ISR + 代码，将计数代码与 ISR 例程集成

Question

我有一段用于 PIC 设备的 C 代码，它将 4 个单独的继电器驱动为预定义的模式，每个继电器都通过计数时间和发生频率来单独设置。这种模式无限期地继续下去，但发现标准 delay_ms 上的时间不够准确。我希望将其转换为 ISR 例程，我附上了下面的代码，它依赖于标准延迟供您阅读，我主要关心的是如何将此代码抽象为 ISR，因为我知道不要将所有这些代码粘贴到实际的 ISR 例程中，任何非常感谢您的建议。

__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

您的代码仅依赖于周期性计时器滴答声，因此一般的想法是执行以下操作：

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

我想 delay_ms() 的精度完全取决于您的 XTAL 的稳定性 - 这不太可能是您的问题，除非您在低精度 RC 振荡器上运行，如果是这种情况，请使用计时器硬件或 ISR 无济于事，因为它们都在同一个时钟上运行。

您的问题在于您的设计和 printf() 的使用。如果 printf() 没有缓冲，或者您正在填充缓冲区，则循环时间将由调试输出控制 - 如果 printf() 输出是通过 UART 串​​行端口，则循环时间将由波特率决定该通道和文本输出量。

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

更好的方法是轮询计时器并在需要执行循环体时执行循环体，而不是在固定延迟之后执行。计时器的实现是特定于平台的，但假设您实现了一个计时器，其 ISR 每毫秒递增一个计数器，并且该计数器由函数 gettime_ms() 读取，那么您的循环变为：

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性操作：

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 
        ...
    }
}

您还可以在周期性块之外执行快速的后台任务工作，以便充分利用可用的 CPU 时间。例如，此类任务可能包括安全监控——这可能不是您想要等待一秒钟的事情。

最终，如果要执行时间紧迫的任务和事件处理，那么 RTOS 可能是合适的。