【求助】PWM转DA输出WAV音频的一个小程序-第16页回答

【求助】PWM转DA输出WAV音频的一个小程序

2020-01-12 17:25发布

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99条回答

wicy001

1楼-- · 2020-01-23 12:38

gamethink 发表于 2013-6-13 14:27
请教LZ，WAV记录的音频数据是有分正/负的，比如8位，究竟如何和PWM的0-255关联起来？ ...

你好，WAV中的数据代表了电压的高低（电压的高低由PWM控制），进而表示为喇叭震动的振幅。

所以：正负数据，与0-255线性对应即可。

gamethink

2楼-- · 2020-01-23 16:52

精彩回答 2 元偷偷看……

bg4gzu

3楼-- · 2020-01-23 22:29

RC滤波改为LC滤波。
效果会好一些。电感可选用33uH，对地电容用0.47uF左右。可以适当增加电感来改变低通频率。

vbvc6

4楼-- · 2020-01-24 04:21

我用LMF4L120试了下,效果差的很,有很明显的尖噪音,我直接用IO驱动蜂鸣器,接音响效果好点,但噪声依然很大
50M/256 等效约200k的DA

void BeepLevelSet(int level);

#define VOICE_TIMER SYSCTL_PERIPH_TIMER2
#define VOICE_TIMER_BASE       TIMER2_BASE
#define VOICE_GPIO_PIN_CFG    GPIO_PB0_T2CCP0
#define VOICE_GPIO_PIN       GPIO_PIN_0
#define VOICE_GPIO_PERIPH    SYSCTL_PERIPH_GPIOB
#define VOICE_GPIO_BASE    GPIO_PORTB_BASE

static unsigned int BufferPosMax=0;
static unsigned char *WaveBufferStart=0;

void IntTimer5HandlerA(void)
{
static unsigned int BufferPos;
HWREG(TIMER5_BASE + TIMER_O_ICR) = 0x01;
if(0==WaveBufferStart){
BufferPos=0;
return;
}
BeepLevelSet(WaveBufferStart[BufferPos]);
BufferPos++;
if(BufferPos>=BufferPosMax){
BufferPos=0;
WaveBufferStart=0;
}
return;
}
void BeepInit(void)
{
//
// Enable the GPIO Port and Timer for each LED
//
SysCtlPeripheralEnable(VOICE_GPIO_PERIPH);
SysCtlPeripheralEnable(VOICE_TIMER);
GPIOPinTypeGPIOOutput(GPIO_PORTB_BASE,GPIO_PIN_0);
//
// Configure each timer for output mode
//
HWREG(VOICE_TIMER_BASE + TIMER_O_CTL) = 0x00;
HWREG(VOICE_TIMER_BASE + TIMER_O_CFG) = 0x04;
HWREG(VOICE_TIMER_BASE + TIMER_O_TAMR)  = 0x0A;
HWREG(VOICE_TIMER_BASE + TIMER_O_TAILR) = 0xFF;

//
// Invert the output signals.
//
HWREG(VOICE_TIMER_BASE + TIMER_O_CTL) |= 0x40;
//
// Enable timers to begin counting
//
TimerEnable(VOICE_TIMER_BASE, TIMER_A);
//
// Reconfigure each LED's GPIO pad for timer control
//
GPIOPinConfigure(VOICE_GPIO_PIN_CFG);
GPIOPinTypeTimer(VOICE_GPIO_BASE, VOICE_GPIO_PIN);
GPIOPadConfigSet(VOICE_GPIO_BASE, VOICE_GPIO_PIN, GPIO_STRENGTH_2MA,
                  GPIO_PIN_TYPE_STD);

BeepLevelSet(0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER5);
HWREG(TIMER5_BASE + TIMER_O_CTL) = 0x00;
HWREG(TIMER5_BASE + TIMER_O_CFG) = 0x04;
HWREG(TIMER5_BASE + TIMER_O_TAMR)  = 0x02;
HWREG(TIMER5_BASE + TIMER_O_TAILR) = 0x186A; //8000
TimerMatchSet(TIMER5_BASE,TIMER_A,2);
TimerEnable(TIMER5_BASE, TIMER_A);
TimerIntEnable(TIMER5_BASE,TIMER_TIMA_TIMEOUT);//TIMER_TIMA_MATCH //TIMER_TIMA_TIMEOUT
IntEnable(INT_TIMER5A);
}

void BeepLevelSet(int level)
{
TimerMatchSet(VOICE_TIMER_BASE,TIMER_A,level);
}

void TestWaveOut(void)
{
BufferPosMax=sizeof(wave_data);
WaveBufferStart=(unsigned char*)wave_data;
}