Schedule SDR recordings with a simple script.

sdr_schedule.sh

#!/bin/bash
set -e

# This is made for libmirisdr-5, but could be adapted easily to any IQ-spewing client.
# Depends on csdr (jketterl's fork) for decimation.

if [ -z "$1" ]; then
	echo "Usage: $0 (start date and time, e. g. 2024-02-10 00:10:15)"
	exit 1
fi

START_DATE="$(date -d "$1" +'%s')"
if [ $? -ne 0 ]; then
	echo "Invalid date format! Check usage..."
	exit 1
fi

# When to stop the recording
END_DATE="$(date -d '+150 minute' +'%s')"
FREQ=3650000
SAMPLE_RATE=6048000
DECIM=16
WAV_RATE=$((SAMPLE_RATE / DECIM)) # Should be an integer.





delayTime=$(( "$START_DATE" - "$(date +'%s')" ))
echo "==================== Will start in $delayTime seconds..."
if [[ "$delayTime" -gt 0 ]]; then
	sleep "$delayTime"
fi

isDone="no"
trap ctrl_c SIGINT
function ctrl_c() {
	echo "==================== Ctrl+C pressed! Exiting..." 
	isDone="yes"
}

cd "$(dirname "$0")"

PID_FILE="./miri.pid"
MIRI_PID=""

function start_miri {
	OUT_FILE="./baseband_${FREQ}_""$(date +'%Y-%m-%d_%H-%M-%S')"".raw"
	echo "==================== Starting recording to $OUT_FILE"

	# We need to trap again in a subshell.
	( trap '' INT ; miri_sdr -f $FREQ -s $SAMPLE_RATE -G 1,0,0,15 - & echo $! >"$PID_FILE" ) \
	| csdr convert -i s16 -o float \
	| csdr firdecimate $DECIM 0.08 -w hamming \
	| csdr convert -i float -o s16 \
	> "$OUT_FILE" &
	
	MIRI_PID="$(cat "$PID_FILE")"
	rm "$PID_FILE"
}

start_miri

while true; do
	if [[ "$(date +'%s')" -lt "$END_DATE" ]] && [[ "$isDone" == "no" ]]; then
		# We should be still recording. Check if the process has died.
		if ! kill -0 "$MIRI_PID" >/dev/null 2>&1; then
			# Process stopped, restart.
			start_miri
		fi
		
		sleep 1
	else
	    echo "==================== Recording finished."
	    # Wait for the process to end...
		while kill -0 "$MIRI_PID" >/dev/null 2>&1; do 
			kill "$MIRI_PID"
			sleep 1
		done

	    break
	fi
done


# split -b 4000M -d -a 1 'baseband_3650000_2024-02-10_05-45-00.raw' baseband_split_
# sox -t raw -e signed-integer -b 16 -c 2 -r $WAV_RATE - ./bb.wav