horusdemodlib/start_rtlsdr.sh

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#!/usr/bin/env bash
#
# Horus Binary RTLSDR Helper Script
#
# Uses rtl_fm to receive a chunk of spectrum, and passes it into horus_demod.
#
# Change directory to the horusdemodlib directory.
# If running as a different user, you will need to change this line
cd /home/pi/horusdemodlib/
# Receive *centre* frequency, in Hz
# Note: The SDR will be tuned to RXBANDWIDTH/2 below this frequency.
RXFREQ=434200000
# Receiver Gain. Set this to 0 to use automatic gain control, otherwise if running a
# preamplifier, you may want to experiment with different gain settings to optimize
# your receiver setup.
# You can find what gain range is valid for your RTLSDR by running: rtl_test
GAIN=0
# Bias Tee Enable (1) or Disable (0)
BIAS=0
# Receiver PPM offset
PPM=0
# Frequency estimator bandwidth. The wider the bandwidth, the more drift and frequency error the modem can tolerate,
# but the higher the chance that the modem will lock on to a strong spurious signal.
# Note: The SDR will be tuned to RXFREQ-RXBANDWIDTH/2, and the estimator set to look at 0-RXBANDWIDTH Hz.
RXBANDWIDTH=10000
# Enable (1) or disable (0) modem statistics output.
# If enabled, modem statistics are written to stats.txt, and can be observed
# during decoding by running: tail -f stats.txt | python fskstats.py
STATS_OUTPUT=0
# Check that the horus_demod decoder has been compiled.
DECODER=./build/src/horus_demod
if [ -f "$DECODER" ]; then
echo "Found horus_demod."
else
echo "ERROR - $DECODER does not exist - have you compiled it yet?"
exit 1
fi
# Check that bc is available on the system path.
if echo "1+1" | bc > /dev/null; then
echo "Found bc."
else
echo "ERROR - Cannot find bc - Did you install it?"
exit 1
fi
# Use a local venv if it exists
VENV_DIR=venv
if [ -d "$VENV_DIR" ]; then
echo "Entering venv."
source $VENV_DIR/bin/activate
fi
# Calculate the SDR tuning frequency
SDR_RX_FREQ=$(echo "$RXFREQ - $RXBANDWIDTH/2 - 1000" | bc)
# Calculate the frequency estimator limits
FSK_LOWER=1000
FSK_UPPER=$(echo "$FSK_LOWER + $RXBANDWIDTH" | bc)
echo "Using SDR Centre Frequency: $SDR_RX_FREQ Hz."
echo "Using FSK estimation range: $FSK_LOWER - $FSK_UPPER Hz"
BIAS_SETTING=""
if [ "$BIAS" = "1" ]; then
echo "Enabling Bias Tee."
BIAS_SETTING=" -T"
fi
GAIN_SETTING=""
if [ "$GAIN" = "0" ]; then
echo "Using AGC."
GAIN_SETTING=""
else
echo "Using Manual Gain"
GAIN_SETTING=" -g $GAIN"
fi
# Start the receive chain.
# Note that we now pass in the SDR centre frequency ($SDR_RX_FREQ) and 'target' signal frequency ($RXFREQ)
# to enable providing additional metadata to Habitat / Sondehub.
rtl_fm -M raw -F9 -s 48000 -p $PPM $GAIN_SETTING$BIAS_SETTING -f $SDR_RX_FREQ | $DECODER -q --stats=5 -g -m binary --fsk_lower=$FSK_LOWER --fsk_upper=$FSK_UPPER - - | python -m horusdemodlib.uploader --freq_hz $SDR_RX_FREQ --freq_target_hz $RXFREQ $@