Allow boot messages on SWO instead of serial port.

Author: Seppo Takalo

mbed_lib.json

@@ -32,6 +32,11 @@
             "value": 1,
             "macro_name": "SHOW_SERIAL_OUTPUT"
         },
+        "show-swo-output": {
+            "help": "Show boot status and progress on SWO output instead of serial.",
+            "value": 0,
+            "macro_name": "SHOW_SWO_OUTPUT"
+        },
         "use-kvstore-rot": {
             "help": "use nvstore implementation of the ROT to authenticate firmware headers",
             "value": 1,

source/bootloader_common.c renamed to source/bootloader_common.cpp

@@ -17,6 +17,9 @@
 // ----------------------------------------------------------------------------
 
 #include "bootloader_common.h"
+#include "mbed.h"
+#include "hal/serial_api.h"
+#include "SerialWireOutput.h"
 
 /* buffer used in storage operations */
 uint8_t buffer_array[BUFFER_SIZE];
@@ -29,9 +32,7 @@ const char hexTable[16] = {'0', '1', '2', '3', '4', '5', '6', '7',
 
 #if DEVICE_SERIAL && SHOW_SERIAL_OUTPUT
 
-#include "hal/serial_api.h"
-
-static serial_t uart = { 0 };
+static serial_t uart = {};
 
 /* module variable for keeping track of initialization */
 static bool not_initialized = true;
@@ -68,6 +69,14 @@ void boot_debug(const char *s)
     }
 }
 
+#elif DEVICE_ITM && SHOW_SWO_OUTPUT
+
+void boot_debug(const char *s)
+{
+    static SerialWireOutput swo;
+    swo.write(s, strlen(s));
+}
+
 #else
 
 /**