Lolin S2 Mini - edited features & added flashing instructions

Author: durapensa

_board/lolin_s2_mini.md

@@ -13,16 +13,43 @@ features:
 
 ### Features
 
-- based ESP32-S2FN4R2 WIFI IC
-- Type-C USB
+- ESP32-S2FN4R2 WiFi SoC
+- USB Type-C connector, for built-in ROM USB bootloader & serial port debugging
 - 4MB Flash
 - 2MB PSRAM
 - 27x IO
 - ADC, DAC, I2C, SPI, UART, USB OTG
 - Compatible with LOLIN D1 mini shields
-- Compatible with MicroPython, Arduino and ESP-IDF
+- Compatible with CircuitPython, MicroPython, Arduino and ESP-IDF
 - Default firmware: MicroPython
 
+### Flashing UF2 Bootloader
+
+***Important***: *this will erase previously flashed firmware & sketches from the board.*
+
+- Download the latest `tinyuf2-lolin_s2_mini-......zip` from [TinyUF2 releases](https://github.com/adafruit/tinyuf2/releases),
+    - Unzip to find `combined.bin`.
+- Place board in bootloader mode:
+    - Plug board into a USB port on your computer using a data/sync cable. Make sure it is the only board plugged in, and that a charge-only cable is not being used.
+    - Press and hold the `0` button down. Don't let go of it yet!
+    - Press and release the `RST` button. You should have the `0` button pressed while you do this.
+    - Release the `0` button.
+- Use the Adafruit WebSerial ESPTool to upload `combined.bin` (Google Chrome 89 or newer):
+    - Open a new web browser window or tab to the [Adafruit WebSerial ESPTool](https://adafruit.github.io/Adafruit_WebSerial_ESPTool/)
+    - Select *460800 Baud* from the pull-down menu at the top-right of the page.
+    - Click the *Connect* button at the top-right of the page.
+    - Select the COM or Serial port from the pop-up window.
+    - After successful connection, click the `Erase` button.
+    - After successful erase, click the first `Choose a file...` button, locate the `combined.bin` file unzipped earlier, click `Ok`.
+    - After successfully choosing the `combined.bin` file, click the `Program` button.
+    - After the TinyUF2 firmware update is complete, press the `RST` button. A new drive `S2MINIBOOT` should be visible in your file browser.
+
+### Flashing CircuitPython
+
+- Flash the UF2 bootloader using the instruction above.
+- Download the `.UF2` file from this page.
+- Drag & Drop the `.UF2` file to the `S2MINIBOOT` drive.
+
 ## Purchase
 
 * [AliExpress](https://www.aliexpress.com/item/1005003145192016.html)