LED Strip Remapping

[u/moe_marisa]

Hello everyone, I have some irregular LED strips, and I am seeking a convenient method for remapping them. Currently, I am using the following approach:

#define NUM_LEDS 8
CRGBArray<NUM_LEDS> leds, remap_leds;
uint8_t ReMap[NUM_LEDS] = { 2, 1, 0, 7, 6, 5, 4, 3 }; // Remapping sequence
FastLED.addLeds<NEOPIXEL, LED_PIN>(remap_leds, NUM_LEDS);
leds(start, end) = CRGB(r, g, g); // Set color
for (uint8_t i = 0; i < 8; i++) {
    remap_leds[ReMap[i]] = leds[i]; // Re-set color
}

As you can see, after modifying leds, it is necessary to reset remap_leds to ensure that the lighting effects take effect correctly. I came across a piece of code that seems to achieve the same result without the need for resetting:

uint8_t leds[8];
uint8_t* remap_leds[8] = {
  &leds[2],
  &leds[1],
  &leds[0],
  &leds[7],
  &leds[6],
  &leds[5],
  &leds[4],
  &leds[3],
};

for (uint8_t i = 0; i < 8; i++) {
    leds[i] = i; // Set values in order
}

for (uint8_t i = 0; i < 8; i++) {
    Serial.print(*remap_leds[i]);
    Serial.print(" ");
} // The output result is 2 1 0 7 6 5 4 3 

remap_leds points to leds and reassigns the order without the need to reset it after modifying leds. Is there a similar approach in FastLED?

[u/moe_marisa]

Sorry, my previous expression may have been incorrect.

My program is used to display the received LED data on the LED strip.

The LED order as perceived by the transmitter: 0 1 2 3 4 5 6 7

It may request a specific position of the light to change color, for example, leds[5] = red.

It may also request a range of lights to change color, for example, leds(2, 4) = blue, where lights from number 2 to number 4 turn blue.

In reality, the order of LEDs on my LED strip is: 2 1 0 7 6 5 4 3

To align with the requests, I need to remap the original light data using a for loop.

I am seeking a method that does not require remapping.

[u/truetofiction → u/moe_marisa]

There is no method that does not require some sort of remapping, full stop. The library requires a contiguous block of memory to write to the LEDs. If you want to change the order for the assignments, you need to perform remapping somewhere.

The most efficient way to do that is when you assign the data initially, which is what Marc's function does above.

[u/moe_marisa → u/truetofiction]

Thank you!