Catching instantiation errors

Projects Programming
1

Referring to this WOKWI project:

Starting at line 87 are these statements:

const uint8_t orangeLED = 4;
const uint8_t greenLED = 2;
const uint8_t blueLED = 4;
const uint8_t yellowLED = 7;
const uint8_t orangeSwitch = A0;
const uint8_t greenSwitch = A1;
const uint8_t blueSwitch = A2;
const uint8_t yellowPot = A3;

// Following the form: input inverted, output pin, output inverted, T1 ms, T2 ms.
// T2 is optional; if T2 not included ON and OFF times will be equal.
//
SimpleFlasher orangeFlasher(false, orangeLED, false, 337, 2107); // Instantiate a flasher object
SimpleFlasher greenFlasher(true, greenLED, false, 100, 3000); // Instantiate a flasher object
SimpleFlasher blueFlasher(false, blueLED, false, 647); // Instantiate a flasher object
SimpleFlasher yellowFlasher(true, yellowLED, false, 200, 2100); // Instantiate a flasher object

Notice that the orangeLED and the blueLED are both given the same pin number.  Unsurprisingly this causes the respective outputs to misbehave.

My question:  Is there a way to crosscheck the pin assignments against each other and flag duplicates to give some notice at run time?

2

Why at runtime? Compile time would be better but neither are really possible.

That is why I always have a pin declaration section with the pins in ascending order, not grouped by function or category.

1 Like
3

I can see a way to do it at compile-time if the constant identifiers (e.g. use 4 instead of orangeLED) are not used. But that would place an annoying restriction on the user.

I think the only way to do it at run-time would be to maintain a global integer set. That's not especially difficult but more code means more possibility of bugs.

The biggest caveat with run-time detection would be deciding how to report the mistake. Dealing with it during construction is certainly problematic.

4

Now that I think of it all I was really after was some way to let a human know there's a problem before the hardware starts breaking.   So compile time would work too.

5

At a minimum I suppose one could flash the built-in LED on an UNO.  But, what if the built-in LED is one of those designated for a flasher?  Possibly a message could be sent to the serial monitor.

I think a comment to the effect of 'Don't do this!' may be the answer.

6

That would be even more obvious if you assigned names in pin-number order:

const uint8_t greenLED = 2;
const uint8_t orangeLED = 4;
const uint8_t blueLED = 4;
const uint8_t yellowLED = 7;

That makes it a little clearer that you are assigning two different names to Pin 4.

7

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