Congratulations to all of the GPS project contributors!!! It works! There was much squeeeeing, happy-dancing, and even some celebratory laps around the lab tonight.
At about 11pm Tuesday night, we captured a 2 minute sample of raw GPS data with the MAX2769. Based on Google Maps satellite view, the approximate coordinates of our capture location are 45.5094 N, -122.68135 W. Jamey's soft-correlator code picked out 8 satellites in the first few milliseconds of the sample. K and Jamey worked out how to provide the sample to gnss-sdr [1] and it reports position lock: Position at 2015-Jun-10 05:59:23 UTC is Lat = 45.5091 [deg], Long = -122.681 [deg], Height= 8.34588 [m] Position at 2015-Jun-10 05:59:24 UTC is Lat = 45.5093 [deg], Long = -122.681 [deg], Height= 66.1231 [m] Position at 2015-Jun-10 05:59:25 UTC is Lat = 45.5095 [deg], Long = -122.681 [deg], Height= 108.814 [m] Position at 2015-Jun-10 05:59:25 UTC is Lat = 45.5093 [deg], Long = -122.681 [deg], Height= -0.729454 [m] Position at 2015-Jun-10 05:59:26 UTC is Lat = 45.5095 [deg], Long = -122.681 [deg], Height= 33.856 [m] Position at 2015-Jun-10 05:59:26 UTC is Lat = 45.5094 [deg], Long = -122.681 [deg], Height= 20.0021 [m] Position at 2015-Jun-10 05:59:27 UTC is Lat = 45.5094 [deg], Long = -122.681 [deg], Height= -54.6768 [m] Position at 2015-Jun-10 05:59:27 UTC is Lat = 45.5094 [deg], Long = -122.681 [deg], Height= 52.3162 [m] Position at 2015-Jun-10 05:59:28 UTC is Lat = 45.5094 [deg], Long = -122.681 [deg], Height= -19.7675 [m] Position at 2015-Jun-10 05:59:28 UTC is Lat = 45.5097 [deg], Long = -122.681 [deg], Height= 43.8608 [m] Position at 2015-Jun-10 05:59:29 UTC is Lat = 45.5095 [deg], Long = -122.681 [deg], Height= -14.4595 [m] UTC 5:59 is 22:59 PDT (10:59pm -- right on time). The position wanders around a little bit, but it is definitely in the vicinity of our capture location, +/- some elevation. It is interesting to note that we did end up dropping some packets during this capture, probably because of the reduced Ethernet clock. Satellite locks near the dropped packets are not as useful for calculating location and may have negatively impacted position fix. With a little more math, we should be able to pull better location precision out of this same sample. This means we officially win. We now have a working way of recording good GPS baseband data on the rocket and we can figure out all the complex math post-processing after launch. The plan now is to build up the remaining two jGPSv3 boards on Friday with the new Venus 8 COTS GPS receiver chips Andrew tracked down. One of these will be mounted to the rocket and ready for launch. Theo is working on doing all of the magic to save the collected MAX2769 baseband data on the Flight Computer and simultaneously stream the NMEA sentences from the Venus 8 to ground. There is still a lot of board stuffing, coding and testing to do. But we can finally get all of the individual pieces working. Now it is just a matter of fitting them together. The next big question is: can we still get GPS baseband and COTS lock from the radial patch antenna when WiFi amps are on? 1. http://gnss-sdr.org/source-code -- Kenny -+---+++-++-++++--+------+-+-++--++--+-+-++--+++-++----+-++-+++---+----+--+----+
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