Update the README.md

Writing the README to make people interested and understand this repo.

README.md

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-# STM32_Platform
+# STM32_Platform
+
+##Introduction
+The STM32 platform integrates a MCU, a BLE transmitter(BlueNRG), and several sensors manufactured by STMicroelectronics.
+
+This repository includes a comprehensive SDK together with various software resources like drivers, middlewares, examples for STM32 platform development.
+
+
+##Cannon
+* Cannon is one of the development boards belongs to STM32 platform. 
+* Cannon boards allow anyone to try out new ideas and to quickly create prototypes.
+* Learn hardware specs at: [http://www.juma.io/platform/cannon.html](http://www.juma.io/platform/cannon.html)
+* Learn software usages at: [http://www.juma.io/doc/zh/boards/st/cannon.html](http://www.juma.io/doc/zh/boards/st/cannon.html)
+* Learn software API manuals at: [http://www.juma.io/doc/zh/embedded_sdk.html](http://www.juma.io/doc/zh/embedded_sdk.html)
+* Get a Cannon board at JUMA's Taobao shop: [http://tao.bb/5Dh6u](http://tao.bb/5Dh6u)
+
+##Directories
+* /product - several examples based on Cannon, including a Thermometer detector, a BLE echo appliction, a SensorTag, etc. 
+* /system - including drivers, HALs, middlewares, JUMA SDKs, etc.
+* /tool - including some APP utilities which could be installed and run on Andoird mobiles. 
+* /document - things like document, datasheet, manuals, etc.
+
+
+##Quick Start
+1. Choose seed project 
+Learn examples under */product* folder, select one to be the seed project. 
+Copy & pasta it to create your own project.
+
+2. Header files 
+Remember to include necessary header files. 
+For BLE, it is: */system/juma/inc/bluenrg_sdk_api.h* 
+For sensors, it is: */system/juma/inc/juma_sensor.h*
+
+3. Make your own application 
+Modify the seed project, change the logics, flows, algorithms, etc. 
+Make it fit to your own application.
+
+4. Compile firmware 
+Cannon board has two versions, select the right one in Keil compile option.
+
+5. Download firmware 
+Connect Cannon to computer via J-Link or ST-LINK. 
+Keil can download firmware to Cannon.
+
+6. Work with BLE APP 
+To facilitate BLE development, we offered a BLE debugger AP in */tool* folder. 
+It can be run on Android moilbe to transmit BLE raw data to/from Cannon.
+
+
+##Further Resources
+* Home: [http://www.juma.io](http://www.juma.io)
+* Contact: [[email protected]]([email protected])