diff --git a/README.md b/README.md
index 9da2d38..e22e4ad 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # MYNT® EYE SDK
 
-[![](https://img.shields.io/badge/MYNT%20EYE%20SDK-2.0.1--rc2-brightgreen.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2)
+[![](https://img.shields.io/badge/MYNT%20EYE%20SDK-2.2.1--rc-brightgreen.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2)
 
 ## Overview
 
@@ -17,11 +17,11 @@ Please follow the guide doc to install the SDK on different platforms.
 ## Documentations
 
 * [API Doc](https://github.com/slightech/MYNT-EYE-SDK-2/releases): API reference, some guides and data spec.
-  * en: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2422149/mynt-eye-sdk-apidoc-2.0.1-rc2-en.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2422151/mynt-eye-sdk-apidoc-2.0.1-rc2-html-en.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](https://slightech.github.io/MYNT-EYE-SDK-2/)
-  * zh-Hans: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2422152/mynt-eye-sdk-apidoc-2.0.1-rc2-zh-Hans.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2422153/mynt-eye-sdk-apidoc-2.0.1-rc2-html-zh-Hans.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](http://doc.myntai.com/resource/api/mynt-eye-sdk-apidoc-2.0.1-rc2-html-zh-Hans/mynt-eye-sdk-apidoc-2.0.1-rc2-html-zh-Hans/index.html)
+  * en: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2501756/mynt-eye-sdk-apidoc-2.2.1-rc-en.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2501763/mynt-eye-sdk-apidoc-2.2.1-rc-en.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](https://slightech.github.io/MYNT-EYE-SDK-2/)
+  * zh-Hans: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2501770/mynt-eye-sdk-apidoc-2.2.1-rc-zh-Hans.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2/files/2501782/mynt-eye-sdk-apidoc-2.2.1-rc-zh-Hans.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](http://doc.myntai.com/resource/api/mynt-eye-sdk-apidoc-2.2.1-rc-zh-Hans/mynt-eye-sdk-apidoc-2.2.1-rc-zh-Hans/index.html)
 * [Guide Doc](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/releases): How to install and start using the SDK.
-  * en: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2422160/mynt-eye-sdk-guide-2.0.1-rc2-en.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2422161/mynt-eye-sdk-guide-2.0.1-rc2-html-en.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](https://slightech.github.io/MYNT-EYE-SDK-2-Guide/)
-  * zh-Hans: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2422162/mynt-eye-sdk-guide-2.0.1-rc2-zh-Hans.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2422164/mynt-eye-sdk-guide-2.0.1-rc2-html-zh-Hans.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](http://doc.myntai.com/resource/sdk/mynt-eye-sdk-guide-2.0.1-rc2-html-zh-Hans/mynt-eye-sdk-guide-2.0.1-rc2-html-zh-Hans/index.html)
+  * en: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2501821/mynt-eye-sdk-guide-2.2.1-rc-en.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2501822/mynt-eye-sdk-guide-2.2.1-rc-en.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](https://slightech.github.io/MYNT-EYE-SDK-2-Guide/)
+  * zh-Hans: [![](https://img.shields.io/badge/Download-PDF-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2501823/mynt-eye-sdk-guide-2.2.1-rc-zh-Hans.pdf) [![](https://img.shields.io/badge/Download-HTML-blue.svg?style=flat)](https://github.com/slightech/MYNT-EYE-SDK-2-Guide/files/2501827/mynt-eye-sdk-guide-2.2.1-rc-zh-Hans.zip) [![](https://img.shields.io/badge/Online-HTML-blue.svg?style=flat)](http://doc.myntai.com/resource/sdk/mynt-eye-sdk-guide-2.2.1-rc-zh-Hans/mynt-eye-sdk-guide-2.2.1-rc-zh-Hans/index.html)
 
 > Supported languages: `en`, `zh-Hans`.
 
@@ -29,7 +29,7 @@ Please follow the guide doc to install the SDK on different platforms.
 
 [MYNTEYE_BOX]: http://doc.myntai.com/mynteye/s/download
 
-Get firmwares from our online disks: [MYNTEYE_BOX][]. The latest version is `2.0.1`.
+Get firmwares from our online disks: [MYNTEYE_BOX][]. The latest version is `2.2.1`.
 
 ## Usage