Allow decoding of negative frequencies, add triple rx script

src/horus_demod.c

@@ -53,7 +53,7 @@ int main(int argc, char *argv[]) {
     float    loop_time;
     int      enable_stats = 0;
     int      quadrature = 0;
-    int fsk_lower = -1;
+    int fsk_lower = -99999;
     int fsk_upper = -1;
     int Rs = -1;
     int tone_spacing = -1;
@@ -224,9 +224,11 @@ int main(int argc, char *argv[]) {
         stats_ctr = 0;
     }
 
-    if((fsk_lower> 0) && (fsk_upper > fsk_lower)){
+    if((fsk_upper > fsk_lower) && (fsk_lower > -99999)){
         horus_set_freq_est_limits(hstates, fsk_lower, fsk_upper);
         fprintf(stderr,"Setting estimator limits to %d to %d Hz.\n",fsk_lower, fsk_upper);
+    } else {
+        printf(stderr,"Not setting estimator limits, upper must be higher than lower.");
     }
 
     

start_triple_4fsk.sh

@@ -0,0 +1,136 @@
+#!/usr/bin/env bash
+#
+#	Horus Binary *Triple* Decoder Script
+#	Intended for situations with three payloads in the air, spaced ~10 kHz apart.
+#   NOTE - Ensure your horus_demod build is from newer than ~5th April 2024, else this
+#   will not work correctly!
+#
+#   It also possible to extend this approach further to handle as many transmissions
+#   as can be safely fitted into the receiver passband (+/- 24 kHz). Spacings of
+#   5 kHz between transmissions is possible with frequency stable transmitters (e.g. RS41s)
+#   Don't try this with DFM17's, which drift a lot!
+#
+
+# Change directory to the horusdemodlib directory.
+# If running as a different user, you will need to change this line
+cd /home/pi/horusdemodlib/
+
+# The following settings are an example for a situation where there are three transmitters in the air,
+# on: 434.190 MHz, 434.200 MHz, and 434.210 MHz.
+
+# The *centre* frequency of the SDR Receiver, in Hz.
+# It's recommended that this not be tuned directly on top of one of the signals we want to receive,
+# as sometimes we can get a DC spike which can affect the demodulators.
+# In this example the receiver has been tuned in the middle of 2 of the signals, at 434.195 MHz.
+RXFREQ=434195000
+
+# Where to find the first signal - in this case at 434.190 MHz, so -5000 Hz below the centre.
+MFSK1_SIGNAL=-5000
+
+# Where to find the second signal - in this case at 434.200 MHz, so 5000 Hz above the centre.
+MFSK2_SIGNAL=5000
+
+# Where to find the third signal - in this case at 434.210 MHz, so 15000 Hz above the centre.
+MFSK3_SIGNAL=15000
+
+# 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.
+RXBANDWIDTH=8000
+
+# RTLSDR Device Selection
+# If you want to use a specific RTLSDR, you can change this setting to match the 
+# device identifier of your SDR (use rtl_test to get a list)
+SDR_DEVICE=0
+
+# 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)
+# NOTE: This uses the -T bias-tee option which is only available on recent versions
+# of rtl-sdr. Check if your version has this option by running rtl_fm --help and looking
+# for it in the option list.
+# If not, you may need to uninstall that version, and then compile from source: https://github.com/osmocom/rtl-sdr
+BIAS=0
+
+# Receiver PPM offset
+PPM=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 $VENV_DIR/bin/activate
+fi
+
+
+# Calculate the frequency estimator limits for each decoder
+MFSK1_LOWER=$(echo "$MFSK1_SIGNAL - $RXBANDWIDTH/2" | bc)
+MFSK1_UPPER=$(echo "$MFSK1_SIGNAL + $RXBANDWIDTH/2" | bc)
+MFSK1_CENTRE=$(echo "$RXFREQ + $MFSK1_SIGNAL" | bc)
+
+MFSK2_LOWER=$(echo "$MFSK2_SIGNAL - $RXBANDWIDTH/2" | bc)
+MFSK2_UPPER=$(echo "$MFSK2_SIGNAL + $RXBANDWIDTH/2" | bc)
+MFSK2_CENTRE=$(echo "$RXFREQ + $MFSK2_SIGNAL" | bc)
+
+MFSK3_LOWER=$(echo "$MFSK3_SIGNAL - $RXBANDWIDTH/2" | bc)
+MFSK3_UPPER=$(echo "$MFSK3_SIGNAL + $RXBANDWIDTH/2" | bc)
+MFSK3_CENTRE=$(echo "$RXFREQ + $MFSK3_SIGNAL" | bc)
+
+echo "Using SDR Centre Frequency: $RXFREQ Hz."
+echo "Using MFSK1 estimation range: $MFSK1_LOWER - $MFSK1_UPPER Hz"
+echo "Using MFSK2 estimation range: $MFSK2_LOWER - $MFSK2_UPPER Hz"
+echo "Using MFSK3 estimation range: $MFSK3_LOWER - $MFSK3_UPPER Hz"
+
+BIAS_SETTING=""
+
+if [ "$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 $GAIN"
+fi
+
+STATS_SETTING=""
+
+if [ "$STATS_OUTPUT" = "1" ]; then
+	echo "Enabling Modem Statistics."
+	STATS_SETTING=" --stats=100"
+fi
+
+# Start the receive chain.
+# Note that we now pass in the SDR centre frequency ($RXFREQ) and 'target' signal frequency ($MFSK1_CENTRE)
+# to enable providing additional metadata to SondeHub
+rtl_fm -M raw -F9 -d $SDR_DEVICE -s 48000 -p $PPM $GAIN_SETTING$BIAS_SETTING -f $RXFREQ \
+  | tee >($DECODER -q --stats=5 -g -m binary --fsk_lower=$MFSK1_LOWER --fsk_upper=$MFSK1_UPPER - - | python -m horusdemodlib.uploader --freq_hz $RXFREQ --freq_target_hz $MFSK1_CENTRE ) \
+  | tee >($DECODER -q --stats=5 -g -m binary --fsk_lower=$MFSK3_LOWER --fsk_upper=$MFSK3_UPPER - - | python -m horusdemodlib.uploader --freq_hz $RXFREQ --freq_target_hz $MFSK3_CENTRE ) \
+  >($DECODER -q --stats=5 -g -m binary --fsk_lower=$MFSK2_LOWER --fsk_upper=$MFSK2_UPPER - - | python -m horusdemodlib.uploader --freq_hz $RXFREQ ) > /dev/null