boards/stm32f411-minimum: Add README.txt

2023-04-03 05:45:30 +03:00 · 2023-04-03 05:45:30 +03:00 · f09f167592
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+README
+======
+
+This README discusses issues unique to NuttX configurations for the
+WeAct Studio MiniF4 minimum system development board.
+
+Contents
+========
+
+  - Board information
+  - LEDs
+  - UARTs
+  - USB
+  - SPI NOR Flash
+  - Configurations
+
+Board information
+=================
+
+It is sometimes referred to as "black pill", although there are several clone
+boards with f103-like chips and even an official f103 blackpill from Robotdyn.
+Both WeAct Studio (via Taobao and Aliexpress) and Adafruit sell the boards as
+"BlackPill Core Board" with STM32F411CEU6 or STM32F401CCU6 or
+"STM32F411 BlackPill Development board", so we'll assume that
+WeAct Studio is the original manufacturer and F401/F411 is the chip.
+
+Board documentation:
+https://github.com/WeActStudio/WeActStudio.MiniSTM32F4x1
+
+Summary pages from STM32-base
+https://stm32-base.org/boards/STM32F401CCU6-WeAct-Black-Pill-V1.2.html
 https://stm32-base.org/boards/STM32F411CEU6-WeAct-Black-Pill-V2.0.html
+https://stm32-base.org/boards/STM32F401CEU6-WeAct-Black-Pill-V3.0.html
+
+The board features:
+
+  - On-board 64 Mbits (8 MBytes) External SPI-NOR Flash (optional),
+  - nRST reset button and BOOT0 ST BootROM entry button,
+  - One user LED and one user push-button,
+  - HSE 25 Mhz and LSE 32.768 kHz,
+  - USB OTG FS with micro-AB connector,
+  - Around 30 remappable GPIOs on 2.54mm headers (after excluding 7 power pins,
+    two LSE pins, the LED pin, NRST, BOOT1 and the SWD header),
+  - Serial Wire Debug header for use with an external SWD/JTAG adapter.
+
+As F4 series have a USB DFuSe-capable BootROM [AN2606], the board can be flashed
+via `dfu-util` over USB, or via `stm32flash` over UART without any debuggers.
+
+LEDs
+====
+
+  The STM32F411 Minimum board has only one software controllable LED on PC13.
+  This LED can be used by the board port when CONFIG_ARCH_LEDS option is
+  enabled.
+
+  If enabled the LED is simply turned on when the board boots
+  successfully, and is blinking on panic / assertion failed.
+
+UARTs
+=====
+
+  UART/USART PINS
+  ---------------
+
+  USART1
+    TX      PA9
+    RX      PA10
+  USART2
+    CTS     PA0
+    RTS     PA1
+    TX      PA2
+    RX      PA3
+    CK      PA4
+
+Default USART/UART Configuration
+--------------------------------
+
+  USART1 (RX & TX only) is available through pins PA9 (TX) and PA10 (RX).
+
+USB
+===
+
+The board routes F401/F411's built-in FS PHY to a USB-C (non-dual-role) port.
+The chips still have a DWC2 USBOTG IP core, but only device mode is used.
+Note that only V3.1 PCB got a DNI solder bridge to short 5V and USB VBUS.
+Previous revisions had no support for USB host because of lack of port power
+as well as 5k pull-downs on USB-C CC1/CC2 pins (not affecting USB-A adapters).
+Because of this we are not considering USBOTG-FS Host configurations and
+do not map OTG_VBUS, OTG_ID pins to FS PHY, also no OVER/PWRON GPIOs.
+
+SPI NOR Flash
+=============
+
+The seller may send boards with soldered on-board SPI NOR Flash, usually
+Winbond W25Q64JVSIQ (QuadSPI) or similar. F401/F411 lack QuadSPI support.
+NuttX supports such MTD storage via special drivers and filesystems.
+For example, external flash can be formatted with SmartFS (or NXFFS, LittleFS)
+and mounted on boot by board init code or interactively from NSH.
+
+Configurations
+==============
+
+Each stm32f411-minimum configuration is maintained in a sub-directory and
+can be selected as follow:
+
+    tools/configure.sh stm32f411-minimum:<subdir>
+
+  Where <subdir> is one of the following:
+
+
+  Configuration Directories
+  -------------------------
+
+  nsh:
+  ---
+    Configures the NuttShell (nsh) located at apps/examples/nsh. This
+    configuration enables a serial console on UART1.