SIM300硬件电路及应用说明（中英文版），包含英文：SIM300原理图，命令讲解，硬件。中文：详细使用说明，如何连接，如何传输数据。本人亲自整理-SIM300 hardware circuits and application notes (in English), including English: SIM300 schematic diagram, the order on the hardware. Chinese: detailed instructions, how to conn