hello niall99,
did you confirm you’ve compile the device tree, and it’s loaded correctly.
you may push the binary to the target, and specify the path to the FDT entry in the /boot/extlinux/extlinux.conf.
besides,
if you’re using GPIO pins under AON category to feed PPS signals, you may also use low-level APIs to capture timestamps for system synchronization.
please also check this thread, Jetson Xavier hardware pps_out - #16 by shgarg for reference,
thanks