如果您想使用iPod连接器连接硬件，那么选项是外部附件框架。请注意，您必须是注册附属开发人员（比标准开发人员许可证更贵）。

If you want to use the iPod connector to connect to your hardware, the only option is the External Accessory framework. Be advised that you must be a registered accessory developer (more expensive than the standard developer license).

我相信Square使用音频输入（其他人可能会纠正我），巧妙的黑客，不需要使用iPod连接器。如果您的硬件可以通过（模拟）音频输入/输出操作，那么可能需要考虑这一点。

I believe Square uses the audio input (others may correct me), an ingenious hack that doesn't require use of the iPod connector. If your hardware can operate over (analog) audio in/out, that might be an option to consider.