Hardware | 2x Edimax BR-6104KP |
GPS Board/PPS Source | Motorola Oncore UT+ |
Linux Kernel | 2.6.24.2 |
LinuxPPS | 5.1.0 ntp-pps-2.6.24-ter.diff |
NTP | 4.2.4p4@1.1520 |
This is a short description how I managed to setup cheap and fairly accurate NTP server
using LinuxPPS on an Edimax BR-6104KP.
Both Edmiax routers are using the same PPS signal. A 74HC00 shifts 5V level to 3V3:
mknod -m 0644 /dev/pps0 c 253 0 mknod -m 0644 /dev/pps1 c 253 1Following modules must be loaded for PPS on DCD:
root@OpenWrt:~# lsmod Module Size Used by Not tainted amba_pl010 4464 2 serial_core 16928 2 amba_pl010 pps_core 5968 3 amba_pl010,serial_core ipv6 237264 18or
root@OpenWrt:~# lsmod Module Size Used by Not tainted pps_gpio2 976 1 pps_core 5968 2 pps_gpio2 ipv6 237264 18for PPS on GPIO2. Use ppstest (install with ipkg) to check.
Add following entries to your ntp.conf:
# Atom PPS Clock Discipline driver 22 on /dev/pps0 server 127.127.22.0 minpoll 4 maxpoll 4 fudge 127.127.22.0 flag2 0
Sure: This is not a perfect Startum 1 server due to "high" offset and jitter.
The setup is in my garage so environment temperature is variying from 15°C to 40°C:
Outlook
I will try to use the new LinuxPPS code with "ldisc". Tweaks could be done
using a more stable quartz or clock. Probably using Adm5120 FIQ instead of
normal IRQ could reduce jitter and offset.
I am going to ask bifferos@@@yahoo.co.uk to add my patches.