Trouble setting up interrupts in a header file

duwaar0 · July 19, 2022, 8:13pm

Here's my code:

color_sensor.ino

#include "TCS3200.h"

void setup() {
    TCS3200_begin();
    Serial.begin(9600);
}

void loop() {
    delay(200);
    Serial.print(frequencyRead());
    Serial.print("kHz");
    Serial.println();
}

TCS3200.h

#ifndef _TCS3200
#define _TCS3200

// PINS
uint8_t
    OUT = 2,
    OE = 3,
    S0 = 4,
    S1 = 5,
    S2 = 6,
    S3 = 7;

// PULSE COUNTING
volatile uint16_t
    pulse_count;
uint32_t
    start_time,
    end_time;

void TCS3200_begin() {
    pinMode(OE, OUTPUT);
    pinMode(S0, OUTPUT);
    pinMode(S1, OUTPUT);
    pinMode(S2, OUTPUT);
    pinMode(S3, OUTPUT);
    
    digitalWrite(OE, LOW);
    
    digitalWrite(S0, HIGH);
    digitalWrite(S1, LOW);
    
    digitalWrite(S2, HIGH);
    digitalWrite(S3, LOW);
}

void ISR_pulseIncrement() {
    pulse_count += 1;
}
attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);

float frequencyRead() {
    // Returns frequency in kHz
    end_time = micros();
    float frequency = 1000.0 * pulse_count / (end_time - start_time);
    start_time = micros();  
    pulse_count = 0;
    return frequency;
}

#endif // _TCS3200

And the error I'm getting is this:

TCS3200.h:39:16: error: expected constructor, destructor, or type conversion before '(' token
attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);
^
exit status 1
expected constructor, destructor, or type conversion before '(' token

It seems like the IDE wants me to put the attachInterrupt() inside of a function, but when I do that, the ISR is out of scope, so I'm not sure what to do.

PieterP · July 19, 2022, 8:19pm

You shouldn't define variables in header files.

You cannot have statements like this outside of a function.

Declare the ISR before you use it:

void ISR_pulseIncrement();

b707 · July 19, 2022, 8:40pm

this is not true.
This can be done if the header is included in only one translation unit

PieterP · July 19, 2022, 8:49pm

But then it shouldn't be a header file. Just because you can use it without errors in some cases doesn't mean you should.

If you want the nuanced guideline, you usually shouldn't define non-const, non-inline variables in header files.
C++ Core Guidelines: SF.2: A .h file must not contain object definitions or non-inline function definitions

westfw · July 19, 2022, 8:58pm

You shouldn't define functions in a header file, either.

duwaar0 · July 20, 2022, 7:33pm

Coming from Python, my understanding of header files is that they can be used to refactor code so that the main file stays more neat. If this was Python, I would make all those functions and data into members of a class. Then, I would use that class to interact with the sensor hardware. I thought I might do this with a struct, but all the sources I read said that that was misguided and not what structs are for.

If there is a better way to structure this code, links to sources where I can learn more would be helpful. I'm trying to refactor in preparation for adding some more functionality.

At any rate, I appreciate all the suggestions for best practices, but none of them seem to answer my question. I want to understand why I'm getting the error I'm getting and how I can fix it. Why am I getting this error, and how can I fix it?

gfvalvo · July 20, 2022, 7:38pm

You were already told why:

To fix it, put all executable code inside of a function.

gfvalvo · July 20, 2022, 7:44pm

See my Reply #5 in this Thread for some basic guidelines for multi-file projects.

duwaar0 · July 20, 2022, 7:45pm

In my initial post, I specifically addressed this suggestion. I tried putting this code into a function, but then I get a new error because the ISR function is out of scope. I tried defining the ISR function within the function in which I called attachInterrupt(), but then I get a third error, because it is not allowed to define a function within a function.

b707 · July 20, 2022, 7:51pm

it is common practice to put the attachinterrupt() line within setup() in your main .ino file

gfvalvo · July 20, 2022, 7:53pm

Too bad you didn't post the code for that attempt ....

duwaar0 · July 20, 2022, 7:54pm

I did that at first, but now that I'm refactoring my code, I don't want to put the interrupt definition right in the main .ino file. That's why I tried putting it in a .h file.

b707 · July 20, 2022, 7:55pm

@duwaar0
I am agree with post #11

duwaar0 · July 20, 2022, 8:11pm

Here is what my code looks like when I put the attachInterrupt() function inside of another function:

color_sensor.ino

#include "TCS3200.h"

void setup() {
    TCS3200_begin();
    Serial.begin(9600);
}

void loop() {
    delay(200);
    Serial.print(frequencyRead());
    Serial.print("kHz");
    Serial.println();
}

TCS3200.h

#ifndef _TCS3200
#define _TCS3200

// PINS
uint8_t
    OUT = 2,
    OE = 3,
    S0 = 4,
    S1 = 5,
    S2 = 6,
    S3 = 7;

// PULSE COUNTING
volatile uint16_t
    pulse_count;
uint32_t
    start_time,
    end_time;

void TCS3200_begin() {
    pinMode(OE, OUTPUT);
    pinMode(S0, OUTPUT);
    pinMode(S1, OUTPUT);
    pinMode(S2, OUTPUT);
    pinMode(S3, OUTPUT);
    
    digitalWrite(OE, LOW);
    
    digitalWrite(S0, HIGH);
    digitalWrite(S1, LOW);
    
    digitalWrite(S2, HIGH);
    digitalWrite(S3, LOW);
    
    attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);
}

void ISR_pulseIncrement() {
    pulse_count += 1;
}

float frequencyRead() {
    // Returns frequency in kHz
    end_time = micros();
    float frequency = 1000.0 * pulse_count / (end_time - start_time);
    start_time = micros();  
    pulse_count = 0;
    return frequency;
}

#endif // _TCS3200

Error message:

TCS3200.h:35:49: error: 'ISR_pulseIncrement' was not declared in this scope
attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);
^~~~~~~~~~~~~~~~~~
exit status 1
'ISR_pulseIncrement' was not declared in this scope

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Here is what the code looks like when I put the ISR function definition in side the same function as the attachInterrupt() function call in an attempt to have them both in the same scope:

color_sensor.ino

#include "TCS3200.h"

void setup() {
    TCS3200_begin();
    Serial.begin(9600);
}

void loop() {
    delay(200);
    Serial.print(frequencyRead());
    Serial.print("kHz");
    Serial.println();
}

TCS3200.h

#ifndef _TCS3200
#define _TCS3200

// PINS
uint8_t
    OUT = 2,
    OE = 3,
    S0 = 4,
    S1 = 5,
    S2 = 6,
    S3 = 7;

// PULSE COUNTING
volatile uint16_t
    pulse_count;
uint32_t
    start_time,
    end_time;

void TCS3200_begin() {
    pinMode(OE, OUTPUT);
    pinMode(S0, OUTPUT);
    pinMode(S1, OUTPUT);
    pinMode(S2, OUTPUT);
    pinMode(S3, OUTPUT);
    
    digitalWrite(OE, LOW);
    
    digitalWrite(S0, HIGH);
    digitalWrite(S1, LOW);
    
    digitalWrite(S2, HIGH);
    digitalWrite(S3, LOW);
    
    void ISR_pulseIncrement() {
    pulse_count += 1;
    }

    attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);
}

float frequencyRead() {
    // Returns frequency in kHz
    end_time = micros();
    float frequency = 1000.0 * pulse_count / (end_time - start_time);
    start_time = micros();  
    pulse_count = 0;
    return frequency;
}

#endif // _TCS3200

Error message:

TCS3200.h:35:31: error: a function-definition is not allowed here before '{' token
void ISR_pulseIncrement() {
^
TCS3200.h:39:49: error: 'ISR_pulseIncrement' was not declared in this scope
attachInterrupt(digitalPinToInterrupt(OUT), ISR_pulseIncrement, RISING);
^~~~~~~~~~~~~~~~~~
exit status 1
a function-definition is not allowed here before '{' token

Is that helpful? Sorry about the formatting of the error message. I couldn't figure out how to get the "^" characters in the right place, but hopefully that's enough information.

gfvalvo · July 20, 2022, 8:21pm

The problem with this attempt may be due to lack of a function prototype. The Arduino auto-prototype generator may be failing because of the way you're trying to #include excusable code in a .h file.

As you already noted, a function definition is not allowed inside of another function.

Actually, all three of your attempts are fundamentally misguided. See:

b707 · July 20, 2022, 8:22pm

In the first code try to move

ISR_pulseIncrement()

function above the

TCS3200_begin()

one

But in general I agree with @gfvalvo

westfw · July 21, 2022, 2:23am

Also, in C, you can't define a function (ISR_pulseincrement) inside of another function (TCS3200_begin) - the definition needs to be at global scope, but the USE has to be inside another function.

system · January 17, 2023, 2:24am

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