What is it?

This program enables you to connect a GPS module with PPS signal (or any other PPS source) to a Linux system with GPIO pins and then interface this PPS signal to NTP. This can give you very accurate timekeeping; on your local computer or maybe even multiple computers on your LAN.
When you use this program you do not need to patch the kernel to get PPS support, you also do not need to patch the NTP program.

David Taylor has an excellent description how to get it to work.

Originally this program was written for the Raspberry Pi but other systems (like the UDOO, the Nanos G20, BeagleBone, CubieBoard and the GL-iNet) are known to work as well.


Download link:rpi_gpio_ntp-1.1.tgz
Download link:rpi_gpio_ntp-0.6.tgz
Download link:rpi_gpio_ntp-0.5.tgz


1.1improved cpu usage on systems that use polling (GL-iNet) / support for unexpected /sys filesystem layouts (CubieBoard))
1.0this version can now also do its job on systems with gpio pins that don't trigger an interrupt (e.g. GL-iNet) albeit with heavy cpu usage (polling!)
0.6handle GPIO pins that cannot discriminated between rising and falling / prevent spurious wake-ups (causing high cpu load)
0.5shortened the hot code paths
0.3improved manual, bugfix for fudge factor
0.2can now toggle an other GPIO pin so that you can follow things using an oscilloscope
0.1initial release


jitter over 8192 seconds

offset over 8192 seconds

allan deviation over 8 days of data

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