Echo test isr

Revision:
0:3aa4ba0ada56
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed_app.json	Fri Oct 23 13:51:26 2020 +0000
@@ -0,0 +1,7 @@
+{
+    "requires": ["bare-metal"],
+    "target_overrides": {
+      "*": {     
+      }
+    }
+}
\ No newline at end of file