There was a request off-list for more background on this stuff, because we're using plenty of jargon. One of the big goals for this group is education, so I'm eager to help people understand what's going on. But I don't want to answer questions privately, because I'm sure more people are confused and curious.
For general context on this particular discussion, try Google searches about Software Defined Radio, and Andrew's masters thesis about GPS, which you can find along with other resources here: http://gps.psas.pdx.edu/GpsResources/ Looks like http://gnss-sdr.org and http://swiftnav.com have material that might be good too, although I haven't read any of their stuff. Let me know whether it helps you. :-) They're solving the same problems we are from different perspectives. If you want to dig into the specifics of what we're working on right now, there are four relevant git repositories at https://github.com/psas/: gps-rf-board, gps-cpld, stm32 (gpsv3 branch), and gps. The datasheet for the MAX2769 chip on the RF board is the main thing we've been struggling with lately. You might find the commit history in stm32's gpsv3 branch and in the gps repo informative for more context on what we've been doing most recently. Finally, I want to encourage everyone to ask questions, both on this mailing list and during our weekly meetings. It's super important for the future of this group that we help newer folks get comfortable participating in everything we're doing, and we can't do that if we don't know what you need. Jamey On Wed, Jun 3, 2015, 7:44 AM Kenny <ke...@romhat.net> wrote: > Into the wee hours, we kept on doing stuff. > > * Gavin and Andrew wired up the FDT custom Uninterruptible Power Supply > without melting any fingers in the process. I'm sure it was much safer > than it sounded. > * David(?) fired up the Geiger counter on picam2 and received data! So > we have another cool thing that is ready for launch. > * Kenny set up Splunk on the NUC and configured ground based systems to > do remote logging. It even integrates with Nagios so when something > goes down, the Splunk search for that host/service is a click away. > * Theo and Jamey hacked on GPS stuff > + The STM32 which controls the MAX2769 (GPS baseband receiver) now > dynamically configures the MAX according to instructions received by > debug scripts so we can test all the configurations we want without > reprogramming the STM32 each time. > + Python test scripts were overhauled to send our best known > configuration to the MAX2769 and take a short sample. Even more magic > was added to automate testing many different configurations. > + Kenny joined the party to help transmit a sweeping sine wave +/- > 2MHz around GPS baseband using HackRF. Samples received from the > MAX2769, converted and viewed in baudline showed the same sweeping sine > wave (with noise and other artifacts). This turned out to be a good way > to test poorly documented configuration settings and lay to rest > bit-order questions. > + After running through all the settings and deciding we understood > most of them to be what they should be, the correlator still wasn't able > to pick up anything in an outdoor test. > + Jamey said we could fly with this configuration and probably figure > out how to tease satellites out of the logged data later. It is > starting to look like the MAX2769 configuration is about as good as it > can get. We just need to look at the data harder. > + For fun, Kenny collected a larger sample outside from the MAX2769, > returned to the basement while converting it for GNURadio, played it > back through the HackRF in transmit mode and watched to see if the > nearby COTS GPS receiver could lock. No position lock, but I wasn't > watching the data stream to see if it was able to see any satellites at > all. Some attenuators and a direct connection might help. > > Other people did stuff too! Like rebuilding an RCS controller board and > ordering parts. I didn't keep track of all the cool things so please > correct my fumbles and add your news. > > -- > Kenny > > -+---+++-++-++++--+------+-+-++--++--+-+-++--+++-++----+-++-+++---+----+--+----+ > > > > _______________________________________________ > psas-avionics mailing list > email@example.com > http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics >
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