minimum channels=1 maximum channels=3 [Galileo] enabled = yes minimum channels=4 maximum channels=8 [Beidou] enabled = no minimum channels=8 maximum channels=16 [IMES] enabled = no minimum channels=0 maximum channels=8 [QZSS] enabled = no minimum channels=0 maximum channels=3 [GLONASS] enabled = yes minimum channels=8 maximum channels=14 [Navigation Engine] # Dynamic model: Portable = 0, Stationary = 2, Pedestrian = 3, Automotive = 4, Sea = 5, Air1G = 6, Air2G = 7, Air4G = 8, Watch = 9 Dynamic model = 2 # Fix mode: 2D only = 1, 3D only = 2, auto 2D/3D = 3 Fix mode = 2 Fixed altitude (2D) = 0.00 meters Fixed altitude variance (2D) = 0.0000 meters^2 Minimum elevation = 20 degrees Position DoP mask = 10.0 Time DoP mask = 10.0 Position accuracy mask = 40 meters Time accuracy mask = 40 meters Static hold threshold = 0 cm/s Dynamic GNSS timeout = 60 seconds Threshold above C/No = 8 satellites C/No threshold = 20 dBHz Static hold max distance = 0 meters # UTC Standard: AutoUTC = 0, USNO_UTC = 3, GLONASS_UTC = 6, BeiDou_UTC = 7 UTC standard = 3 [Time Pulse] # the nanoseconds / microseconds after the numbers are just reminders, they don't mean anything to the config parser Antenna cable delay = 56 nanoseconds RF group delay = 20 ns Unlocked pulse period = 1000000 microseconds Unlocked pulse length = 0 Locked pulse period = 1000000 microseconds Locked pulse length = 500000 microseconds User configurable delay = 0
Why did you fork it, Phil?
It all started when I decided to build a Raspberry Pi Stratum 1 NTP server.
I found the original gpsctl when looking for something to configure my Raspberry Pi plus u-blox GPS to receive Galileo satellite output. And then I tinkered a bit, tweaking settings, recompiling, tweaking again, and so on.
Hence the idea to use a configuration file to drive it.