BeagleBone Black Time Server

Stratum 1 GNSS NTP Server running on a BeagleBone Black

Equipment

These are the parts I have used.

• BeagleBone Black
• SparkFun ublox NEO-M9N
  • I went a little overkill on this one, but this module supports GPS, GLONASS, BeiDou, and Galileo
  • This Adafruit module is a good alternative
• Adafruit DS3231 RTC
• Some cheap Active GPS Antenna
• uFL to SMA Adapter Pigtail (Example)
• Pin Headers for the GNSS module (Soldering required)
• Some Male-to-Female DuPont Cables

Wiring

BBB	GNSS Module
5V	5V
GND	GND
P9_11 (UART4_TX)	RX
P9_13 (UART4_RX)	TX
P9_12 (GPIO 60)	PPS

Setup

1. Install Debian Minimal on the BeagleBone Black

2. Install packages:

sudo apt update
sudo apt install git build-essential pps-tools gpsd chrony nginx php-fpm php-gd

3. Compile PPS device tree

• Clone bb.org-overlays repo:

  git clone https://github.com/beagleboard/bb.org-overlays

• Copy DD-PPS-00A0.dts into cloned bb.org-overlays/src/arm/.

• Compile .dtbo and place in /lib/firmware:

  make src/arm/DD-PPS.dtbo
  sudo cp src/arm/DD-PPS.dtbo /lib/firmware

4. Edit /boot/uEnv.txt:

###Overide capes with eeprom
uboot_overlay_addr0=/lib/firmware/BB-I2C2-RTC-DS3231.dtbo
uboot_overlay_addr1=/lib/firmware/BB-UART4-00A0.dtbo
uboot_overlay_addr2=/lib/firmware/DD-PPS.dtbo

5. Reboot to apply changes.

6. Setup GPSd

• Edit /etc/default/gpsd. Use file in this repo as reference.

• Start GPSd:

  sudo systemctl start gpsd
  sudo systemctl enable gpsd
  systemctl status gpsd

• Check using gpsmon and cgps commands.

6. Setup Chrony

• Edit Chrony config files. Use file in this repo as reference.

• Start GPSd:

  sudo systemctl start chrony
  systemctl status chrony

• Check using chronyc tracking, chronyc sources -v, and chronyc sourcestats -v commands.

7. (Optional) Setup nginx + php to serve /var/www/html.

Photos

Time Page

This is the html website included in this repo. In concept, it is similar to time.is.

References

My setup is based off the following guides, very thankful for them.

• https://austinsnerdythings.com/2021/04/19/microsecond-accurate-ntp-with-a-raspberry-pi-and-pps-gps/
• https://robrobinette.com/pi_GPS_PPS_Time_Server.htm
• http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html