mbed_app.json configured to operate on senet

To enable cayenne, edit mbed_app.json, assign pins for desired function

Example:

        "cayenne": {
            "help": "compile main_cayenne.cpp instead of main.cpp",
            "value": 1
        },
        "analog_in_pin": {
            "help": "PA_0, PA_4, PA_5",
            "value": "PA_0"
        },
        "analog_out_pin": {
            "help": "PA_0, PB_5, PB_10, PB_11",
            "value": "PB_11"
        },
        "_digital_out_pin": {
            "help": "",
            "value": ""
        }
Revision:
8:7594ad70d2bf
Parent:
0:7037ed05f54f
Child:
17:2fc16c1d6434
--- a/trace_helper.cpp	Fri Mar 16 07:00:18 2018 +0000
+++ b/trace_helper.cpp	Mon Mar 19 14:15:18 2018 +0000
@@ -77,7 +77,7 @@
      */
     static void trace_printer(const char* str)
     {
-        printf("%s\r\n", str);
+        pc.printf("%s\r\n", str);
     }
 
 #else