Overview

Before installing ChroGPS Dash, you need a working GPS/NTP stack: GPSd receiving position and timing data from your GNSS receiver, and Chrony disciplined by that data. The hardware provisioning script builds this stack for you automatically, handling package installation, device configuration, and Chrony refclock setup.

Two GNSS connection modes are supported:

Hardware Provisioning

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash

You can also pass flags to skip auto-detection and force a specific configuration:

# GPIO mode (Raspberry Pi + GNSS HAT), default GPIO pin 18:
curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode gpio

# GPIO mode with a specific PPS GPIO pin:
curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode gpio --gpio 4

# USB mode (auto-detect device):
curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode usb

# USB mode with a specific device path:
curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode usb --device /dev/ttyACM0

What the script provisions

All modes:

• Installs: gpsd, gpsd-clients, chrony, pps-tools
• Configures /etc/default/gpsd for your GNSS device
• Configures Chrony refclocks appropriate for the mode
• Enables gpsd.socket, gpsd, and chrony to start at boot

GPIO mode (Raspberry Pi only) — additionally:

• Adds to /boot[/firmware]/config.txt:
  • enable_uart=1 — enables the hardware UART
  • dtoverlay=disable-bt — disables Bluetooth on Pi 3/4/Zero W/Zero 2W, which would otherwise occupy the reliable PL011 UART and force the GPS onto the unreliable mini-UART
  • dtoverlay=pps-gpio,gpiopin=N — exposes the PPS signal from the HAT as /dev/pps0
• Removes the serial console from cmdline.txt (backed up as cmdline.txt.bak) so GPSd can own the UART
• Masks serial-getty@ttyS0 and serial-getty@ttyAMA0 to prevent conflicts
• Creates /etc/modules-load.d/pps-gpio.conf so the pps-gpio kernel module loads at boot
• Configures Chrony with SHM 0 noselect (NMEA used only as a lock anchor) + PPS /dev/pps0 lock GPS prefer (PPS drives synchronization)

USB mode — additionally:

• Configures Chrony with SHM 0 (NMEA disciplines the clock, with offset 0.5 to compensate for USB latency)
• Restarts GPSd and Chrony immediately — no reboot needed

GPIO mode: reboot required

sudo reboot

Once provisioning completes, the script will prompt whether you want to install ChroGPS Dash. If you choose yes, the dashboard installer runs automatically — no need to run a separate command. If you are in GPIO mode and install before rebooting, the dashboard installer will show a yellow advisory message about the deferred Chrony restart — this is expected. Everything will work after reboot.

Verifying the setup (after reboot)

After rebooting a GPIO mode system, verify the stack:

# PPS device is present:
ls -l /dev/pps0

# Confirm pps-gpio and disable-bt overlays loaded:
dtoverlay -l

# GPSd has a fix and is receiving data:
gpsmon

# Chrony sees the GPS/PPS refclocks:
chronyc sources -v

# Chrony is synchronized and stable:
chronyc tracking

In chronyc sources, a healthy GPIO/PPS setup shows two refclock lines. The NMEA source will be marked ? or x (used only as a lock anchor, not a sync source), while the PPS source will be marked * (the active sync source).

For USB mode, skip the pps0 and dtoverlay checks — just verify GPSd is receiving data and Chrony shows the NMEA refclock marked *.

Removing Hardware Provisioning

To fully reverse everything the provisioning script configured:

curl -fsSL https://chro.gpsda.sh/hardware-uninit | sudo bash

The removal script:

• Stops and disables gpsd.socket, gpsd, and chrony
• Purges pps-tools, gpsd, gpsd-clients, and chrony (including their configs)
• GPIO mode: removes all entries added to config.txt, restores cmdline.txt from the .bak backup, unmasks serial-getty units, and removes the pps-gpio module load config
• Prompts whether to also uninstall the ChroGPS Dash web dashboard

Command Reference

hardware-init — Provisioning Script

Examples:

Auto-detect and provision:

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash

GPIO mode, default PPS pin (18):

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode gpio

GPIO mode, custom PPS pin:

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode gpio --gpio 4

USB mode, auto-detect device:

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode usb

USB mode, specific device path:

curl -fsSL https://chro.gpsda.sh/hardware-init | sudo bash -s -- --mode usb --device /dev/ttyACM0

hardware-uninit — Removal Script

The removal script takes no flags. It detects what the init script provisioned and prompts for confirmation before removing anything.

curl -fsSL https://chro.gpsda.sh/hardware-uninit | sudo bash

Supported Platforms

*GPIO mode requires Raspberry Pi Device Tree infrastructure (config.txt, dtoverlay). It is only supported on Raspberry Pi hardware.