Documentation/platforms/arm/stm32h7/boards: Add page for nucleo-h723zg

Add page for the nucleo-h723zg board into the documentation.

Signed-off-by: Michal Matias <mich4l.matias@gmail.com>

Author: matiamic

Documentation/platforms/arm/stm32h7/boards/nucleo-h723zg/index.rst

@@ -0,0 +1,112 @@
+================
+ST Nucleo H723ZG
+================
+
+.. tags:: chip:stm32, chip:stm32h7, chip:stm32h723
+
+This page discusses issues unique to NuttX configurations for the
+STMicro Nucleo-H723ZG development board featuring the STM32H723ZG
+MCU. The STM32H723ZG is a up-to 550MHz Cortex-M7 operation with 1MByte Flash
+memory and 564KBytes of SRAM. The board features:
+
+- On-board ST-LINK/V2-1 for programming and debugging,
+- 3 user LEDs
+- Two pushbuttons (user and reset)
+- 32.768 kHz crystal oscillator
+- USB OTG HS with Micro-AB connector
+- Ethernet connector compliant with IEEE-802.3-2002
+- Board connectors:
+  - USB with Micro-AB
+  - SWD
+  - Ethernet RJ45
+  - ST Zio connector including Arduino Uno V3
+  - ST morpho
+
+Refer to the http://www.st.com website for further information about this
+board (search keyword: Nucleo-H723ZG)
+
+Serial Console
+==============
+
+Many options are available for a serial console via the Morpho connector.
+Here two common serial console options are suggested:
+
+1. Arduino Serial Shield.
+
+   If you are using a standard Arduino RS-232 shield with the serial
+   interface with RX on pin D0 and TX on pin D1 from USART6:
+
+      ======== ========= =====
+      ARDUINO  FUNCTION  GPIO
+      ======== ========= =====
+      DO RX    USART6_RX PG9
+      D1 TX    USART6_TX PG14
+      ======== ========= =====
+
+2. Nucleo Virtual Console.
+
+   The virtual console uses Serial Port 3 (USART3) with TX on PD8 and RX on
+   PD9.
+
+      ================= ===
+      VCOM Signal       Pin
+      ================= ===
+      SERIAL_RX         PD9
+      SERIAL_TX         PD8
+      ================= ===
+
+   These signals are internally connected to the on board ST-Link.
+
+   The Nucleo virtual console is the default serial console in all
+   configurations unless otherwise stated in the description of the
+   configuration.
+
+Configurations
+==============
+
+Information Common to All Configurations
+----------------------------------------
+
+Each Nucleo-H723ZG configuration is maintained in a sub-directory and
+can be selected as follow::
+
+    tools/configure.sh [options] nucleo-h723zg:<subdir>
+
+Where options should specify the host build platform (-l for Linux, -c for
+Cygwin under Windows, etc.).  Try ``tools/configure.sh -h`` for the complete
+list of options.
+
+Before starting the build, make sure that (1) your PATH environment variable
+includes the correct path to your toolchain, and (2) you have the correct
+toolchain selected in the configuration.
+
+And then build NuttX by simply typing the following.  At the conclusion of
+the make, the nuttx binary will reside in an ELF file called, simply, nuttx.::
+
+    make
+
+Configuration Sub-directories
+=============================
+
+nsh:
+----
+
+This configuration provides a basic NuttShell configuration (NSH)
+for the Nucleo-H723ZG.  The default console is the VCOM on USART3.
+
+netnsh:
+--------
+
+This configuration enables support for the Ethernet and a set
+of networking functionalities.
+
+.. NOTE::
+    The initialization logic waits for Ethernet auto negotiation to complete
+    up to a timeout. The timeout is a number of times the MII status register
+    is read from the PHY. First to verify the link status is up, subsequently
+    to verify the auto negotiation is complete. The timeout is set to a fixed
+    value of ``PHY_RETRY_TIMEOUT=0x1998``.
+    In each cycle the program waits for ``nxsched_usleep(100)``. By default
+    this gets rounded up to the value of the tick time which is 10 ms!
+    Therefore the time you will wait for the nsh console if the Ethernet
+    is not plugged in is ``2 * 10 ms * 0x1998 = 130s``.