Update README.md

Author: d-kato

README.md

@@ -2,8 +2,11 @@
 The Mbed OS driver for the ESP32 WiFi module.
 
 ## Firmware version
-How to write mbed-os compatible firmware :
+How to write mbed-os compatible firmware for GR-LCYHEE and GR-PEACH.  
 https://github.com/d-kato/GR-Boards_ESP32_Serial_Bridge
 
+## Mbed OS BLE stack using ESP32
+You can use the Mbed OS BLE stack with ESP32 by using [esp32-at-ble-stack.lib](https://github.com/d-kato/esp32-at-ble-stack).
+
 ## Restrictions
 - Setting up an UDP server is not possible