Add initial support for tinyuf2 bootloader (when hosted on F411 blackpill) (#12600)

* Add support for jumping to tinyuf2 bootloader. Adds blackpill UF2 example.

* Update flashing.md

* Update chconf.h

* Update config.h

* Update halconf.h

* Update mcuconf.h

keyboards/handwired/onekey/blackpill_f411_tinyuf2/chconf.h

@@ -0,0 +1,21 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#define CH_CFG_ST_FREQUENCY 10000
+
+#include_next <chconf.h>

keyboards/handwired/onekey/blackpill_f411_tinyuf2/config.h

@@ -0,0 +1,31 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "config_common.h"
+
+#define MATRIX_COL_PINS { B0 }
+#define MATRIX_ROW_PINS { A7 }
+#define UNUSED_PINS
+
+#define BACKLIGHT_PIN           A0
+#define BACKLIGHT_PWM_DRIVER    PWMD5
+#define BACKLIGHT_PWM_CHANNEL   1
+
+#define RGB_DI_PIN A1
+
+#define ADC_PIN A0

keyboards/handwired/onekey/blackpill_f411_tinyuf2/halconf.h

@@ -0,0 +1,22 @@
+/* Copyright 2021 QMK
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#define HAL_USE_I2C TRUE
+#define HAL_USE_PWM TRUE
+
+#include_next <halconf.h>

keyboards/handwired/onekey/blackpill_f411_tinyuf2/mcuconf.h

@@ -0,0 +1,24 @@
+/* Copyright 2021 QMK
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include_next "mcuconf.h"
+
+#undef STM32_I2C_USE_I2C1
+#define STM32_I2C_USE_I2C1 TRUE
+
+#undef STM32_PWM_USE_TIM5
+#define STM32_PWM_USE_TIM5 TRUE

keyboards/handwired/onekey/blackpill_f411_tinyuf2/readme.md

@@ -0,0 +1,9 @@
+# f411 blackpill onekey
+
+Supported Hardware: *STM32F411CEU6 WeAct v1.3*.
+
+To trigger keypress, short together pins *B0* and *A7*.
+
+This variant requires the TinyUF2 bootloader to be installed. This can be downloaded from the [tinyuf2 releases page](https://github.com/adafruit/tinyuf2/releases). The F401 blackpill binary works for both F401- and F411-based blackpill devices.
+
+Double-tap reset to enter bootloader mode. Copy the built uf2 file to the device by dragging the file to the new USB disk.

keyboards/handwired/onekey/blackpill_f411_tinyuf2/rules.mk

@@ -0,0 +1,10 @@
+# MCU name
+MCU = STM32F411
+
+# Build Options
+#   change yes to no to disable
+#
+KEYBOARD_SHARED_EP       = yes
+
+# We want to use the tinyuf2 bootloader...
+BOOTLOADER = tinyuf2