Add semihosting support for nrf52 devices (#4137)

* Turn off vscode cmake prompt - we don't use cmake on meshtastic

* Add rak4631_dap variant for debugging with NanoDAP debug probe device.

* The rak device can also run freertos (which is underneath nrf52 arduino)

* Add semihosting support for nrf52840 devices
Initial platformio.ini file only supports rak4630
Default to non TCP for the semihosting log output for now...
Fixes https://github.com/meshtastic/firmware/issues/4135

* fix my botched merge - keep board_level = extra flag for rak3631_dbg

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

variants/rak4631/platformio.ini

@@ -20,6 +20,7 @@ lib_deps =
 debug_tool = jlink
 
 
+
 ; If not set we will default to uploading over serial (first it forces bootloader entry by talking 1200bps to cdcacm)
 ; Note: as of 6/2013 the serial/bootloader based programming takes approximately 30 seconds
 ;upload_protocol = jlink
@@ -27,26 +28,92 @@ debug_tool = jlink
 ; Allows programming and debug via the RAK NanoDAP as the default debugger tool for the RAK4631 (it is only $10!)
 ; programming time is about the same as the bootloader version.
 ; For information on this see the meshtastic developers documentation for "Development on the NRF52"
-[env:rak4631_dap]
+[env:rak4631_dbg]
 extends = env:rak4631
 board_level = extra
-; pyocd pack --i nrf52840
+
+; if the builtin version of openocd has a buggy version of semihosting, so use the external version
+; platform_packages = platformio/tool-openocd@^3.1200.0
+
+build_flags =
+  ${env:rak4631.build_flags}
+  -D USE_SEMIHOSTING
+
+lib_deps =
+  ${env:rak4631.lib_deps}
+  https://github.com/geeksville/Armduino-Semihosting.git#35b538fdf208c3530c1434cd099a08e486672ee4
+
+; NOTE: the pyocd support for semihosting is buggy.  So I switched to using the builtin platformio support for the stlink adapter which worked much better.
+; However the built in openocd version in platformio has buggy support for TCP to semihosting. 
+;
+; So I'm now trying the external openocd - but the openocd scripts for nrf52.cfg assume you are using a DAP adapter not an STLINK adapter.
+; In theory I could change those scripts.  But for now I'm trying going back to a DAP adapter but with the external openocd.
+
+upload_protocol = stlink
 ; eventually use platformio/tool-pyocd@^2.3600.0 instad
-upload_protocol = custom
-upload_command = pyocd flash -t nrf52840 $UPLOADERFLAGS $SOURCE
+;upload_protocol = custom
+;upload_command = pyocd flash -t nrf52840 $UPLOADERFLAGS $SOURCE
+
+; We want the initial breakpoint at setup() instead of main().  Also we want to enable semihosting at that point so instead of
+; debug_init_break = tbreak setup
+; we just turn off the platformio tbreak and do it in .gdbinit (where we have more flexibility for scripting)
+; also we use a permanent breakpoint so it gets reused each time we restart the debugging session?
+debug_init_break = tbreak setup
+
+; Note: add "monitor arm semihosting_redirect tcp 4444 all" if you want the stdout from the device to go to that port number instead
+; (for use by meshtastic command line)
+;  monitor arm semihosting disable
+;  monitor debug_level 3
+;
+; IMPORTANT: fileio must be disabled before using port 5555 - openocd ver 0.12 has a bug where if enabled it never properly parses the special :tt name
+; for stdio access.
+;   monitor arm semihosting_redirect tcp 5555 stdio
+
+; Also note: it is _impossible_ to do non blocking reads on the semihost console port (an oversight when ARM specified the semihost API).
+; So we'll neve be able to general purpose bi-directional communication with the device over semihosting.
+debug_extra_cmds =
+  echo Running .gdbinit script
+  monitor arm semihosting enable
+  monitor arm semihosting_fileio enable
+  monitor arm semihosting_redirect disable
+  commands 1
+  echo Breakpoint at setup() has semihosting console, connect to it with "telnet localhost 5555"
+  set wantSemihost = true
+  end
+
 
 ; Only reprogram the board if the code has changed
 debug_load_mode = modified
 ;debug_load_mode = manual
-debug_tool = custom
+debug_tool = stlink
+;debug_tool = custom
+; debug_server =
+;  openocd
+;  -f
+;  /usr/local/share/openocd/scripts/interface/stlink.cfg
+;  -f
+;  /usr/local/share/openocd/scripts/target/nrf52.cfg
+; $PLATFORMIO_CORE_DIR/packages/tool-openocd/openocd/scripts/interface/cmsis-dap.cfg
+
+; Allows programming and debug via the RAK NanoDAP as the default debugger tool for the RAK4631 (it is only $10!)
+; programming time is about the same as the bootloader version.
+; For information on this see the meshtastic developers documentation for "Development on the NRF52"
 ; We manually pass in the elf file so that pyocd can reverse engineer FreeRTOS data (running threads, etc...)
-debug_server =
-  pyocd
-  gdbserver
-  -t
-  nrf52840
-  --elf
-  ${platformio.build_dir}/${this.__env__}/firmware.elf
+;debug_server =
+;  pyocd
+;  gdbserver
+;  -j
+;  ${platformio.workspace_dir}/..
+;  -t
+;  nrf52840
+;  --semihosting
+;  --elf
+;  ${platformio.build_dir}/${this.__env__}/firmware.elf
+
+; If you want to debug the semihosting support you can turn on extra logging in pyocd with
+;   -L
+;   pyocd.debug.semihost.trace=debug
+
 ; The following is not needed because it automatically tries do this
 ;debug_server_ready_pattern = -.*GDB server started on port \d+.*
 ;debug_port = localhost:3333