将ino sketch 转换为C++ 类，非静态成员函数的使用无效

Question

我正在尝试将编译好的 .ino 草图转换为 C++ 类，工作代码是：

byte statusLed    = 13;
byte sensorInterrupt = 0;  // 0 = digital pin 2
byte sensorPin       = 2;

// The hall-effect flow sensor outputs approximately 4.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 4.5;

volatile byte pulseCount;  

float flowRate;
unsigned int flowMilliLitres;
unsigned long totalMilliLitres;

unsigned long oldTime;

void setup()
{

  // Initialize a serial connection for reporting values to the host
  Serial.begin(38400);

  // Set up the status LED line as an output
  pinMode(statusLed, OUTPUT);
  digitalWrite(statusLed, HIGH);  // We have an active-low LED attached

  pinMode(sensorPin, INPUT);
  digitalWrite(sensorPin, HIGH);

  pulseCount        = 0;
  flowRate          = 0.0;
  flowMilliLitres   = 0;
  totalMilliLitres  = 0;
  oldTime           = 0;

  // The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
  // Configured to trigger on a FALLING state change (transition from HIGH
  // state to LOW state)
  attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}

/**
 * Main program loop
 */
void loop()
{

   if((millis() - oldTime) > 1000)    // Only process counters once per second
  { 
    // Disable the interrupt while calculating flow rate and sending the value to
    // the host
    detachInterrupt(sensorInterrupt);

    // Because this loop may not complete in exactly 1 second intervals we calculate
    // the number of milliseconds that have passed since the last execution and use
    // that to scale the output. We also apply the calibrationFactor to scale the output
    // based on the number of pulses per second per units of measure (litres/minute in
    // this case) coming from the sensor.
    flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;

    // Note the time this processing pass was executed. Note that because we've
    // disabled interrupts the millis() function won't actually be incrementing right
    // at this point, but it will still return the value it was set to just before
    // interrupts went away.
    oldTime = millis();

    // Divide the flow rate in litres/minute by 60 to determine how many litres have
    // passed through the sensor in this 1 second interval, then multiply by 1000 to
    // convert to millilitres.
    flowMilliLitres = (flowRate / 60) * 1000;

    // Add the millilitres passed in this second to the cumulative total
    totalMilliLitres += flowMilliLitres;

    unsigned int frac;

    // Print the flow rate for this second in litres / minute
    Serial.print("Flow rate: ");
    Serial.print(int(flowRate));  // Print the integer part of the variable
    Serial.print(".");             // Print the decimal point
    // Determine the fractional part. The 10 multiplier gives us 1 decimal place.
    frac = (flowRate - int(flowRate)) * 10;
    Serial.print(frac, DEC) ;      // Print the fractional part of the variable
    Serial.print("L/min");
    // Print the number of litres flowed in this second
    Serial.print("  Current Liquid Flowing: ");             // Output separator
    Serial.print(flowMilliLitres);
    Serial.print("mL/Sec");

    // Print the cumulative total of litres flowed since starting
    Serial.print("  Output Liquid Quantity: ");             // Output separator
    Serial.print(totalMilliLitres);
    Serial.println("mL"); 

    // Reset the pulse counter so we can start incrementing again
    pulseCount = 0;

    // Enable the interrupt again now that we've finished sending output
    attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
  }
}

/*
Insterrupt Service Routine
 */
void pulseCounter()
{
  // Increment the pulse counter
  pulseCount++;
}

我的转换尝试如下：

.H 文件：

class FlowSensor
{
public:
    FlowSensor(int pin);
    void begin();
    void run();
private:
    int _pin;
    byte sensorInterrupt = 0;  // 0 = digital pin 2

    // The hall-effect flow sensor outputs approximately 4.5 pulses per second per
    // litre/minute of flow.
    float calibrationFactor = 4.5;

    float flowRate;

    unsigned int flowMilliLitres;
    unsigned long totalMilliLitres;

    unsigned long oldTime;
    volatile unsigned long pulseCount;
    //volatile byte pulseCount;
    void pulseCounter();
};

和 C 文件：

FlowSensor::FlowSensor(int pin)
{
    _pin = pin;
}

void FlowSensor::begin()
{
    pinMode(_pin, INPUT);
    digitalWrite(_pin, HIGH);

    pulseCount = 0;
    flowRate = 0.0;
    flowMilliLitres = 0;
    totalMilliLitres = 0;
    oldTime = 0;

    sensorInterrupt = digitalPinToInterrupt(_pin);

    // The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
    // Configured to trigger on a FALLING state change (transition from HIGH
    // state to LOW state)
    attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}

void FlowSensor::run()
{
    if ((millis() - oldTime) > 1000)    // Only process counters once per second
    {
        // Disable the interrupt while calculating flow rate and sending the value to
        // the host
        detachInterrupt(sensorInterrupt);

        // Because this loop may not complete in exactly 1 second intervals we calculate
        // the number of milliseconds that have passed since the last execution and use
        // that to scale the output. We also apply the calibrationFactor to scale the output
        // based on the number of pulses per second per units of measure (litres/minute in
        // this case) coming from the sensor.
        flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;

        // Note the time this processing pass was executed. Note that because we've
        // disabled interrupts the millis() function won't actually be incrementing right
        // at this point, but it will still return the value it was set to just before
        // interrupts went away.
        oldTime = millis();

        // Divide the flow rate in litres/minute by 60 to determine how many litres have
        // passed through the sensor in this 1 second interval, then multiply by 1000 to
        // convert to millilitres.
        flowMilliLitres = (flowRate / 60) * 1000;

        // Add the millilitres passed in this second to the cumulative total
        totalMilliLitres += flowMilliLitres;

        unsigned int frac;

        // Print the flow rate for this second in litres / minute
        Serial.print("Flow rate: ");
        Serial.print(int(flowRate));  // Print the integer part of the variable
        Serial.print(".");             // Print the decimal point
        // Determine the fractional part. The 10 multiplier gives us 1 decimal place.
        frac = (flowRate - int(flowRate)) * 10;
        Serial.print(frac, DEC);    // Print the fractional part of the variable
        Serial.print("L/min");
        // Print the number of litres flowed in this second
        Serial.print("  Current Liquid Flowing: ");          // Output separator
        Serial.print(flowMilliLitres);
        Serial.print("mL/Sec");

        // Print the cumulative total of litres flowed since starting
        Serial.print("  Output Liquid Quantity: ");          // Output separator
        Serial.print(totalMilliLitres);
        Serial.println("mL");

        // Reset the pulse counter so we can start incrementing again
        pulseCount = 0;

        // Enable the interrupt again now that we've finished sending output
        attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
    }
}

/*
 * Interrupt Service Routine
 */
void FlowSensor::pulseCounter()
{
  // Increment the pulse counter
    pulseCount++;
}

我得到的错误是：

C:\Users\marcp\Dropbox\Arduino\FlowSensor\FlowSensor.cpp: In member function 'void FlowSensor::begin()':
C:\Users\marcp\Dropbox\Arduino\FlowSensor\FlowSensor.cpp:24:56: error: invalid use of non-static member function
  attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
                                                        ^
C:\Users\marcp\Dropbox\Arduino\FlowSensor\FlowSensor.cpp: In member function 'void FlowSensor::run()':
C:\Users\marcp\Dropbox\Arduino\FlowSensor\FlowSensor.cpp:80:57: error: invalid use of non-static member function
   attachInterrupt(sensorInterrupt, pulseCounter, FALLING);

应该标记为静态？

Answer 1

ISR 必须不返回任何内容并且不接受任何参数。 这就是 ISR 的规则。 这只是规则，我认为你不能改变。 成员函数都有伴随它们的不可见的“this”。

想想看，如果你有这个类的多个实例，中断应该从哪个实例调用？ 它不知道，这就是您不能将成员函数用作 ISR 的原因。

您可以创建一个静态方法（以便所有实例共享）并将静态方法用作 ISR，但它无法访问任何成员变量。 或者你可以在你的草图中编写一个 ISR，从类的正确实例调用正确的方法。

但是您根本不能将成员函数用作 ISR。 这只是违反规则。

Answer 2

将类外的 attachInterrupt() 语句连同其处理程序一起移动到主 .ino 文件中。