//一个单片机系统的设计经常会用到多种不同目的和用图的定时，例如系统需要输出
//一个指示“心跳正常”的秒闪信号，间隔0.5s；按键检测时临时需要约20ms的消抖；
//蜂鸣器需要发声延时；用户菜单选择时可能需要对应的发光管或LCD点阵（字段）
//闪烁；通讯时需要设定应答超时判别，等等。是不是要抱怨一个单片机上的若干个
//定时器不够用了？其实，用一个定时器资源就可以搞定所有的这一切定时要求。
//1）首先，选定一个你喜欢的定时器，按所需应用的定时精度要求设定其定时中断频
//率。一般人机界面的定时精度为ms级就足够了，所以可以设定定时中断时间间隔为
//1ms，5ms或10ms；例如我的选择：
//==============================================================
// TPM2 overflow interrupt service routine
// Interrupt at every 1ms
//==============================================================
void interrupt 14 TPM2_Overflow_ISR(void)
{
TPM2SC_TOF = 0; //reset interrupt flag
msTimeoutCount++; //1ms increment
}
//变量msTimeoutCount是一个16位word型的静态变量，在中断服务程序中简单地对它
//递增，无需考虑溢出。如果你的中断时间间隔为Nms，则在中断中对其递增的方法为
//“msTimeoutCount += N”。它在程序模块的前面被声明，为了提高中断服务程序的效
//率，其被定位在直接寻址区：
//==============================================================
// Following data are declared in the direct addressing area
// for fast access (address < 0x100)
//==============================================================
#pragma DATA_SEG SHORT MY_ZEROPAGE //direct addressing data segment
volatile word msTimeoutCount;
//然后写一段独立的定时判别函数。这个函数有两个入口参数：特定定时实例的一个
//定时变量指针和所需的定时时间长度。若定时时间长度为0，则定时过程被复位，实
//际上是当前的定时计数器值（msTimeoutCount）被复制到定时实例的一个定时变量
//中。返回值为0则表明定时时间未到，0xff则为一次定时时间到并自动开始下一次的
//定时过程。具体代码如下：
//==============================================================
// Check for timeout occurance
// Input *timer - pointer of timer counter
// timeOutVal - timeout value, 0=forced timer update
// Return 0 - no timeout yet
// 0xff - timeout occured and timer updated
//==============================================================
byte TimeOutChk(word *timer, word timeOutVal)
{
word shadow, diff;
TPM2SC_TOIE = 0; //针对8位机必须禁止定时中断，16位机以上则无需如此
shadow = msTimeoutCount; //将当前时间计数值复制一份以作后需
TPM2SC_TOIE = 1; //对应上面的中断禁止，现在开放中断
if (timeOutVal==0)
{ //复位定时过程
*timer = shadow;
return(0);
}
else
{
diff = shadow - *timer; //计算定时时间间隔
if (diff>=timeOutVal)
{ //定时时间到
*timer += timeOutVal; //更新定时变量，开始下一次定时过程
return(0xff);// 返回时间到标志
}
else
{
return(0); //定时时间未到
}
}
}
//剩下的就看具体应用的需要而开辟特定的定时实例了。每一个实例必须有一个word
//型的变量作为定时跟踪变量。
//例如产生500ms的定时（msCount变量在模块前面已经定义）：
void main(void)
{
...
TimeOutChk(&msCount, 0); //复位初始化定时实例
...
while(1)
{
Clock();
KeyScan();
...
}
}
//==============================================================
// Keep the system clock running
//==============================================================
void Clock(void)
{
if (TimeOutChk(&msCount, 500)==0)
return; //wait for 0.5 second time out
runFlag.halfSec = !runFlag.halfSec;
dispCodeBuff[2] ^= 0x80;
dispCodeBuff[3] ^= 0x80;
if (runFlag.halfSec)
{
return;
}
second++;
if (second==30)
{ //sync soft clock with RTC value
RTC_Read();
}
if (second>59)
{
second = 0;
minute++;
if (minute>59)
{
minute = 0;
hour++;
if (hour>23)
hour = 0;
}
}
runFlag.clkDisp = 1;
}
//按键扫描时的消抖延时实现, keyDebounce在模块前面为局部静态变量定义
//==============================================================
// Scaning key input
//==============================================================
void KeyScan(void)
{
byte keyInput;
keyInput = (PTFD^0xff) & 0b00011111;
switch (keyState)
{
case 0: //idle
if (keyInput)
{ //possible key input detected
runFlag.keyCon = 0; //continuous key strike not allowed by default
TimeOutChk(&keyDebounce, 0); //reset debounce timer
keyState = 1;
}
break;
case 1: //down debouncing
if (TimeOutChk(&keyDebounce, 50))
{ //50ms debounce timeout
if (keyInput)
{
KeyFifoAdd(keyInput);
TimeOutChk(&keyDebounce, 0); //!复位定时准备实现按键持续按下时的连续激发功能
keyState = 2; //key is holding
}
else
{
keyState = 0; //debounce check failed
}
}
break;
case 2: //hold
if (keyInput==0)
{ //possible key release detected
TimeOutChk(&keyDebounce, 0);
keyState = 4;
}
else
{
if (runFlag.keyCon)
{ //continuous key strike allowed
if (TimeOutChk(&keyDebounce, 500))
{ //持续按下时间达0.5s
KeyFifoAdd(keyInput);
TimeOutChk(&keyDebounce, 0); //准备后续每隔0.1s激发一个按键值
keyState = 3; //invoke key continuous strike
}
}
}
break;
case 3: //continuous strike
if (keyInput==0)
{ //possible key release detected
TimeOutChk(&keyDebounce, 0);
keyState = 4;
}
else
{
if (TimeOutChk(&keyDebounce, 100))
{ //每隔0.1s激发一个按键值
KeyFifoAdd(keyInput);
TimeOutChk(&keyDebounce, 0);
}
}
break;
case 4: //up debouncing
if (TimeOutChk(&keyDebounce, 50))
{ //50ms debounce timeout
if (keyInput)
{
keyState = 2; //key is still holding
}
else
{
keyState = 0; //confirm released
}
}
break;
default:
keyState = 0;
}
}
//所以理论上只要你有足够多的内存作为定时跟踪变量，你就可以实现任意多个定时
//实例，无论什么时间和什么地点。当然上面的定时程序有一个局限，就是一次最大
//的定时时间为65535ms。如果要实现更长时间的定时，可以用一个实例产生1s
//（或更长）的定时基准，然后参照函数TimeOutChk另外写一个例如TimeOutChkSec，
//按1s的分辨率最多实现65535s的定时。
//采用状态机实现按键检测是最可靠最有效的方法。同时在单片机设计中实现多任务
//的并发和协调，状态机起着不可或缺的作用。对于按键处理，部分代码如下：
#define KEY_FIFO_LEN 4
byte keyFifo[KEY_FIFO_LEN], keyPut, keyGet;
//==============================================================
// Add a key into FIFO
//==============================================================
void KeyFifoAdd(byte code)
{
keyFifo[keyPut++] = code;
keyPut &= (KEY_FIFO_LEN-1);
}
//==============================================================
// Fetch a key from FIFO
//==============================================================
byte KeyFifoGet(void)
{
byte tmp;
tmp = keyFifo[keyGet++];
keyGet &= (KEY_FIFO_LEN-1);
return(tmp);
}
//==============================================================
// Do key function for primary task
//==============================================================
void KeyFuncMain(void)
{
byte keyCode;
if (keyPut==keyGet)
return;
keyCode = KeyFifoGet();
switch (keyCode)
{
case KEY_CH1_CTL:
RELAY1_CTL = !RELAY1_CTL;
if (RELAY1_CTL)
dispCodeBuff[4] |= 0x10;
else dispCodeBuff[4] &= (0x10^0xff);
SetBeep(200);
break;
case KEY_CH2_CTL:
RELAY2_CTL = !RELAY2_CTL;
if (RELAY2_CTL)
dispCodeBuff[4] |= 0x08;
else dispCodeBuff[4] &= (0x08^0xff);
SetBeep(200);
break;
case KEY_SET:
SetBeep(50);
TimeOutChk(&menuTimeout, 0);
menuId = 0;
MainTaskEntry = SetupEnable;
MenuTaskEntry = ClockSetup;
dispCodeBuff[4] = 0x01;
break;
default:
return;
}
} |
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