emcomm-tools-os-community/overlay/opt/emcomm-tools/bin/et-modem73

#!/bin/bash
#
# Author  : Gaston Gonzalez
# Date    : 30 June 2026
# Purpose : Wrapper script for starting modem73 with PnP support
#
# Preconditions:
# 1. Supported radio and audio interface are connected and properly detected
#
# Postconditions:
# 1. modem73 started with sane defaults
#
# Notes:
#
# modem73 supports many modulation types and configuration options. To
# keep usage simple, only five modulation settings have been configured
# that map to a combination of reliability and speed for most general
# purpose applications.
#
# In all cases, normal frames and 1/2 coding rate is used.
#
# There are faster speeds, but EmComm Tools has the design goal of 
# getting the message through and favoring delivery over speed..

MODEM73_CONF_FILE="${HOME}/.config/modem73/settings"

usage() {
  echo "usage: $(basename $0) <mode> [options]"
  echo "  <mode>"
  echo "    reliability - Max reliability (Slower Speed) [BPSK]"
  echo "    balanced    - Balanced (Reliability and Speed) [QPSK] RECOMMENDED"
  echo "    fast        - Fast (Low Reliability) [8PSK]"
  echo "    faster      - Faster (Lower Reliability) [QAM16]"
  echo "    fastest     - Fastest (Lowest Reliability) [QAM64]"
  echo ""
  echo "  [options]"
  echo "    --headless  - Run modem73 headless"
}

HEADLESS=""
MODE=""
MODE_ARGS=""
CALLSIGN="N0CALL"

for arg in "$@"; do
  case "$arg" in
    --headless)
      HEADLESS="--headless"
    ;;
    reliability|balanced|fast|faster|fastest)
      if [[ -n "${MODE}" ]]; then
        et-log "Only one mode may be specified."
        usage
        exit 1
      fi
      MODE="$arg"
    ;;
    *)
      echo "Unknown argument: $arg"
      usage
      exit 1
    ;;
  esac
done

if [[ -z "${MODE}" ]]; then
  et-log "Can't started modem73. Mode not specified."
  usage
  exit 1
fi

case "${MODE}" in
  reliability)
    MODE_ARGS="--modulation BPSK --normal --rate 1/2"
  ;;
  balanced)
    MODE_ARGS="--modulation QPSK --normal --rate 1/2"
  ;;
  fast)
    MODE_ARGS="--modulation 8PSK --normal --rate 1/2"
  ;;
  faster)
    MODE_ARGS="--modulation QAM16 --normal --rate 1/2"
  ;;
  fastest)
    MODE_ARGS="--modulation QAM64 --normal --rate 1/2"
  ;;
esac

[[ -z ${ET_LOG_DIR} ]] && ET_LOG_DIR="${HOME}/.local/share/emcomm-tools"
[[ ! -e ${ET_LOG_DIR} ]] && mkdir -p ${ET_LOG_DIR}

start() {
  update_config
  
  if [[ $? -eq 0 ]]; then

    systemctl is-active --quiet rigctld
    if [[ $? -ne 0 ]]; then
      et-log "Can't start modem73. rigctld not running. Ensure radio is selected."
      notify_user "Can't start modem73. rigctld not running."
      exit 1
    fi
  
    ALSA_DEVICE=$(et-system-info et-audio-card) 
    INPUT_AUDIO=$(modem73 --list-audio | grep input | grep $ALSA_DEVICE | cut -d":" -f3)
    OUTPUT_AUDIO=$(modem73 --list-audio | grep output| grep $ALSA_DEVICE | cut -d":" -f3)

    CMD="modem73 --input-device ${INPUT_AUDIO} --output-device ${OUTPUT_AUDIO} --ptt rigctl --callsign ${CALLSIGN} ${MODE_ARGS} ${HEADLESS}"
    et-log "Starting modem73 in mode ${MODE} with: '${CMD}'"
    echo
    ${CMD}
  else 
    et-log "Error configurating modem. Can't start modem73"
    exit 1
  fi
}

update_config () {

    # The modem73 configuration file causes issues when using it in combination with
    # command line arguments during manual runs. It is best to remove it before each
    # run and drive the modem using only command line arguments.
    if [[ -e "${MODEM73_CONF_FILE}" ]]; then
      et-log "Removing previous configuration file: ${MODEM73_CONF_FILE}"
      rm -v ${MODEM73_CONF_FILE}
    fi

    et-log "Attempting to start modem73 in mode: '${MODE}'"

    [[ -z "$ET_USER_CONFIG" ]] && ET_USER_CONFIG="${HOME}/.config/emcomm-tools/user.json"

    CALLSIGN=$(cat ${ET_USER_CONFIG} | jq -r .callsign)

    # 1. Check if the symlink was created by the udev rules
    if [[ -e /dev/et-audio ]]; then

       # 2. Check that this device was properly tagged with the ET_AUDIO env variable with a udev rule
       APLAY_OUT=$(arecord -l | grep ET_AUDIO)
       if [[ $? -eq 0 ]]; then

         # Configure ALSA settings for sound card
         /opt/emcomm-tools/bin/et-audio update-config

       else
         et-log "No ET_AUDIO device detected."
         notify_user "Can't start modem73. No ET_AUDIO device detected."
         exit 1
       fi
    else
      et-log "No ET_AUDIO device plugged in."
      notify_user "Can't start modem73. No supported audio device plugged in."
      exit 1
    fi

}

start