boards/weact-f411ce: enable automatic reset to bootloader

boards/weact-f411ce/Makefile.dep

@@ -6,6 +6,12 @@ ifeq (,$(filter stdio_% slipdev_stdio,$(USEMODULE)))
   USEMODULE += stdio_cdc_acm
 endif
 
+ifneq (,$(filter stdio_cdc_acm,$(USEMODULE)))
+  # The Mask-ROM bootloader provides USB-DFU capability
+  FEATURES_REQUIRED += bootloader_stm32
+  USEMODULE += usb_board_reset
+endif
+
 ifneq (,$(filter mtd,$(USEMODULE)))
   USEMODULE += mtd_spi_nor
 endif

boards/weact-f411ce/Makefile.include

@@ -6,5 +6,9 @@ DFU_USB_ID ?= 0483:df11
 DFU_FLAGS  ?= -a 0 -s 0x08000000:leave
 ROM_OFFSET ?= 0x0
 
+# CDC ACM is available faster on STM32
+TERM_DELAY ?= 1
+
 # Setup of programmer and serial is shared between STM32 based boards
 include $(RIOTMAKE)/boards/stm32.inc.mk
+include $(RIOTMAKE)/tools/usb_board_reset.mk

boards/weact-f411ce/doc.txt

@@ -36,21 +36,25 @@ It is available on sites like AliExpress for less than 4€.
 ## Flashing the device
 The device comes with a bootloader that allows flashing via `dfu-util`.
 
-There are two buttons on the board labeled `BOOT0` and `NRST`.
-
- - Press and hold down `NRST` to reset the CPU
- - Press `BOOT0` while keeping `NRST` held down
- - Release `NRST`, afterwards release `BOOT0`
-
-The board will now show up as `0483:df11` - `STM32 BOOTLOADER` and will accept
-firmware using the DFU protocol.
-
-You can upload your RIOT-firmware by typing
+If RIOT is already running on the board, you can upload your RIOT-firmware by typing
 
 ```
 make BOARD=weact-f411ce flash
 ```
 
+RIOT will make sure to enter the bootloader automatically.
+
+If RIOT crashed or you have the plain board with the stock firmware, you have to enter
+the bootloader manually.
+
+There are two buttons on the board labeled `BOOT0` and `NRST`.
+
+ - Hold down `BOOT0`
+ - Shortly press `NRST` to reset the CPU while keeping `BOOT0` held down
+
+The board will now show up as `0483:df11` - `STM32 BOOTLOADER` and will accept
+firmware using the DFU protocol.
+
 *Note:* You need to have write permissions to the device.
 On Linux you could add yourself to the `plugdev` group and store the following as `/etc/udev/rules.d/99-weact-f411ce.rules`: