diff --git a/upload.sh b/upload.sh
index 7607d67..0c86404 100755
--- a/upload.sh
+++ b/upload.sh
@@ -1,11 +1,9 @@
 #!/bin/bash
 
-#serial=`ls /dev/ | grep cu.usbserial`
-#echo ${serial}
-
+# 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}'`
 
 echo ${serial}
 
+# upload sketch in this folder
 arduino-cli upload --fqbn esp32:esp32:m5stick-c -p ${serial} "."
-#arduino-cli upload --fqbn esp32:esp32:m5stick-c -p /dev/${serial} "."