My Proposed Instrument Experiment

I like instruments on a race boat and find their feedback very useful. They help the skipper/helmsmen validate whether their vessel is at optimal performance in the conditions being faced. Throughout the 2013 season I noticed that my NMEA instrument display was failing. It worked for about 5 minutes then froze and required a power off/power on cycle...not very reliable. Over the winter months, I've tested and determined that the central computer of my NMEA instrument panel has an electrical short (somewhere within the curcuitry). Emails to the gentlemen that installed my unit have gone unrepresented. Time to seek out new options.

I received an Android Galaxy Tab 2 7" for Christmas. This little device has built in GPS and bluetooth and has a large screen display. Its good for web stuff and my daughters games while on the road.

I started to devise a plan to see if I could use this little device as a NMEA repeater. If I wanted to use the tablet I would have to:

1. prove suitability/usability on board
2. Determine how NMEA data would get to the tablet
3. Write an Android program to repeat the data

1. to determine suitability/usability on board, my requirements were:
a) must be mounted
b) must use a protective case (the case must handle the elements, rain, splashing, hail, sun. Options here are to either buy or make a waterproof case. Nothing really fits this requirement on the market that is mountable. Because this use case is very specific, it looks like making a case may be the only option).
c) must be able to interface with touch features, either physically with finger (case must allow touch options through the protective display cover) or remotely via another device (using remote control apps for Android). My touch requirement may not be possible.
d) mounted to the mast, just below the boom for all crew to see
e) must show at least 1 instruments data in the display, for starter Wind speed and direction.

2. How to get NMEA to tablet. In my case, I have 2 instruments onboard. The first is a NMEA based wind instrument, the second is a water speed instrument. Upon further discovery I've found that the water speed instrument doesn't output NMEA based signals. I did this my hooking up my boat devices to a USB to serial interface cable and outputted the instrument data to a PC Serial data logger. NMEA signals are transmitted via serial protocols, to be more specific RS-232 protocol. RS-232 protocol is essentially serial based ASCII signals sent as bytes and transmitted over wires using positive and negative DC voltage. The challenge here is to get the serial data signals from the wind instrument forwarding to the tablets bluetooth device. If I can figure out how to get this converted, then we're off to the races.

3. I'm a software developer, so writing Android programs to interface with bluetooth and the resulting NMEA data should be fairly straight forward. Something that shows wind speed and direction in a simple Android app will do nicely.

With all these pieces in play, there might be a solution here, or maybe not.

Neil