Doing it the way Marcus M. described wasn actually not that complicated
as I expected. I have a small "Embedded Python Block" that does more or
less what I need. The file is attached, if anyone else needs this :)
The error handling is a bit rough and there are probably many things to
improve on, but its a starting point.
Am 07.05.23 um 13:09 schrieb Fabian Schwartau:
Hi again,
as I described earlier, I am now using a "Tags Strobe" block to
periodically tag the data with the current gps coordinates. Within the
"Tag Strobes" I use a function call to create the value:
pmt.to_pmt(gps.get_current_gps_position())
And this function is defined in a "Python Module" block.
But it seems that the function is only called once at startup and then
never again. Which is quite useless in my case. Is that correct? Is
there any other easy way to get the gps data into a stream as tags
within GRC? I am not familiar with programming my own blocks and I don't
see myself capable of doing what Marcus M. suggested earier, without
spending a considerable amount of time.
Best,
Fabian
Am 05.05.23 um 09:58 schrieb Marcus Müller:
Hi Fabian,
it's interleaved real, imag, real, imag. If you used
dtype=np.complex64 instead of float32 (and then not double the count),
you'd get it interpreted exactly that way :)
Cheers,
Marcus
On 04.05.23 19:38, Fabian Schwartau wrote:
Sorry again, never mind... I found the problem.
The source code for reading the data does not include the fact that I
am reading complex data and also three streams. Change the one line to:
data=np.fromfile(file=fh, dtype=np.float32,
count=3*2*int(header_info['nitems']), sep='', offset=0)
and everything seems to work as expected. Now I just have to figure
out how the data is ordered in that blob ;)
Best,
Fabian
Am 04.05.23 um 19:19 schrieb Fabian Schwartau:
Hi everyone,
I think I got hit by https://github.com/gnuradio/gnuradio/issues/5568.
Exactly the same error message. Is there any update on that issue or
a workaround?
Attached are my files.
Best,
Fabian
Am 03.05.23 um 21:01 schrieb Marcus D. Leech:
On 03/05/2023 14:59, Fabian Schwartau wrote:
Sorry, forget it. Wrong sink...
You probably want:
https://wiki.gnuradio.org/index.php/File_Meta_Sink
Am 03.05.23 um 20:52 schrieb Fabian Schwartau:
OK, I think I found an easier way (at least for me), without
having to write my own module - never done that.
I used the "Tags Strobe" block in combination with the "Python
Module" for my gps_get_position() function.
Anyway, where can I find a definition of the format of the
"Tagged File Sink"? I need to read this with antoher program,
without gnuradio, but in python.
Best,
Fabian
Am 03.05.23 um 20:04 schrieb Marcus Müller:
Hi Fabian,
I'd write a block that copies a stream in- to output. It might
query gpsd every time the work() function is called, or have a
FIFO into which data from gspd is being pushed by a separate
thread (or by reading from a socket or however gspd works, I
must admit I'm not sure).
You then take that info, and encode the long, lat, uncertainty
as (double, double, double) PMT tuple. You then use add_item_tag
to add that PMT to the first sample in your output buffer.
You'd feed the result into a metadata file sink block: That
saves things in a serialized format ready for retrieval.
Best,
Marcus
On 5/3/23 19:52, Fabian Schwartau wrote:
Hi everyone,
I am trying to record some data from an SDR and would like to
sync/tag the data with the current gps position from gpsd. I am
kind of stuck and don't know how a possible solution for that
might look like in grc.
I have a python function that gets the current position as a
tuple, but how do I get this into my data stream, which I would
like to write to a CSV file or similar?
I am not asking for a solution of my problem, just point me in
the right direction ;)
Best,
Fabian
"""
GPS Tagger:
Add a GPS tag every second to the stream
"""
import numpy as np
from gnuradio import gr
import gpsd
import time
import pmt
class blk(gr.sync_block):
"""GPS Tagger - Add a gps tag every second"""
def __init__(self):
gr.sync_block.__init__(
self,
name='GPS Tagger',
in_sig=[np.complex64],
out_sig=[np.complex64]
)
gpsd.connect()
self.lastTime = time.monotonic()
def work(self, input_items, output_items):
timeCurrent = time.monotonic()
if timeCurrent - self.lastTime > 1.0:
key = pmt.intern("gps")
try:
packet = gpsd.get_current()
value = (packet.position()[0], packet.position()[1])
except gpsd.NoFixError:
value = (0.0, 0.0)
except:
print("GPS ERROR")
value = (0.0, 0.0)
print(value)
value = pmt.to_pmt(value)
self.add_item_tag(0, self.nitems_written(0), key, value)
self.lastTime = timeCurrent
output_items[0][:] = input_items[0]
return len(output_items[0])
