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jks-prv / Beagle_SDR_GPS

KiwiSDR: BeagleBone web-accessible shortwave receiver and software-defined GPS (archived)
http://kiwisdr.com
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GPS increase SPI speed #146

Closed jackobian closed 6 years ago

jackobian commented 6 years ago

As i see from code of solve() function the main execution time is in loadrelpica() function. i follow it and found that something related to spi which is 8M speed, if i increase that speed to 125M can i get high update rate of gps solution

jks-prv commented 6 years ago

Where did you see a reference to 8 MHz SPI? Are you looking at my sdgps project sources or the new Beagle_GPS sources? I forget what sdgps used but Beagle_GPS runs the SPI at 48 MHz just like the KiwiSDR project.

But this will make no difference to the rate of GPS solutions. That is determined by the "TaskSleepMsec(4000);" in SolveTask() of either project. This will limit the GPS solutions to 0.25 Hz (once every 4 seconds maximum). I don't know why Andrew has limited the solution rate in this way. You could try decreasing the delay and see if the quality of the solutions remains the same.

Remember that this GPS code is very basic. You should not expect to get the high solution rate (e.g. 10 Hz) of commercial GPS receiver that have had many years of careful optimization.

jackobian commented 6 years ago

Sorry i miss the number it is 48Mhz

On Sun, Jan 28, 2018 at 11:18 PM, John Seamons notifications@github.com wrote:

Where did you see a reference to 8 MHz SPI? Are you looking at my sdgps project sources or the new Beagle_GPS sources? I forget what sdgps used but Beagle_GPS runs the SPI at 48 MHz.

But this will make no difference to the rate of GPS solutions. That is determined by the "TaskSleepMsec(4000);" in SolveTask() of either project. This will limit the GPS solutions to 0.25 Hz (once every 4 seconds maximum). I don't know why Andrew has limited the solution rate in this way. You could try decreasing the delay and see if the quality of the solutions remains the same.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/jks-prv/Beagle_SDR_GPS/issues/146#issuecomment-361096883, or mute the thread https://github.com/notifications/unsubscribe-auth/AIO0smsYjGP9Y7xH5kMi2KuGW_SYDIeZks5tPOQ0gaJpZM4Rv0sD .

jks-prv commented 6 years ago

It's okay. The questions of solution rate speed improvement and accuracy improvement are very interesting and worthy of investigation.

Sometime, tell us about your progress with porting to the Zynq platform.