So the Accessory Development Kit from Google is open-source and based on Arduino, as opposed to the one from Apple which is closed-source, NDA, sign your life to Apple. Here you are.
这个开发套件来自谷歌 同样也是开源的 并且基于Arduino 而苹果公司的产品 则是非开源的，受保密协议保护 要跟苹果公司签合同