使用 2410 实验平台上 4x4 用户键盘，编写程序接收键盘中断。通过 IIC 总线读入键值，并将读到的键值发送到串口。-Experimental platform using the 2410 4x4 user keyboard, write a program to receive the keyboard interrupt. IIC bus read through the key, and read the key sent to the serial port.