arm7 键盘扫描程序

以下是一个简单的 ARM7 键盘扫描程序示例，可以检测按下的键并将其输出：

#include<lpc214x.h>

#define KEYPAD_PORT 0x000000F0 // P0.4 ~ P0.7

void delay(unsigned int count)
{
    unsigned int i,j;
    for(i=0;i<count;i++)
    {
        for(j=0;j<1000;j++);
    }
}

int main()
{
    unsigned char keypad[4][4] = {{'1','2','3','A'},
                                  {'4','5','6','B'},
                                  {'7','8','9','C'},
                                  {'*','0','#','D'}};
    unsigned char row,col;
    unsigned char key;
  
    IO0DIR = 0x000000F0; // P0.4 ~ P0.7 as input
    IO0CLR = KEYPAD_PORT; // Clear keypad output pins
  
    while(1)
    {
        for(row=0;row<4;row++)
        {
            IO0SET = (1<<(row+4)); // Set row pin high
            delay(10); // Wait for row pin to stabilize
            col = ((IO0PIN & KEYPAD_PORT) >> 4); // Read column pins
            if(col != 0x0F) // Key pressed
            {
                key = keypad[row][col]; // Get the key value
                while((IO0PIN & KEYPAD_PORT) != 0x0F); // Wait for key release
                printf("%c\n",key); // Output the key value
            }
            IO0CLR = (1<<(row+4)); // Set row pin low
        }
    }
    return 0;
}

该程序使用了一个 4x4 的矩阵键盘，将其连接到了 ARM7 的 P0.4 ~ P0.7 引脚上。程序会轮询四行四列按键的状态，并在检测到按键按下时输出对应的键值。注意，在实际使用中可能需要根据具体的硬件连接进行适当修改。