用于打印qwerty键的9键键盘的逻辑

Question

我有一个设备,有一个像普通手机一样的9键.我想使用这9个键来打印像ABCD这样的普通字母,就像手机让你这样做一样.

这是一个嵌入式系统编程项目.我无法弄清楚实现此功能的逻辑.

我通过轮询而不是通过中断来检测密钥.

有人可以帮忙吗？如果你能指出相关资源,我将不胜感激.

Answer 1

这是一个小键盘解码演示,可以帮助您顺利完成.您需要重写硬件的密钥扫描例程.此外,连续两次选择相同的数字需要某种超时.您还应该在确定如何添加对大小写,标点符号和元键的支持方面遇到一些麻烦......

#include <stdio.h>

#define NUM_KEYS 10
#define NUM_PHASES 6

char KeyMap[NUM_KEYS][NUM_PHASES] =
    {   { '0',   0,   0,   0,   0,   0 },
        { '1',   0,   0,   0,   0,   0 },
        { '2', 'A', 'B', 'C',   0,   0 },
        { '3', 'D', 'E', 'F',   0,   0 },
        { '4', 'G', 'H', 'I',   0,   0 },
        { '5', 'J', 'K', 'L',   0,   0 },
        { '6', 'M', 'N', 'O',   0,   0 },
        { '7', 'P', 'Q', 'R', 'S',   0 },
        { '8', 'T', 'U', 'V',   0,   0 },
        { '9', 'W', 'X', 'Y', 'Z',   0 }    };

char KeyGet()
{
    char key;

    /* do whatever it takes to scan your
       keyboard and return the _numeric_ digit. */

    /* for this test simulate with console input */
    key = getc(stdin);

    if ((key >= '0') && (key <= '9'))
    {
        key -= 0x30;
    }
    else
    {
        key = 0;
    }

    return key;
}

char DecodeKey(char NewKey, char *pOldKey, int *pPhase)
{
    char ch = 0;

    /* Validate Phase */
    if ((*pPhase < 0) || (*pPhase >= NUM_PHASES))
    {
        *pPhase = 0;
    }

    /* see if a different key was pressed than last time */
    /* if it was then restart the phase counter */
    if (NewKey != *pOldKey)
    {
        *pPhase = 0;
        *pOldKey = NewKey;
    }

    /* Validate Key */
    if ((NewKey >= 0) && (NewKey < NUM_KEYS))
    {
        ch = KeyMap[(int)NewKey][*pPhase];

        /* if the phase position is NULL, just get the numeric digit */
        if (ch == 0)
        {
            *pPhase = 0;
            ch = KeyMap[(int)NewKey][*pPhase];
        }

        /* bump the phase */
        ++(*pPhase);

        if (*pPhase >= NUM_PHASES)
        {
            *pPhase = 0;
        }
    }

    return ch;
}

int main()
{
    char nk;        /* new key */
    char ok = 0;    /* old key */
    char c;         /* resulting character */
    int phase = 0;  /* tracks the key presses */

    while (1)
    {
        /* get a key */
        nk = KeyGet();

        /* convert it to a character */
        c = DecodeKey(nk, &ok, &phase);

        if (c != 0)
        {
            printf("%c", c);
        }
    }

    return 0;
}