Shareef Jalloq

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5 years, 9 months ago.

How to check a pin supports required capture functionality?

Hi,

I'm writing a class that uses the capture functionality of the timer block. Different devices have certain fixed location pins that support capture functionality. If I want to allow the user of the class to select which pin they want to use, how can I check that they've selected a pin that actually has the capture functionality?

Thanks.

1 Answer

Zoltan Hudak
5 years, 8 months ago.

Hello, Shareef

There are probably many ways how to do it. You can for example let the compiler check/enforce it by declaring an enum type and class as follows:

MyClass.h

#define "mbed.h"

typedef enum {
#if defined(TARGET_LPC1768)    
    capturePin1 = p9,
    capturePin2 = p10,
#elif defined(TARGET_STM)
    capturePin1 = PA_3,
    capturePin2 = PA_4,
    capturePin3 = PB_10,
    capturePin4 = PC_4,
#endif
} CapturePin;

class MyClass : public InterruptIn
{
public:
    MyClass(CapturePin pin) : InterruptIn((PinName)pin)
    {
        
    }    
};

The user will be then forced to use only the designed pins:

main.cpp

#include "mbed.h"
#include "MyClass.h"

//MyClass myClass(p9);           // reports compile time error
MyClass myClass(capturePin3);  // compiles fine for STM boards but reports compile time error for LCP1768

int main()
{
    //..

Accepted Answer