GPSDO Time reference project progressing




The Thunderbolt Trimble arrived during the week, and after 48 hours for the self survey and to calibrate the internal PID loops its delivering a nice level of performance, the only disagreement with my HP 5335 Counter is down in the 10E-15 territory which is outside the resolution of this GPSDO.

The entire ensemble is, however, untidy.  The GPS unit itself is in a small metal box, I have an external laptop power supply to provide the required voltage levels, serial connections, antenna connection, and then the outputs… untidy.   It gets worse when I run a serial cable to monitor it via Lady Heather or similar.

I want to be able to leave this system running all the time, so it needs to go in a box and include its own monitoring.  I also don’t want to spend a fortune here but I also wanted rack mount, and sometimes things just work out with a 2RU rackmount PLA project box at the local Jaycar for $20 😉

The internals for the box are mostly coming out of my ‘junk’ box, bits and peices I’ve collected over the years, including:

* Beaglebone Black

This board will be used to ‘monitor’ the GPS unit and provide network connectivity for ntp etc.   This board will also run the display, keypad, etc so I can monitor the system without using an external PC.

* USB to Serial converter.

An old prolific (PL2303) USB<->Serial converter will be used, while strictly not necessary it removes the need for level conversions here and the BBB has a usb port readily available.

* CM12864-2 128×64 White on Blue Graphical LCD bought for a project several years ago and never used.   This will make a nice display for this project.

* 16 character keypad picked up at a field day somewhere.  I don’t _need_ 16 keys, but it looks ok and will support any additional functionlity I may add later.   Its been sitting in a drawer for years so the price is right 😉

*Amphenol case mount BNC connectors, I picked up a box of ~20 of these for $2 at a field day recently.

* level converters should these be necessary, I suspect they won’t be needed.

I have ordered on additional item:

Sparkfun Graph LCD serial backpack for the display, simply because this will be more convenient wiring the display up to the BBB.

The next steps:

* Code up a parser for the messaging coming from the GPS.

* Wire up the keypad and code up a driver using GPIO pins.

* Wire up the display and see if I can find a driver somewhere, I suspect I can.

* Code away.

all up the boxing project will cost approximately $50 out of pocket given I already have all the key components, and $30 of that is the backpack for the LCD panel to save some time.