#include <reg52.h>
sbit PWMOUT = P0^0;
sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;
unsigned long PeriodCnt = 0; //PWM周期计数值
unsigned char HighRH = 0; //高电平重载值的高字节
unsigned char HighRL = 0; //高电平重载值的低字节
unsigned char LowRH = 0; //低电平重载值的高字节
unsigned char LowRL = 0; //低电平重载值的低字节
unsigned char T1RH = 0; //T1重载值的高字节
unsigned char T1RL = 0; //T1重载值的低字节
void ConfigTimer1(unsigned int ms);
void ConfigPWM(unsigned int fr, unsigned char dc);
void main()
{
EA = 1; //开总中断
ENLED = 0; //使能独立LED
ADDR3 = 1;
ADDR2 = 1;
ADDR1 = 1;
ADDR0 = 0;
ConfigPWM(100, 10); //配置并启动PWM
ConfigTimer1(50); //用T1定时调整占空比
while (1);
}
/* 配置并启动T1，ms-定时时间 */
void ConfigTimer1(unsigned int ms)
{
unsigned long tmp; //临时变量
tmp = 11059200 / 12; //定时器计数频率
tmp = (tmp * ms) / 1000; //计算所需的计数值
tmp = 65536 - tmp; //计算定时器重载值
tmp = tmp + 12; //补偿中断响应延时造成的误差
T1RH = (unsigned char)(tmp>>8); //定时器重载值拆分为高低字节
T1RL = (unsigned char)tmp;
TMOD &= 0x0F; //清零T1的控制位
TMOD |= 0x10; //配置T1为模式1
TH1 = T1RH; //加载T1重载值
TL1 = T1RL;
ET1 = 1; //使能T1中断
TR1 = 1; //启动T1
}
/* 配置并启动PWM，fr-频率，dc-占空比 */
void ConfigPWM(unsigned int fr, unsigned char dc)
{
unsigned int high, low;
PeriodCnt = (11059200/12) / fr; //计算一个周期所需的计数值
high = (PeriodCnt*dc) / 100; //计算高电平所需的计数值
low = PeriodCnt - high; //计算低电平所需的计数值
high = 65536 - high + 12; //计算高电平的定时器重载值并补偿中断延时
low = 65536 - low + 12; //计算低电平的定时器重载值并补偿中断延时
HighRH = (unsigned char)(high>>8); //高电平重载值拆分为高低字节
HighRL = (unsigned char)high;
LowRH = (unsigned char)(low>>8); //低电平重载值拆分为高低字节
LowRL = (unsigned char)low;
TMOD &= 0xF0; //清零T0的控制位
TMOD |= 0x01; //配置T0为模式1
TH0 = HighRH; //加载T0重载值
TL0 = HighRL;
ET0 = 1; //使能T0中断
TR0 = 1; //启动T0
PWMOUT = 1; //输出高电平
}
/* 占空比调整函数，频率不变只调整占空比 */
void AdjustDutyCycle(unsigned char dc)
{
unsigned int high, low;
high = (PeriodCnt*dc) / 100; //计算高电平所需的计数值
low = PeriodCnt - high; //计算低电平所需的计数值
high = 65536 - high + 12; //计算高电平的定时器重载值并补偿中断延时
low = 65536 - low + 12; //计算低电平的定时器重载值并补偿中断延时
HighRH = (unsigned char)(high>>8); //高电平重载值拆分为高低字节
HighRL = (unsigned char)high;
LowRH = (unsigned char)(low>>8); //低电平重载值拆分为高低字节
LowRL = (unsigned char)low;
}
/* T0中断服务函数，产生PWM输出 */
void InterruptTimer0() interrupt 1
{
if (PWMOUT == 1) //当前输出为高电平时，装载低电平值并输出低电平
{
TH0 = LowRH;
TL0 = LowRL;
PWMOUT = 0;
}
else //当前输出为低电平时，装载高电平值并输出高电平
{
TH0 = HighRH;
TL0 = HighRL;
PWMOUT = 1;
}
}
/* T1中断服务函数，定时动态调整占空比 */
void InterruptTimer1() interrupt 3
{
static bit dir = 0;
static unsigned char index = 0;
unsigned char code table[13] = { //占空比调整表
5, 18, 30, 41, 51, 60, 68, 75, 81, 86, 90, 93, 95
};
TH1 = T1RH; //重新加载T1重载值
TL1 = T1RL;
AdjustDutyCycle(table[index]); //调整PWM的占空比
if (dir == 0) //逐步增大占空比
{
index++;
if (index >= 12)
{
dir = 1;
}
}
else //逐步减小占空比
{
index--;
if (index == 0)
{
dir = 0;
}
}
}
追问怎么样才能手动调节占空比