I know this is going back a bit but I would like to do the same thing for my Gnuradio satellite ground station. I was actually tempted to compile satellite tracking into a Gnuradio block. One you could simply use in a flowchart without any of the messing about with XMLRPC but like my new hexagonal wheel project, with active compensatory suspension, it might be better to use what’s already there.
Did anyone do this? And, how difficult would it be in practice to develop a native block that either contains predict, or accesses it? Possibly not very difficult at all and maybe already done?
Mike
On 22/07/13 12:31, M Dammer wrote:
Is it possible to link Gnuradio and Gpredict ? I want to use Gpredict as
tracker controlling the antenna position and to pass doppler corrected
frequency data to Gnuradio.
In a word, yes.
Can be very simple. I did it by using an XML Server in the flow graph,
and wrote a quick XML client (actually I "stole" most of it from an
example), and sent the doppler info from predict via a variable.
doppler info was received from predict using some code to query predict
using UDP. I think I just used nc to send the UDP query to predict,
recovered the shift from the reply, and sent it back to the XML Server
running within the flow graph.
Unfortunately I can't find my actual code right now, but I literally
copied an example, and added the UDP Predict clients bit. It went
something like this pseudo code (Yes, this is a mix of shell,and
python, and you need to re-write the getting doppler from predict yourself, but you get the idea, and should give you enough)
import time
import sys
from socket import *
import xmlrpclib
import binascii
s = xmlrpclib.Server("http://192.168.39.74:8081";)infinite=1
while infinite == 1;
# Grab predict doppler using UDP
DOPPLER=`nc -u -s 2 $PREDICTHOST GET_DOPPLER $NORAD_NUMBER`
s.set_doppler_shift($DOPPLER)
time.sleep(1)
The variable (lets call it doppler_shift) exists in the flowgraph,
and was multiplied appropriately and applied to the centre frequency of
a FIR filter.
You can pretty much pass any information you want in and out of a flow
graph using a XML Server/Client pair. I've done TX/RX switching, and
am currently working on telemetry decoding/display
Iain