Well, I have gone to multiple propellers. Good thing I have a multi-engine rating.
I have been working on implementing satellite tracking algorithms (SGP4) on the propeller device as previously posted. I now have a new propeller board that I will be using to drive az/el servos to move an antenna in sync with a satellite pass. This little board can be used drive up to 16 servo motors. If you need more than this, you can daisy-chain two of them together and control up to 32 servos. (I foresee an atonomous flying vehicle in my future, but that is another post for another day...)
I am working with small hobby servos that are capable of moving up to 8 lb of antenna hardware. The pan mount can take 150 lb on top of the mount and 200 lb of side load at the shaft. The tilt mount can handle 8 lb of load.
This is sufficient for my small arrow antenna which is only 20 oz and is giving me some experience in driving servo motors. I could also velcro my solar panel array to it and have it track the sun to recharge my batteries whilst operating off the grid. The pan mount can rotate up to 450 degrees while the tilt mount can rotate 135 degrees. So, this should be fun for some garden experiments with satellites as well as making a fun pan/tilt camera mount.
Future projects of course will scale this up to handle large antenna arrays.
Today I played around with my new floating point coprocessor. I decided to build a bit of code that would parse a two line Keplerian Elements.
I have built an object that will parse this data out into its constituent values using the coprocessor. The output from this test looks like this:
AO-51
1 28375U 04025K 12068.46137681 +.00000200 +00000-0 +72724-4 0 02147
2 28375 098.1341 038.4897 0084202 346.8009 013.0981 14.40905486404267
satName: AO-51
idesg: 04025K
epoch: 12068.46
xndt2o: 1.9999999E-6
xndd6o: 0.0
bstar: 7.2723999E-5
xincl: 98.134101
xnodeo: 8.4897
eo: 0.0084201993
omegao: 346.8009
xmo: 13.098098
xno: 14.409052
catnr: 2837
wlset: 0.0
revnum: 40426
It is interesting to note the effect of a 32 bit floating point value used to hold this data. Since only 7.2 significant digits are available, values like epoch have been truncated to fit in 32 bits. I parse out 12068.46 for a value that should be 12068.46137681.
At best only an approximation is going to be possible with 32 bits for SGP4 calculations, which given the beamwidth of my antennas is likely to be sufficient. In any event is is an interesting chip to work with.
With 128 floating point registers available and the ability to store user-defined functions on-chip, I am hopeful that the calculations can be done completely on-chip. In an ideal world, I would pass in the kep of the satellite of interest as a string and would get back azimuth, elevation, aquisition/loss of signal times, etc. In a more ideal world, I would get back only the necessary information to move an az/el rotor system to the correct point in space. We shall see how it goes...
