Hey, i'm currently working on a project to control a LED-strip (NEOPIXEL) with a rotary-switch (with push-button function).
To adress the LEDs i've includet FastLED.h, to encode the rotary, i includet the library Encoder.h.
Everything works almost well apart from the push-button, but thats a problem for an other thread!
Now i tried to optimize my sketch to (re-)set the "NUM_LEDS" only by "serial.input()" in "void setup()", but i only get a miss match of LED-adressing.
I know the problem is that i try to redefine the global constant in the setup()-function and this causes the failure, but i dont know why! I'm very new in arduino Cc-programming and not very firm with it.
In my code i set NUM_LEDS as global with
#include <FastLED.h> // use LED-library to adress the used LED-strip correctly
const byte NUM_LEDS = 75; // similar to #define NUM_LEDS 75
CRGB leds[NUM_LEDS]; // LED color-schema
and everything is fine.
Next, i re-defined NUM_LEDS in void setup() (at this point without serial-input read, its not necessary for testing)
#include <FastLED.h> // use LED-library to adress the used LED-strip correctly
const byte NUM_LEDS = 75; // similar to #define NUM_LEDS 75
CRGB leds[NUM_LEDS]; // LED color-schema
...
...
void setup() {
#ifdef NUM_LEDS
#undef NUM_LEDS
#endif#define NUM_LEDS 75
...
...
}
...
But with this config, the LED-adressing is miss matched. All LEDs light up and do anything else than it should do.
How can i reset / redefine NUM_LEDS in a correct way? I need the redefinition because i want to change the amount of LEDs dynamic and tell the amount at arduino startup.
Maybe, is there a way the to read serial input before the NUM_LEDS has to be defined and setup() get initialised ?
Attached the whole sketch
Thanks for every help.
Any other code-optimizations are welcome too 
LED_rotary_Control.ino (9.19 KB)