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.