Early work on the et-wwv wrapper script

overlay/opt/emcomm-tools/bin/et-common

@@ -1,7 +1,7 @@
 #!/bin/bash
 # Author  : Gaston Gonzalez
 # Date    : 1 February 2025
-# Updated : 7 October 2025
+# Updated : 16 April 2026
 # Purpose : Common environment variables and functions
 
 # Standardized device paths for supported hardware
@@ -40,6 +40,13 @@ exit_if_no_sdr() {
   fi
 }
 
+exit_if_no_audio() {
+  if [[ ! -e ${ET_DEVICE_AUDIO} ]]; then
+    et-log "No ${ET_DEVICE_AUDIO} detected."
+    exit 1
+  fi
+}
+
 exit_on_service_failure() {
   local systemd_unit_name="$1"
   systemctl is-active --user --quiet "${systemd_unit_name}"