PWM-脉宽调制。我的理解是通过控制一个计数器来实现不同脉宽的输出，从而驱动蜂鸣器发出不同的声音。
本实验用到的寄存器如下：
GPBCON -- I/O端口配置寄存器 B
00=Input 01=Output 10=PWM 11=Reserved
GPBDAT -- I/O端口数据寄存器 B
GPFUP --I/O端口上拉电阻使能寄存器 B
0=Enable 1=Disabled
TCFG0 -- 时钟配置寄存器0 (主要是设置预分频）
定时器输入时钟频率=PCLK/{预分频}/{分割值}
{预分频}=1~255
{分割值}=2，4，8，16，32
Address: 0x51000000
Reset value:0x00000000
[7:0]:These 8 bits determine prescaler value for Timer0 and 1
TCFG1 --时钟配置寄存器1(主要是设置分割值）
Address: 0x51000004
Reset value:0x00000000
[3:0]:Select MUX input for PWM Timer0
0000=1/2 0001=1/4 0010=1/8
0011=1/16 01XX=External TCLK0
TCON -- 时钟控制寄存器
Address:0x51000008
Reset value:0x00000000
[0]: Determine start/stop for Timer0 （设置启动/停止）
0=Stop 1=Start for Timer0
[1]: Determine the manual update for Timer0 （设置允许手动修改计数）
0=No operation 1=Update TCNTB0 & TCMPB0
[2]: Determine the output inverter on/off for Timer0 （设置中断）
0=Inverter off 1=Inverter on for TOUT0
[3]: Determine auto reload on/off for timer0
0=One-shot 1=Interval mode(auto reload)
[4]: Determine the dead zone operation
0=Disable 1=Enable
TCNTB0 -- timer0计数缓存寄存器
Address:0x5100000c
Reset value:0x00000000
[15:0]:Set count buffer value for Timer0
TCMPB0 -- timer0比较缓存寄存器
Address:0x51000010
Reset value:0x00000000
[15:0]:Set compare buffer value for Timer0
实验方法：
1.按下k1键，使TOUT0递增占空比
2.按下k2键，使TOUT0递减占空比
3.按下k3键，停止输出
//代码1---参考阿南的例子，这个简单
#include "2410addr.h"
#define KEY1 (1<<1) // rGPF[1] =1 ;
#define KEY2 (1<<4) // rGPF[4] =1 ;
#define KEY3 (1<<2) // rGPF[2] =1 ;
unsigned short freq =0;
//===========================[ SYSTEM ]===================================================
//static int delayLoopCount = 400;
static int delayLoopCount = FCLK/10000/10;
void Delay(int time)
{
// time=0: adjust the Delay function by WatchDog timer.
// time>0: the number of loop time
// resolution of time is 100us.
int i,adjust=0;
if(time==0)
{
time = 200;
adjust = 1;
delayLoopCount = 400;
//PCLK/1M,Watch-dog disable,1/64,interrupt disable,reset disable
rWTCON = ((PCLK/1000000-1)<<8)|(2<<3);
rWTDAT = 0xffff; //for first update
rWTCNT = 0xffff; //resolution=64us @any PCLK
rWTCON = ((PCLK/1000000-1)<<8)|(2<<3)|(1<<5); //Watch-dog timer start
}
for(;time>0;time--)
for(i=0;i<delayLoopCount;i++);
if(adjust==1)
{
rWTCON = ((PCLK/1000000-1)<<8)|(2<<3); //Watch-dog timer stop
i = 0xffff - rWTCNT; //1count->64us, 200*400 cycle runtime = 64*i us
delayLoopCount = 8000000/(i*64); //200*400:64*i=1*x:100 -> x=80000*100/(64*i)
}
}
void PWM_Ini(unsigned short cycle,unsigned short duty){
if(duty > cycle) duty = cycle;
//定时器输入时钟频率=PCLK/{预分频}/{分割值}
rTCFG0 =0x64; //设置预分频为100
rTCFG1 =0x0;//设置分割值为1/2
rTCNTB0 =cycle;
rTCMPB0 =duty;
rTCON = 0x0A;//disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, stop timer 0
//000 01010
rTCON = 0x09;//disable deadzone, auto-reload, inv-off, no operation, start timer 0
//1001
}
void PWM_Stop(){
freq = 2000;
rGPBCON = 0x0;
rGPBDAT = 0x0;
}
void PWM_Output(int number){
if ( number > 0 ){
if ( freq < 255 )
freq += 16;
else
freq = 0;
}
if ( number < 0 ){
if ( freq >= 16 )
freq -= 16;
else
freq = 0;
}
rTCMPB0=freq;
}
void Main(void){
rGPFUP = 0xf800;// KEY [7:0] => PU En
rGPFCON=0xfcc0; //KEY[7:0] => INPUT;
rGPBCON = 0x0;
rGPBCON = 0x02;//TOUT0为输出端口
PWM_Ini(255,freq);
Delay(0);
while (1){
if ( !(rGPFDAT & KEY1) ){
Delay(1000);
//if (rGPGDAT & KEY1) continue;
PWM_Output(1);
}
if ( !(rGPFDAT & KEY2) ){
Delay(1000);
//if (rGPGDAT & KEY2) continue;
PWM_Output(-1);
}
if ( !(rGPFDAT & KEY3) ){
Delay(1000);
//if (rGPGDAT & KEY3) continue;
PWM_Stop();
}
}
}
上面的例子就是按键去抖功能没能调试出来。
//代码2---参考开发板带的例子，这个不好理解
#define GLOBAL_CLK 1
#include "def.h"
#include "2440addr.h"
#include "option.h"
#define KEY1 (1<<1) // rGPF[1] =1 ;
#define KEY2 (1<<4) // rGPF[4] =1 ;
#define KEY3 (1<<2) // rGPF[2] =1 ;
static unsigned int freq;
void PWM_Ini(){
ChangeClockDivider(3,1); //获得PCLK=67.5MHz
ChangeMPllValue(127,2,1);
rGPFUP = 0xf800;// KEY [7:0] => PU En
rGPFCON=0xfcc0; //KEY[7:0] => INPUT;
}
void PWM_Stop(){
freq = 2000;
rGPBCON = 0x0;
rGPBDAT = 0x0;
}
void PWM_Output(int number){
rGPBCON = 0x0;
rGPBCON = 0x02;//TOUT0为输出端口
//rGPBUP = 0x01;//禁止上拉电阻
//定时器输入时钟频率=PCLK/{预分频}/{分割值}
rTCFG0 =0x64; //设置预分频为100
rTCFG1 =0x0;//设置分割值为1/2
if ( number > 0 ){
if ( freq < 20000 )
freq += number;
else
freq = 2000;
}
if ( number < 0 ){
if ( freq > 300 )
freq -= number;
else
freq = 2000;
}
rTCNTB0 =freq;
rTCMPB0 =rTCNTB0>>1;
rTCON = 0x0B;//disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0
//000 01011
rTCON &= ~2;//clear manual update bit
}
void Main(void){
freq = 2000;
PWM_Ini();
while (1){
if ( !(rGPFDAT & KEY1) )
PWM_Output(100);
if ( !(rGPFDAT & KEY2) )
PWM_Output(-100);
if ( !(rGPFDAT & KEY3) )
PWM_Stop();
}
}
这个例子每次都要重新设置PGB端口。