This document is intended to be a quick guide for how to build your own compact GPS NTP server using a Motorola Oncore timing GPS receiver (VP/UT), Soekris net4801, and FreeBSD 9 or 10.
|Item||Approx. cost, USD|
|Soekris NET4801, used, with case||$50|
|Motorola Oncore VP/UT+||$30|
|MCX <-> Female SMA bulkhead pigtail||$5|
|5v GPS Antenna||$15|
|4-8G CF Card||$15|
|Set of 0.1" header jumpers||$5|
|2G CF Card||$10|
|PCB standoffs and screws||$5|
|net4801 JP4||net4801 JP5||Oncore J1||Color|
|NC||01 (+3.3 VDC)||01 (Bat)||Yellow|
|NC||02 (+5 VDC)||02 (+5 VDC)||Red|
|N||11 (GND)||03 (GND)||Black|
|01 (DCD*)||03 (GPIO0*)||06 (1PPS)||Orange|
|05 (GND)||NC||07 (1PPS RTN)||Gray|
|NC||18 (TTL RXD)||08 (TTL TXD1)||Blue|
|NC||19 (TTL TXD)||09 (TTL RXD1)||Green|
|NC||20 (TTL GND)||10 (TTL RTN)||White|
If you have no PXE environment, use a CF<->USB adapter and write the FreeBSD USB memstick image to the smaller CF card using another host. This step is necessary because comBIOS cannot boot from USB.
Install the CF card into the Soekris, and then connect the larger (target) CF card to the Soekris via the USB<->CF adapter.
The following parameters will need to be set via the loader to install, subsequently on the system for it to boot without panicing.
kern.cam.ctl.disable=1 vm.kmem_size_scale=1 hw.ata.ata_dma=0 console="comconsole"
These can be set in /boot/device.hints and /boot/loader.conf on the install media if you have another FreeBSD host available.
Boot and install the system to the target disk, and include source if you wish to recompile the kernel. Before quitting the installer, make the same changes as above, in /boot/device.hints, and /boot/loader.conf, and don't forget to rename the root partition in /etc/fstab so it boots normally from ada0 (If you installed via USB, it will be configured for ad0, which will no longer be true after the CF cards are swapped.)
You should also set the following:
In /etc/ttys, change the console entry to read:
console "/usr/libexec/getty Pc" vt100 on secure
In /etc/rc.conf, ensure the following are set:
sshd_enable="YES" ntpd_enable="YES" dumpdev="NO" sendmail_submit_enable="NO" sendmail_msp_queue_enable="NO"
And finally, if you're intending on rebuilding your kernel (recommended to reclaim about 10M of DRAM on this 128M platform), set the following in /etc/make.conf (this is needed to prevent the kernel compilation process from building unselected items as modules, which will take several hours on a net4801.):
Then shutdown the system, move the CF card from the USB adapter to the internal slot, and boot normally.
Here is a NET4801 kernel configuration file for 9.x Remove options ATA_CAM if you're building a new 10.x kernel: /usr/src/sys/i386/conf/NET4801
Add the following to /etc/devfs.conf:
link cuau1 oncore.serial.0 link cuau1 oncore.pps.0
NTP is available from support.ntp.org, download a current (development) version of ntpd 4.2.7, and run configure with the following parameters:
./configure --prefix=/usr --enable-debugging --enable-ONCORE --enable-SHM --with-crypto --enable-autokey --enable-ipv6
With that built and installed, here is a simple /etc/ntp.conf
# Drift cache driftfile /etc/ntp/ntp.drift # Statistics logging statsdir /var/log/ntpstats/ statistics loopstats peerstats clockstats filegen loopstats file loopstats type day enable filegen peerstats file peerstats type day enable filegen clockstats file clockstats type day enable # Servers and Peers server ntp-nist.ldsbc.edu server montpelier.caltech.edu server tick.ucla.edu # Reference Clocks # Motorola Oncore/PPS server 127.127.30.0 prefer minpoll 16 maxpoll 16 fudge 127.127.30.0 time1 0.000 # Permit chimes, but not monitoring restrict -4 ntp-nist.ldsbc.edu notrap nomodify nopeer restrict -6 ntp-nist.ldsbc.edu notrap nomodify nopeer restrict -4 montpelier.caltech.edu notrap nomodify nopeer restrict -6 montpelier.caltech.edu notrap nomodify nopeer restrict -4 tick.ucla.edu notrap nomodify nopeer restrict -6 tick.ucla.edu notrap nomodify nopeer restrict -4 default notrap nomodify noquery nopeer restrict -6 default notrap nomodify noquery nopeer # Localhost restrict 127.0.0.1 restrict ::1
And /etc/ntp.oncore0 (You can start in mode 4, give it lots of time to survey your position, or skip this step by using a handheld GPS or your phone to get your location for configuration purposes.):
# /etc/ntp.oncore0 # # Reference Clock configuration for Motorola Oncore UT+ # # Five Choices for MODE # (0) ONCORE is preinitialized, don't do anything to change it. # nb, DON'T set 0D mode, DON'T set Delay, position... # (1) NO RESET, Read Position, delays from data file, lock it in, go to 0D mode. # (2) NO RESET, Read Delays from data file, do SITE SURVEY to get position, # lock this in, go to 0D mode. # (3) HARD RESET, Read Position, delays from data file, lock it in, go to 0D mode. # (4) HARD RESET, Read Delays from data file, do SITE SURVEY to get position, # [SITE SURVEY] #MODE 1 # NB. If a POSITION is specified in the config file with mode=(2,4) # then this position is set as the INITIAL position of the ONCORE. # This can reduce the time to first fix. MODE 1 LAT 33 29.00000 # + == North LONG -112 0.00000 # - == West HT 340.00 # GPS height, meters ASSERT HARDPPS MASK 10 # Elevation mask, degrees SHMEM /var/log/ntpstats/oncore.0 TRAIM YES