ISR +代码，将计数代码与ISR例程集成

Question

我有一段C代码的PIC设备，它启动4个独立的继电器到一个预先定义的模式，每个单独设置通过计数的时间和发生的频率。此模式继续ad-infinitum，但发现标准delay_ms上的计时不够精确。我希望将其转换为ISR例程，我附上了以下依赖于标准延迟的代码供您阅读，我主要关心的是如何将这些代码抽象为ISR，因为我知道不要将所有这些代码都放在实际的ISR例程中，任何建议都非常感谢。

__CONFIG(FOSC_XT & WDTE_OFF & PWRTE_OFF & MCLRE_OFF & CP_OFF & CPD_OFF &
        BOREN_OFF & CLKOUTEN_OFF & IESO_OFF & FCMEN_OFF);

//!!! use BORV_HI for latest PICC compiler
__CONFIG(WRT_OFF & PLLEN_OFF & STVREN_OFF & LVP_OFF);       

#define _XTAL_FREQ  4000000

unsigned long int Sample_Period =20;
unsigned long int Sample_Duration = 2;
unsigned long int Sample_ON = 0;
unsigned long int WriteTX_Period = 21;
unsigned long int WriteTX_Duration = 1; //  
unsigned long int WriteTX_ON = 0;
unsigned long int Depass_Period = 60; //every 7 days for depass event
unsigned long int Depass_Duration = 10 ; // depass for 120 seconds
unsigned long int Depass_ON = 0 ;
unsigned long int Depass_Counter = 0;
unsigned long int Sample_Counter = 0;
unsigned long int WriteTX_Counter = 0;
unsigned long int count = 0;
unsigned char input;
char data = 1;

void SkipLine(void){
    printf("\n");
    printf("\r");
}

void main() {
    INTCON = 0;                 // disable interrupts.
    ANSELA = 0x00;              // all digital IO
    ANSELB = 0x00;              // all digital IO
    TRISA = 0b00000000;         // Configure PORTA as output 
    PORTA = 0b00000111;         // Initialize PORTA, all load relays are off.
    ADCON0 = 7;                 // disables ADC
    CM1CON0 = 7;                // Disable analog comparators
    TRISB = 0b10111001;         // all outputs bar RB1/RX pin, and RB7 (Prog'd)

    init_comms();

    printf("\n");
    printf("\r");
    printf("*******************************");
    printf("\n");
    printf("\r");
    printf("*METROL RELAY CONTROLLER MK1.0*");
    printf("\n");
    printf("\r");
    printf("*******************************");
    printf("\n");
    printf("\r");

    printf("Default timings are :");
    printf("\n");
    printf("\r");
    printf("Sample Period = ");
    printf("%d seconds", Sample_Period);
    printf("\n");
    printf("\r");

    printf("\n");
    printf("\r");
    printf("Sample Duration = ");
    printf("%d seconds", Sample_Duration);
    printf("\n");
    printf("\r");

    printf("\n");
    printf("\r");
    printf("WriteTX Period = ");
    printf("%d seconds", WriteTX_Period);
    printf("\n");
    printf("\r");

    printf("\n");
    printf("\r");
    printf("WriteTX Duration = ");
    printf("%d seconds", WriteTX_Duration);
    SkipLine;

    printf("\n");
    printf("\r");
    printf("Depassivation Period (Days)= ");
    printf("%d Days", Depass_Period);
    printf("\n");
    printf("\r");
    printf("\n");
    printf("\r");
    printf("Depassivation Duration  = ");
    printf("%d seconds", Depass_Duration);
    printf("\n");
    printf("\r");

    if (RB7 == 1)
    {
        printf("requires set up");

        printf("\n");
        printf("\r");
        printf("\n");
        printf("\r");

        printf("Enter value for Sample Period in minutes <0-255> ");
        printf("\n");
        printf("\r");

        char str[50];

        printf("Enter a string : ");
        gets(str);

        printf("You entered: %s", str);
        int SamplePeriodVal;
        SamplePeriodVal = atoi(str);
        printf("Sample Period Value entered = %d\n", SamplePeriodVal);
    }

    printf("\n");
    printf("\r");
    printf("system already configured");
    printf("\n");
    printf("\r");

    unsigned int Sample_Period_Units;
    Sample_Period_Units = EEPROM_READ(0x00);
    printf("sample value held in first eeprom address 0x00 is %d", EEPROM_READ(0x00));

    printf("\n");
    printf("\r");
    printf("load profile starting.....");
    printf("\n");
    printf("\r");

    while (1) {
        printf("\n");
        printf("\r");
        printf("test!");
        printf("\n");
        printf("\r");

        __delay_ms(990);

        if (Sample_Counter >= Sample_Period){
            PORTA = 0b00000110; //set Sample relay ON

            Sample_ON++;

            if (Sample_ON > Sample_Duration){
                Sample_ON = 0;
                Sample_Counter = 0;
                PORTA = 0b00000111;

            }
        }

        if (WriteTX_Counter >= WriteTX_Period){
            PORTA = 0b00000100; //set Write relay ON

            WriteTX_ON++;

            if (WriteTX_ON > WriteTX_Duration){
                WriteTX_ON = 0;
                WriteTX_Counter = 0;
                PORTA = 0b00000111;

            }
        }

        if (Depass_Counter >= Depass_Period){
            PORTA = 0b00000011; //set Depass relay ON


            Depass_ON++;

            if (Depass_ON > Depass_Duration){
                Depass_ON = 0;
                Depass_Counter = 0;
                PORTA = 0b00000111;

            }
        }

        Sample_Counter++;
        WriteTX_Counter++;
        Depass_Counter++;
        count++;            // increment total count for system

        printf("\n");
        printf("\r");

        int SampleAct;
        SampleAct = RB3;
        printf("Port B sample value =%d  ", SampleAct);

        printf("\r");
        printf("\n");

        int WriteTXAct;
        WriteTXAct = RB4;
        printf("Port B WriteTX value =%d  ", WriteTXAct);

        printf("\r");
        printf("\n");

        int DepassAct;
        DepassAct = RB5;
        printf("Port B Depass value =%d  ", DepassAct);

        printf("\r");
        printf("\n");
        printf("%ld", count);

        int PortB_Val;

        PortB_Val = PORTB & 0b00111000;

        switch (PortB_Val)
        {

        case 0x28:
            RB6 = RB6;
            printf("\n");
            printf("\r");
            printf("Sample+Depass error");
            break;

        case 0x30:
            RB6 = RB6;
            printf("\n");
            printf("\r");
            printf("Write+Depass error");
            break;

        case 0x38:
            RB6 = RB6;
            printf("\n");
            printf("\r");
            printf("Write+Sample+Depass error");
            break;

        default:
            RB6 = !RB6;
        }
    }
}

Answer 1

你的代码只依赖于周期性的计时器节拍，所以一般的想法是这样做：

volatile static uint8_t tick;

ISR(TIMER_vec) /* whatever int vector is triggered by your timer */
{
    ++tick;
}


int main () {
    /* [...] */

    while (1)
    {
        uint8_t lasttick = 0;
        while (tick != lasttick)
        {
            lasttick = tick; /* or ++lasttick; for handling "missed" interrupts late */

            /*
             * do your periodic stuff here
             */
        }
        /* wait for next interrupt, e.g. by entering sleep state
           for AVR: */
        sleep_cpu();
    }
}

当然，你必须根据你的芯片来安排你的定时器中断。如果事情变得更加复杂，您可能会对使用ISR填充事件队列的some code I wrote感兴趣。

Answer 2

我可以想象，delay_ms()的精度完全由XTAL的稳定性决定--这不太可能是你的问题，除非你在一个低精度的RC振荡器上运行，如果是这样的话，使用计时器硬件或ISR将不会有帮助，因为它们都运行在相同的时钟上。

您的问题在于您的设计和printf()的使用。如果printf()未缓冲，或者您正在填充缓冲区，则循环时间将由调试输出主导-如果printf()输出通过UART串行端口，则循环时间将由该通道的波特率和文本输出量决定。

基本的问题是你的循环时间是延迟加上执行循环体的时间的总和-这可能是可变的和不确定的，这取决于printf的实现，输出设备，它的数据速率以及是否有流控制。

一种更好的方法是轮询计时器，并在到时间时执行循环体，而不是在固定的延迟之后执行。定时器的实现是特定于平台的，但是假设您实现了一个定时器，其ISR每毫秒递增一个计数器，并且计数器由函数gettime_ms()读取，那么您的循环将变成：

int start_1000 = gettime_ms() ;
int now = start ;
for(;;)
{
    now = gettime_ms() ;

    if( now - start_1000 >= 1000 )
    {
        start_1000 += 1000 ;

        //  Loop body here - will execute every 1000ms
        // so long as the loop body takes less than 1000ms in total.
        ...
    }
}

然后，您可以轻松地以不同的速率引入其他周期操作：

int now = gettime_ms() ;
int start_1000 = now;
int start_50 = now ;

for(;;)
{
    now = gettime_ms() ;

    // Every second
    if( now - start_1000 >= 1000 )
    {
        start_1000 += 1000 ;

        // 1 second operations here
        ...
    }

    // Every 50ms
    if( now - start_50 >= 50)
    {
        start_50 += 50 ;

        // 50ms operations here 
        ...
    }
}

您还可以在周期块之外快速执行后台任务，以便最大限度地利用可用的CPU时间。例如，这样的任务可能包括安全监控-可能不是你想要等待一整秒的事情。

最终，如果有大量的时间关键型任务和事件处理要执行，那么RTOS可能是合适的。