I'm testing the second revision of this cape now. Schematic is on github [https://github.com/ddrown/NS-T-BBB-Cape] (left: rev1, right: rev2) It's working much better than rev1, but time will tell if it has the same frequency dropouts. I've also published the NTP server status [https://github.com/ddrown/
The cape [https://blog.dan.drown.org/beaglebone-cape-for-navspark-ns-t/] has been running for 5 days now. I've been tweaking the system to see if I can get it stable. So far, the local clock looks like this: The red line shows the clock offset. When things are working properly, it's excellent.
Goal My next goal in the quest for a better NTP server is to improve the TCLKIN source. Previously, I was experimenting with TCXO's. I bought a Navspark NS-T (a timing-grade GPS receiver) and designed an adapter cape for it. This is my first time designing a circuit board, so
Starting from the previous TCXO modification [https://blog.dan.drown.org/tcxo-beaglebone-black/], I wanted to get a 24MHz TCXO working. Trial #1 I bought a set of three undocumented 24MHz TCXO's off ebay for $6. I was hoping that since they were not SMD parts, they would be easier to
I've added support for an external clock (TCLKIN) to the Beaglebone Black timer driver [https://blog.dan.drown.org/beaglebone-black-timer-capture-driver/]. Setup I used what I had on hand to test it. I setup a Navspark microcontroller to send a ~1MHz PWM (code here [http://dan.drown.org/bbb/pwm.ino.
More info on: Hardware [https://blog.dan.drown.org/beaglebone-black-gpstemperature-cape/], Kernel Driver software [https://github.com/ddrown/pps-gmtimer] The Beaglebone Black has a hardware timer capture. This means it can save the couter value at the time an input edge happens. Since it has a 24MHz clock, the timer has
I moved my Beaglebone Black GPS+Temperature [https://blog.dan.drown.org/beaglebone-black-ntpgps-server/] setup from a breadboard to a proto cape. The soldering isn't great, and the wire I had on had was much too thick for this. The back, with the DS18B20 sensor (ends up near the CPU): The
See the Part 1 of Temperature Compensation [https://blog.dan.drown.org/beaglebone-black-ntpgps-server-temperature-compensation/] or the hardware setup [https://blog.dan.drown.org/beaglebone-black-ntpgps-server/] Overview In part 1, I did a trial run of chrony's temperature compensation and got a pretty good result. In this part, I collected more data on
See also: The hardware/software setup [https://blog.dan.drown.org/beaglebone-black-ntpgps-server/] or part 2 [https://blog.dan.drown.org/beaglebone-black-ntpgps-server-temperature-compensation-part-2/] Overview Chrony (the NTP server software) has temperature compensation built in, using a quadratic forumla to estimate the effect of temperature changes have on the speed of the local
Goals I wanted to experiment with using temperature measurement to augment a NTP stratum 1 server. I started with a very similiar setup to this one [https://web.archive.org/web/20131209092059/http://the8thlayerof.net/2013/12/08/adafruit-ultimate-gps-cape-creating-custom-beaglebone-black-device-tree-overlay-file/] . [Edit: the8thlayerof.net is gone, link changed to archive.org]. This