diff --git a/upload.sh b/upload.sh
index 0c86404..51b70e8 100755
--- a/upload.sh
+++ b/upload.sh
@@ -1,9 +1,23 @@
 #!/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}'`
+## get serial port via board list, choose lines including "USB", and pick up 1st word
+serials=`arduino-cli board list | grep USB | awk '{print $1}'`
 
-echo ${serial}
+# echo ${serials}
+if [ -z "${serials}" ]; then
+  echo "No device connected."
+  exit  
+fi
 
-# upload sketch in this folder
-arduino-cli upload --fqbn esp32:esp32:m5stick-c -p ${serial} "."
+
+## if multiple ports found, try uploading to all ports.
+seriallist=($serials)
+
+## print the list
+# echo ${seriallist[@]}
+
+for ser in ${seriallist[@]} ; do
+    echo ${ser}
+    arduino-cli upload --fqbn esp32:esp32:m5stick-c -p ${ser} "."
+done
+