diff --git a/src/TestBuild/monitor.sh b/src/TestBuild/monitor.sh
index b541b2a..b4e05f0 100755
--- a/src/TestBuild/monitor.sh
+++ b/src/TestBuild/monitor.sh
@@ -4,6 +4,10 @@
 serial=`arduino-cli board list | grep USB | awk '{print $1}'`
 
 echo ${serial}
+if [ -z "${serial}" ]; then
+  echo "No device connected."
+  exit  
+fi
 
 # open serial monitor (CTRL+C to quit)
 arduino-cli monitor -p ${serial} --config baudrate=115200 
diff --git a/src/TestBuild/upload.sh b/src/TestBuild/upload.sh
index 0c86404..c311436 100755
--- a/src/TestBuild/upload.sh
+++ b/src/TestBuild/upload.sh
@@ -1,9 +1,13 @@
 #!/bin/bash
 
 # get serial port via board list, choose lines including "USB", and pick up 1st word
-serial=`arduino-cli board list | grep USB | awk '{print $1}'`
+serial=`arduino-cli board list | grep USB | awk '{print $1}'` 
 
 echo ${serial}
+if [ -z "${serial}" ]; then
+  echo "No device connected."
+  exit  
+fi
 
 # upload sketch in this folder
 arduino-cli upload --fqbn esp32:esp32:m5stick-c -p ${serial} "."