How to log raw IQ data from Raspberry Pi 4 over eth0 to PC?

huuhung032 · April 16, 2025, 2:33pm

Hi everyone,

I’m working with a KrakenSDR (5-channel RTL-SDR array) connected to a Raspberry Pi 4 running the standard firmware. I’d like to capture the raw IQ data (after FIR decimation and optional IQ calibration) and stream it over Ethernet (eth0) directly to my PC for further offline processing.

Could you help me with:

The proper way to redirect IQ data (complex float32) to the Ethernet interface from the Pi?
What configuration files or blocks (in daq_chain_config.ini or otherwise) I need to modify?
How do I receive and log this data on the PC? (e.g., netcat, Python socket, etc.)

I saw mentions of the IQ Server block and shared memory, but not sure how to access the streamed data remotely.

Any advice, script examples, or best practices would be greatly appreciated. Thanks!

krakenrf_carl · April 17, 2025, 1:58am

Hi, the best way would be look at how it’s done on our gr-krakensdr GNU Radio block.

github.com/krakenrf/gr-krakensdr

python/krakensdr/krakensdr_source.py

main

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2022 KrakenRF Inc.
#
# SPDX-License-Identifier: GPL-3.0-or-later
#


import numpy as np
import socket
import _thread
import queue
from threading import Thread
from threading import Lock
from gnuradio import gr

from struct import pack,unpack
import sys

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Basically the steps are:

Set heimdall_daq data_interface out_data_iface_type = eth;
In your custom PC software, set up a TCP socket connection and receive the data into a buffer.
Process the received data frames, splitting them up into the individual channels and header metadata. (As shown in the GNU Radio code)

huuhung032 · April 17, 2025, 7:52am

When logging IQ data with Heimdall IQ recorder, which antenna channel(s) does the recorded data represent in the 5-antenna array?

krakenrf_carl · April 26, 2025, 1:10am

They should correspond to the physical labels on the device.