doc: Introduct debugging and downloading using Jlink on stm32 boards

Introduct the ways to debugging and downloading using JLink tools on
stm32 boards if had convented ST-Link On-Board into a JLink.

Signed-off-by: qianfan Zhao <qianfanguijin@163.com>

doc/tools/stlink-v21.rst

@@ -0,0 +1,126 @@
+:orphan:
+
+.. _stlink-v21:
+
+ST-LINK/V2-1
+############
+
+Overview
+********
+
+ST-LINK/V2-1 is a serial and debug adapter built into all Nucleo and Discovery
+boards. It provides a bridge between your computer (or other USB host) and the
+embedded target processor, which can be used for debugging, flash programming,
+and serial communication, all over a simple USB cable.
+
+SEGGER offers a firmware upgrading the ST-LINK/V2-1 on board on the Nucleo and
+Discovery boards. This firmware makes the ST-LINK/V2-1 compatible with J-Link
+OB, allowing users to take advantage of most J-Link features like the ultra fast
+flash download and debugging speed or the free-to-use GDBServer.
+
+More informations about upgrading ST-LINK/V2-1 to JLink or restore ST-Link/V2-1
+firmware please visit: `SEGGER`_
+
+Zephyr supports the following debug tools through ST-LINK/V2-1:
+
+* :ref:`st_ST-LINK/V2-1_stlink`
+* :ref:`st_ST-LINK/V2-1_jlink`
+
+.. _st_ST-LINK/V2-1_stlink:
+
+ST-LINK/V2-1
+************
+
+ST-Link tool is available by default, flash and debug could be done as follows.
+
+Flashing
+========
+
+  .. zephyr-app-commands::
+     :zephyr-app: samples/hello_world
+     :goals: flash
+
+Debugging
+=========
+
+  .. zephyr-app-commands::
+     :zephyr-app: samples/hello_world
+     :goals: debug
+
+
+.. _st_ST-LINK/V2-1_jlink:
+
+Segger J-Link
+*************
+
+Host Tools and Firmware
+=======================
+
+Download and install the `Segger J-Link Software and Documentation Pack`_ to
+get the J-Link GDB server for your host computer.
+
+Flashing
+========
+
+Use the CMake ``flash`` target with the argument ``STLINK_FW=jlink`` to
+build your Zephyr application.
+
+  .. zephyr-app-commands::
+     :zephyr-app: samples/hello_world
+     :gen-args: -DSTLINK_FW=jlink
+     :goals: flash
+
+Debugging
+=========
+
+Use the CMake ``debug`` target with the argument ``STLINK_FW=jlink`` to build
+your Zephyr application, invoke the J-Link GDB server, attach a GDB client, and
+program your Zephyr application to flash. It will leave you at a GDB prompt.
+
+  .. zephyr-app-commands::
+     :zephyr-app: samples/hello_world
+     :gen-args: -DSTLINK_FW=jlink
+     :goals: debug
+
+Console
+=======
+
+If you configured your Zephyr application to use a UART console (most boards
+enable this by default), open a serial terminal (minicom, putty, etc.) with the
+following settings:
+
+- Speed: 115200
+- Data: 8 bits
+- Parity: None
+- Stop bits: 1
+
+If you configured your Zephyr application to use `Segger RTT`_ console instead,
+open telnet:
+
+  .. code-block:: console
+
+     $ telnet localhost 19021
+     Trying ::1...
+     Trying 127.0.0.1...
+     Connected to localhost.
+     Escape character is '^]'.
+     SEGGER J-Link V6.30f - Real time terminal output
+     J-Link STLink V21 compiled Jun 26 2017 10:35:16 V1.0, SN=773895351
+     Process: JLinkGDBServerCLExe
+     Zephyr Shell, Zephyr version: 1.12.99
+     Type 'help' for a list of available commands
+     shell>
+
+If you get no RTT output you might need to disable other consoles which conflict
+with the RTT one if they are enabled by default in the particular sample or
+application you are running, such as disable UART_CONSOLE in menuconfig.
+
+
+.. _SEGGER:
+   https://www.segger.com/products/debug-probes/j-link/models/other-j-links/st-link-on-board/
+
+.. _Segger J-Link Software and Documentation Pack:
+   https://www.segger.com/downloads/jlink
+
+.. _Segger RTT:
+    https://www.segger.com/jlink-rtt.html