Use WIP pico_debug module to get debug information on CPU trap

Author: ole

CMakeLists.txt

@@ -74,8 +74,40 @@ add_executable(PicoLinksSwift
 )
 
 target_link_libraries(PicoLinksSwift
-    pico_stdlib
     $<TARGET_OBJECTS:myswiftlib>
+    pico_stdlib
+
+    # Prints debugging information (register values and stack contents)
+    # to stdout when an exception occurs. Example output:
+    # 
+    # ```
+    # -----------------------------------------------------------
+    # Unhandled Hard Fault exception on core 0
+    # -----------------------------------------------------------
+    #   R0: 000000c8   R1: 0000012c   R2: 00001000   R3: e0900001
+    #   R4: 1000026c   R5: d0000000   R6: 02000000   R7: 00000000
+    #   R8: ffffffff   R9: ffffffff  R10: ffffffff  R11: ffffffff
+    #  R12: 40014000   SP: 20041fe8   LR: 10000339   PC: e0900000
+    #                 MSP: 20041fe8  PSP: fffffffc XPSR: 01000000
+    #          EXC_RETURN: fffffff9             PRIMASK: 00000000
+    # -----------------------------------------------------------
+    # 20041fe8: 00000001 1000026c 20041f01 18000000
+    # 20041ff8: 00000000 1000022b                  
+    # 20042008:                                    
+    # 20042018:                                    
+    # 20042028:                                    
+    # 20042038:                                    
+    # 20042048:                                    
+    # 20042058:    
+    # ```
+    #
+    # The pico_debug module is introduced in a pull request from 2022-09:
+    # Print registers, stack & other details on unhandled exception
+    # <https://github.com/raspberrypi/pico-sdk/pull/1026>, which hasn't been
+    # merged as of 2023-12-13.
+    #
+    # You need to check out this branch in your PICO_SDK_PATH folder to use it.
+    pico_debug
 )
 
 # create map/bin/hex file etc.