FL2440无操作系统应用程序编写测试004——PWM_TIMER

Subject：FL2440无操作系统应用程序编写测试004——PWM_TIMER
Date： 8-Nov-2011

By： Calvinlee1984@163.com

1.硬件原理图



2. Buzzer寄存器设置

static void Buzzer_Port_Init(void){

//设置GPB0为PWM output

rGPBCON &= ~(0x3);

rGPBCON |= 0x2; //GPB0=TOUT0



//设置GPB0 Pull up function disabled

rGPBUP |= 0x1; //Pull up function disabled

}

3.TIMER0 控制框图



4.TIMER0寄存器设置

static void TIMER0_Port_Init(void){

//设置预分频器

rTCFG0 &= ~(0xff<<0);

rTCFG0 |= (0x3<<0); //prescaler 3+1



//设置分频比

rTCFG1 &= ~(0xf<<0);

rTCFG1 |= (0<<0); //mux = 1/2



//设置控制方式：Disable dead zone、Auto reload、Inverter off、Update TCNTB0 & TCMPB0、Stop

rTCON &=(0x1f<<0) ;

rTCON |= (0xa<<0); //01010



}

5.Auto-reload方式分析

当计数器TCNT减为0时，Auto-reload自动将计数缓冲器TCNTBn的数值拷贝到计数器TCNTn中。如果Auto-reload功能未使能，当TCNTn减为0时，TCNTn将停止计数。



6.代码分析 TIMER.c

#include "2440addr.h"

#include "option.h" //PCLK

#include "UART.h" //UART0_Printf()

//Buzzer寄存器设置

static void Buzzer_Port_Init(void){

rGPBCON &= ~(0x3);

rGPBCON |= 0x2; //GPB0=TOUT0

rGPBUP |= 0x1; //Pull up Function disabled

}

//TIMER0寄存器设置

static void TIMER0_Port_Init(void){

rTCFG0 &= ~(0xff<<0);

rTCFG0 |= (0x3<<0); //prescaler 3+1

rTCFG1 &= ~(0xf<<0);

rTCFG1 |= (0<<0); //mux = 1/2

rTCON &= ~(0x1f<<0);

rTCON |= (0xa<<0); //01010

}

//PWM输出频率设置

static void Buzzer_Frequency_Set(int Freq){

//定时时间为 (PCLK>>3)/(Freq)/(PCLK/8) = 1/(Freq)s

U32 val = (PCLK>>3)/(Freq+1000) - 1;

rTCNTB0 = val;



//PWM占空比

rTCMPB0 = val>>1; //50%方波输出



}

//启动TIMER0

static void TIMER0_Start(void){

rTCON |= (0x1<<0); //Start Timer0

rTCON &= ~(2<<0);



}

//停止TIMER0并关闭Buzzer

static void TIMER0_Stop(void){

rTCON &=(0xfffe<<0); //Stop Timer0

//关闭Buzzer

rGPBCON &= ~(0x3);

rGPBCON |= 0x1; //GPB0=OUTPUT

rGPBDAT &= ~(0x1); //Shut Buzzer

}

void Buzzer_PWM_Test(void){

U8 TmpChar;

int TmpFreq=1000;

Buzzer_Port_Init(); //Buzzer端口寄存器设置

TIMER0_Port_Init(); //TIMER0端口寄存器设置

Buzzer_Frequency_Set(TmpFreq); //PWM输出频率设置

TIMER0_Start(); //启动TIMER0

UART0_Printf("Press +/- to add/dec Frequency of Buzzer and ESC to exit\n");

//根据按键增大或减小PWM输出频率，或退出

while((TmpChar=UART0_GetKey())!=ESC_KEY)

{

if(TmpChar=='+')

{

if(TmpFreq<=2000)

Buzzer_Frequency_Set(TmpFreq+=100);

}

else

{

if(TmpChar=='-')

{

if(TmpFreq>=1000)

Buzzer_Frequency_Set(TmpFreq-=100);

}

}

}

TIMER0_Stop(); //停止TIMER0

}

7. 测试程序及结果

#include "UART.h"

#include "TIMER.h"

int Main(void)

{

UART0_Port_Init(115200); //UART0初始化

Buzzer_PWM_Test(); //PWM输出驱动蜂鸣器

while(1){

;

}

return 0;

}



按+/-增大/减小PWM的输出频率，蜂鸣器发出的声音也随之改变。