OpenwebRX and ZMQ approach

[diazm]

Hi, I'm trying to use OpenwebRX wih GNURadio and ZMQ PUB/SUB. My goal is to replace FIFO and all the TCP stuff for ZMQ . In my first approach I add the ZMQ PUB SINK block with address 'ipc:///tmp/fifo-pipe' to the flowgraph in GNURadio-Companion keeping the FIFO (GNURadio File sink block).
Then in csdr.py changed the variable any_chain_base = "nc -v 127.0.0.1 {nc_port} | " for any_chain_base = "zmqc SUB -rc 'ipc:///tmp/fifo-pipe' | "

Execute openwebrx.py and all I get in the browser is a white screen in FFT getting network usage, server CPU and all others status variables.

Any ideas?

[ha7ilm]

What does this output?

zmqc SUB -rc 'ipc:///tmp/fifo-pipe' | csdr through >/dev/null

[diazm]

Hi András

zmqc SUB -rc 'ipc:///tmp/fifo-pipe'

is like netcat for ZMQ. I got it from https://github.com/zacharyvoase/zmqc
but analyzing outputs from ZMQC and netcat they are slightly different.

Also I am testing with GNURadio models from CSDR library in particular with test_fft_grc.grc:

I got this output, with the expected behavior:

After I try this model:

I got this output but the behavior is unexpected:

I really don`t know why is a different behavior with the GNURadio ZMQ-SUB block and the ZMQC-SUB from the console.

[ha7ilm]

What is the data type of the output of zmqc?

csdr has some diagnostic functions like dump_f and dump_u8 that you can use to check if the type that you guess is valid. You also need to adjust the format_conversion parameter in the config accordingly. Another tool that you can use to view the raw data: od. Just make sure that you use a pager (like less) or head so that your screen isn't filled with text.

[diazm]

OK, I checked the output data with this small python program:

from gnuradio import analog
from gnuradio import blocks
from gnuradio import gr
from gnuradio import zeromq
import zmq
import array

socket_str = "tcp://127.0.0.1:5557"


def zmq_consumer():
    context = zmq.Context()
    results_receiver = context.socket(zmq.PULL)
    results_receiver.connect(socket_str)
    while True:
        # pull in raw binary data
        raw_data = results_receiver.recv()
        print raw_data
        # convert to an array of floats
        #float_list = array.array('f', raw_data) # struct.unpack will be faster
        # print flowgraph data
        #for signal_val in float_list:
        #    print signal_val


# build simple flowgraph that outputs a repeating ramp from 0 to 1
class simple_flowgraph(gr.top_block):
    def __init__(self):

        gr.top_block.__init__(self)

        samp_rate = 4000 #32000.0

        # generate repeating ramp from 0 to 1
        self.analog_sig_source_x_0 = analog.sig_source_f(
            samp_rate,
            analog.GR_SAW_WAVE,
            1e3,
            1,
            0)
        self.blocks_throttle_0 = blocks.throttle(
            gr.sizeof_float*1,
            samp_rate,
            True)
        self.zeromq_push_sink_0 = zeromq.push_sink(gr.sizeof_float,
                                                   1,
                                                   socket_str,
                                                   100,
                                                   False,
                                                   -1)

        self.blocks_file_sink_0 = blocks.file_sink(gr.sizeof_float * 1, '/tmp/osmocom_fifo', False)


        ##################################################
        # Connections
        ##################################################
        self.connect(
            (self.analog_sig_source_x_0, 0),
            (self.blocks_throttle_0, 0)
        )
        self.connect(
            (self.blocks_throttle_0, 0),
            (self.zeromq_push_sink_0, 0)
        )
        self.connect((self.blocks_throttle_0, 0), (self.blocks_file_sink_0, 0))

# instantiate and start the flowgraph
flowgraph = simple_flowgraph()
flowgraph.start()

# start the receiver socket
zmq_consumer()

It is a GNURadio flowgraph with a signal source connected to a FIFO and to ZMQ PUSH Sink block.
The function zmq_consumer() is ZMQ PULL (not GNURadio block) that read the ZMQ PUSH block.

If you execute the code program.py | csdr dump_f and in other terminal check the FIFO cat /tmp/osmocom_fifo | csdr dump_f you will see that the ZMQ output add some kind of garbage to the real data, that I assume is the FIFO output.
Maybe I have a mistake with the raw_data variable format and that`s why the output is not correct. Any ideas?