[Discuss-gnuradio] New/Updated GPredict Interfacing Blocks

Hi everyone,

I've been doing a good bit of satellite work and had the need to blow the dust off of a discontinued gr-gpredict-doppler  OOT module and enhance it.  The goal was to have a state value to pass in and key off of gpredict's perspective of if the satellite was visible or not for recording purposes (better yet preventing huge blind-saving files), and to better pass the doppler frequency through to GNURadio.  So I've forked it (https://github.com/ghostop14/gr-gpredict-doppler.git)  and added a bunch of new features:

doppler block:

  -  Now adds freq output block to make it compatible with other message blocks like the USRP source

- Now supports AOS / LOS commands from gpredict - a state output message block compatible with all of the state inputs in the gr-filerepeater block is also produced.  Result: A file record can be triggered to start when a satellite is in range, then automatically closed when it goes out of range.

 -  Enhanced the gqrx / gpredict radio control command handling to handle additional messages and correctly handle exit

[new] rotor block:

  - Accepts inputs from  rotctl / gpredict's rotor control.

  - Az/El are passed in, interpreted, and packed in an output message with 'az' and 'el' meta keys

  - A basic minimum elevation is added to the block where if the elevation is > min, an optional state output is produced (1= >= min, 0 is below min).  Again this can be used with the gr-filerepeater adv sink

[new] az el limit block:

  - Allows az/el min/max values to be set.  If the rotor block output az_el is fed into this block, an output state message is produced for "inside the az/el limits" / outside the az/el limits.  Again, this can interface with the file blocks

gr-filerepeater (https://github.com/ghostop14/gr-filerepeater.git) has also gotten a lot of enhancements to help with controlling unsupervised file writes.  The concept of this state 1/0 has worked its way through for easy file write control.  The file sink can also now extract/save message-based data in exactly the same way streaming data was handled.

Anyway let me know if there's any other enhancement requests or if you run into any new issues.

Enjoy!