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问 我想用PWM作为按键声输出.其中分为两种按键声:1000Hz,和500Hz.
利用LPC2114第一脚的PWM5驱动蜂鸣器.代码如下:
//*************************************************
//*************************************************
#define BUZ_FREQ_DI    1000    //Di声的频率(Hz)
#define BUZ_FREQ_DU    500        //Du声的频率(Hz)
#define BUZ_DI_TIME    100        //Di声的时间长度(ms)
#define BUZ_DU_TIME    100        //Du声的时间长度(ms)
//*************************************************
//*************************************************
void BuzzerInit(void)
{
    //设置Pin1为PWM输出.
    PINSEL1 &= PS_P021_SET;
    PINSEL1 |= PS_P021_PWM5;
    PWMPR = 0x00;                // 不分频,计数频率为Fpclk
    PWMMCR = 0x02;                // 设置PWMMR0匹配时复位PWMTC
}
//*************************************************
//*************************************************
void BuzzerDi(void)
{    
    PWMPCR = 0;                    
    PWMTCR = 0;
    PWMMR0 = Fpclk/BUZ_FREQ_DI; // 设置PWM周期,(Buzzer Freq. = BUZ_FREQ_DI Hz)
    PWMMR5 = PWMMR0/2;            // 设置PWM占空比=50%
    PWMLER = 0x21;                // PWMMR0,PWMMR5锁存
    PWMPCR = 0x2000;            // 允许PWM5输出,单边PWM
    PWMTCR = 0x09;                // 启动定时器，PWM使能
    BuzTimer = BUZ_DI_TIME/20;    // BuzzerTimer()每20ms调用一次
}
//*************************************************
//*************************************************
void BuzzerDu(void)
{
    PWMPCR = 0;                
    PWMTCR = 0;
    PWMMR0 = Fpclk/BUZ_FREQ_DU;    // 设置PWM周期,(Buzzer Freq. = BUZ_FREQ_DU Hz)
    PWMMR5 = PWMMR0/2;            // 设置PWM占空比=50%
    PWMLER = 0x21;                // PWMMR0,PWMMR5锁存
    PWMPCR = 0x2000;            // 允许PWM5输出,单边PWM
    PWMTCR = 0x09;                // 启动定时器，PWM使能
    BuzTimer = BUZ_DU_TIME/20;    // BuzzerTimer()每20ms调用一次
}
//*************************************************
// 时间到,停止PWM输出.
//*************************************************
void BuzzerTimer(void)
{
    if (BuzTimer > 0)
    {
        BuzTimer--;
        if (BuzTimer == 0)
        {
            PWMPCR = 0;
            PWMTCR = 0;
        }
    }
}

系统开机时调用BuzzerInit()初始化,要发1000Hz的声音调用BuzzerDi(),500Hz的声音调用BuzzerDu().现在遇到的问题是.如果频繁性交叉地调用两种声音,会出现不出声的情况.必须Reset后才会恢复正常.但是频繁地调用一种声音.不会出现这样的情况.希望各位大侠帮我看看.哪里有问题?多谢大家了! 答 1: 在关闭PWM的同时，复位PWM计数器即
PWMTCR=0x02;
PWMTCR=0x00; 答 2: 谢谢.果然是如此.