This page serves as a descriptor of how the software is configured on the TimeHat SD card as of 03/2025. Made for the Pi3b and 4b. (Will be testing and adding support for other Raspberry Pi models as time allows, and as interest is shown).

• RV-3032-c7 Version

Software Info

• The operating system is Raspbian Lite (64bit)
• Key software conponents:
  • chrony - NTP client & server
  • gpsd - communicates with and configures the GNSS receiver, sends time data to chrony
  • lighttpd - web server for status page
  • sshd - remote access over secure shell

Hardware Info

• CPU locked to 1GHz to minimize jitter and heat
• GNSS receiver connected to ttyAMA0
• RTC (DS3131 or RV-3032-c7) connect to i2c bus
• WiFi and Bluetooth disabled to save power. Also WiFi is generally too unstable for use as a network time server.
• RAM usage is minimal, any Pi can run this setup, adding more RAM will not improve performance.

/boot/firmware/config.txt

# For more options and information see
# http://rptl.io/configtxt
# Some settings may impact device functionality. See link above for details
 
dtparam=i2c_arm=on
dtoverlay=i2c-rtc,rv3032
dtparam=backup-switchover-mode=1
 
arm_64bit=1
 
[all]
enable_uart=1
dtoverlay=disable-wifi
dtoverlay=disable-bt
dtoverlay=pps-gpio,gpiopin=4
dtparam=act_led_trigger=heartbeat
 
disable_fw_kms_setup=1
auto_initramfs=1
#disable_poe_fan=1
#force_eeprom_read=0
#ignore_lcd=1
 
arm_boost=0
arm_freq=1000
force_turbo=1