docs/hardware/gps.md

GPS

Location fun. Tracking, logging, etc

Inspiration / Further Reading

• https://github.com/wadda/gps3
• https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all
• https://learn.adafruit.com/assets/3715
• https://learn.adafruit.com/adafruit-ultimate-gps?view=all
• https://stackoverflow.com/questions/16989153/saving-gps-data-as-gpx
• http://www.catb.org/gpsd/gpspipe.html
• http://www.catb.org/gpsd/gpsd-time-service-howto.html#_feeding_chrony_from_gpsd
• http://thomasloughlin.com/gpspipe-gps-client/
• http://robotsforroboticists.com/chrony-gps-for-time-synchronization/
• https://forum.armbian.com/topic/4944-opi-zero-gps-ntpserver/
• http://darethehair.net/gps_time_server.html
• https://forum.armbian.com/topic/7033-solved-orangepi-one-1-pps-ntp-server/
• https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

Hardware

The author chose the Adafruit Ultimate GPS Breakout (link) for this guide. YMMV with other boards.

Pinout

• Connect vcc to a 3v source on the main expansion header
• Connect gnd to a gnd on the main expansion header
• Connect tx to rx pin of uart2 on the main expansion header
• Connect rx to tx pin of uart2 on the main expaions header
• Connect pps to the PA6 pin on the main expansion header

Setup

armbian-config # Enable hardware uart2 and pps-gpio
    # System
    # Hardware
    #   Enable uart2 option
    #   Enable pps-gpio option
    # Save/reboot
apt install gpsd gpsd-clients python-gps gpsbabel # necessary software
systemctl stop gpsd # stop gpsd to help with testin
gpsd -n -N -D 2 /dev/ttyS2 # run gpsd by hand
cgps -s # run a cli client to verify it works

Setup necessary gpsd defaults (daemon that provides location data to programs).

Edit /etc/default/gpsd

• Add /dev/ttyS2 to DEVICES
• Add -n to GPSD_OPTIONS

Chrony

Setup PPS for chrony

cat >> /boot/armbianEnv.txt <<EOF
# Orange Pi PC 2e PPS Pin
# param_pps_pin=PA6
# Pine64 PPS Pin
# param_pps_pin=PH9

EOF
systemctl reboot
demsg | grep -i pps # Verify pps is enabled and shows in the kernel

Add GPS as a time source to chrony

cat >> /etc/chrony/chrony.conf <<EOF
# set larger delay to allow the NMEA source to overlap with
# the other sources and avoid the falseticker status
refclock SHM 0 refid GPS precision 1e-1 offset 0.9999 delay 0.2
refclock PPS /dev/pps0 lock NMEA

EOF

systemctl restart chrony
cgps # look for ```Status:     3D FIX```
chronyc sources -v # Should show PPS and GPS time sources as having a recent reading
chronyc tracking # Further details

NTP For Network

To enable chrony on your lollipop as the ntp server for your local clients…

cat > /etc/Networkmanager/dnsmasq-shared.d/ntp.conf <<EOF
dhcp-options=option:ntp-server,172.30.0.1
EOF

GPX Tracks

NextCloud

GpxPod for NextCloud is a good viewer for GPX track recordings

Tracking

### GPX Files

You can convert raw ```nmea``` data from ```gpspipe``` using ```gpsbabel```

Examples

- ```gpsbabel -t -r -w -i nmea -f /tmp/xxx.nmea -o gpx -F xxx.gpx```
- ```gpsbabel -t -i nmea -f /tmp/xxx.nmea -x track,pack,split=5m,title="LOG # %Y%m%d-%H%M" -o gpx -F out.gpx```

## Automatic Logging

The Python program used here is in the ```scripts``` directory.

``` bash

mkdir -p /tank/gps_data
chown -R gpsd:root /tank/gps_data
# put gpslog.py at /usr/local/bin
cat > /etc/systemd/system/gps-logger.service <<EOF
[Unit]
Description=Simple gps logger
After=gpsd.service gpsd.socket

[Service]
User=gpsd
ExecStart=/usr/local/bin/gpslog.py
Restart=on-failure

[Install]
WantedBy=multi-user.target
EOF

systemctl daemon-reload
systemctl enable gps-logger
systemctl start gps-logger

Setup Auto GPX Track Creation/Upload

A handy trick for auto-converting your GPS log data as well as uploading it to NextCloud. The Python program used here is in the scripts directory.

cat > /etc/systemd/system/gpsconvert.service <<EOF
[Unit]
Description=Merge GPS logs and upload to NextCloud
After=gps-logger

[Service]
ExecStart=/usr/local/bin/gpsconvert.py
EOF

cat > /etc/systemd/system/gpsconvert.timer <<EOF
[Unit]
Description=Run GPS log merge

[Timer]
OnCalendar=hourly
Persistent=true

[Install]
WantedBy=timers.target
EOF

systemctl daemon-reload
systemctl enable gpsconvert.timer
systemctl start gpsconvert.timer

A-GPS

This sets up a form of A-GPS to speed locks when indoors or having a hard time getting a lock in general.

This setup is specific to the Adafruit Ultimate GPS modules. You’ll need to adapt this if using a different GPS receiver.

Setup mt3339 utils and get latest sattelite hints

apt install python-pip python-setuptools python-wheel python3-pip python3-setuptools python3-wheel geoip-bin
pip install -U pyserial && pip3 install -U pyserial
cd /opt
git clone https://github.com/f5eng/mt3339-utils.git
cd /opt/mt3339-utils
./eporetrieve 

Get your current ip address

Note: this MUST be done from your main internet connection, NOT VPN

curl http://ifconfig.co

Setup Maxmind GeoIP database

mkdir GeoLite2
cd GeoLite2
wget https://geolite.maxmind.com/download/geoip/database/GeoLite2-City.tar.gz
tar -xzf GeoLite2-City.tar.gz
cd ..

Get IP Address Location

pip3 install -U maxminddb
python3
import maxminddb
reader = maxminddb.open_database('./GeoLite2/GeoLite2-City_20190402/GeoLite2-City.mmdb')
rec = reader.get('anipaddress')
print('%s,%s,0' %(rec['location']['latitude'], rec['location']['longitude']))
exit()

Seed GPS Unit With Rough Location and System Time

systemctl stop gpsd gpsd.socket gpsconvert.timer gpsconvert.service gps-logger
./epoloader --speed 9600 --time - --location python_output ./MTK14.EPO /dev/ttyS2
systemctl restart gpsd gpsd.socket gpsconvert.timer gpsconvert.service gps-logger