This is the blinky program with serial communication

Dependencies:   SEGGER_RTT

Revision:
0:78525a886bac
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed_app.json	Thu Oct 15 15:39:07 2020 +0000
@@ -0,0 +1,15 @@
+{
+    "target_overrides" : {
+        "NRF52840_DK" : {
+            "platform.stdio-baud-rate" : 9600 ,
+            "platform.default-serial-baud-rate" : 9600,
+            "platform.stdio-convert-newlines": true,
+            "target.features_add" : ["BLE"] ,
+            "target.extra_labels_add" : [ "CORDIO" , "CORDIO_LL" , "SOFTDEVICE_NONE", "NORDIC_CORDIO" ],
+            "target.extra_labels_remove" : [ "SOFTDEVICE_COMMON" , "SOFTDEVICE_S140_FULL5" , "NORDIC_SOFTDEVICE" ] ,
+            "target.lf_clock_src" : "NRF_LF_SRC_RC" ,
+            "target.lf_clock_rc_calib_timer_interval" : 16 ,
+            "target.lf_clock_rc_calib_mode_config" : 2
+        }
+    }
+}
\ No newline at end of file