Question

我有一个用于PIC器件的C代码段，它将4个独立的继电器驱动为预定义的模式，每个继电器通过计算时间和发生频率单独设置。这种模式无限延续，但发现标准delay_ms的时间不够准确。我希望将它转换为ISR例程，我将下面的代码包含在依赖于标准延迟的代码中，我主要关心的是如何将此代码抽象到ISR，因为我知道不要将所有这些代码都粘贴到实际的ISR例程中，任何建议非常感谢。

__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

您的代码仅取决于定期计时器滴答，因此一般的想法是做这样的事情：

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，您必须安排定时器中断，具体取决于您的芯片。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

我认为delay_ms（）的精度完全由XTAL的稳定性决定 - 除非你在低精度RC振荡器上运行，否则这是你的问题，如果是这样的话，那么使用定时器硬件或ISR无济于事，因为它们都在同一个时钟上运行。

你的问题是你的设计和printf（）的使用。如果printf（）是无缓冲的，或者你正在填充缓冲区，那么循环时间将由调试输出控制 - 如果printf（）输出是通过UART串口，则循环时间将由波特率决定。该频道和文字输出量。

基本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 - 这可能是变量和非确定性的，具体取决于printf的实现，输出设备，其数据速率以及是否有流量控制等。

更好的方法是轮询定时器并在有时间而不是在固定延迟之后执行循环体。定时器的实现是特定于平台的，但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后台任务工作，以便充分利用可用的CPU时间。这样的任务可能包括例如安全监控 - 不是你想要等待一整秒的事情。

最终，如果要执行大量时间关键任务和事件处理，那么RTOS可能会有序。

ISR + Code，将计数代码与ISR例程

2 个答案: