Customizable LED_BUILTIN

[marshfolx]

I build a mega128 board and want to put LED_BUILTIN on D16 / PG3 rather than D13 / PB5 which is a PWM channel of Timer1. I think it is better to put a #ifndef around the #define LED_BUILTIN in 64-pin-avr/pins_arduino.h, so that I can use build flag to define my assignment.

// Builtin LED
#ifndef LED_BUILTIN
#define LED_BUILTIN   (13)
#endif
static const uint8_t LED = LED_BUILTIN;

[MCUdude]

LED_BUILTIN is just a constant, and isn't "tied" to a specific pin at all. You don't have to use the constant if you don't want to. However, you should be able to deal with it in your code like so:

#ifdef LED_BUILTIN
#undef LED_BUILTIN
#define LED_BUILTIN PIN_PG3
#endif

[marshfolx]

@MCUdude Some libraries and example code use LED_BUILTIN to show simple notifications, I have to directly change the source code if i can't use build flag. Or I must place #undef LED_BUILTIN before including the library.

[MCUdude]

You can't override pre-defined macros in the sketch, and expect the compiler to pick it up and re-compile the libraries.

This means that the only viable way to override the LED_BUILTIN macro would either to add -DLED_BUILTIN=13 as a compiler build flag (difficult with Arduino IDE, possible with PlatformIO), or modify the source code in the MCUdude_corefiles folder. I'm happy to add your suggestion to the code base (only defined LED_BUILTIN if not already defined), but it won't solve your issue. The compiler would still not pick this up as long as the macro is overridden in the sketch.

[marshfolx]

Thanks for that, and of course I'm using PlatformIO. I realized that #undef can't affect library code just after I sent the comment. No problem about it.