網上流傳不同的PSP自制鍵盤研發, 這次介紹的是一個完全不用更改PSP的研發方法 - 把USB接口改成PSP的接口.
以下是部份內容, 想參看全文請按下面的來源連結:

I currently have completed the USB mouse driver and a USB Keyboard driver. I am currently debugging the gamepad drivers for the XBOX 360 wireless gamepad, the PS2/PS3 wireless gamepad, and the Logitech Wingman wireless gamepad.

Now that you have seen it, I will also say that yes I have tested a USB hard drive on this interface and can we say Sloooooooooooow.

It was never intended to do hard drives through the serial port anyway, but I did it to say yes it can be done. Besides I had the driver code for a mass storage device.

重點翻譯:
制作人已經完成制作USB鍵盤和鼠標的驅動程序, 但還有以下的程序有待研發: XBOX 360 wireless gamepad, the PS2/PS3 wireless gamepad, and the Logitech Wingman wireless gamepad.
另外, USB硬盤也能支持, 但讀寫速度慢得很. 還有待日後改良.

此研發程序還正在研發中, 未來得到的訊息將在此公佈.

來源: 參看文章 (ps2dev)