# Offset start and end?

**URL:** https://wled.discourse.group/t/offset-start-and-end/388
**Category:** Questions
**Created:** [May 3, 2020, 10:12pm UTC](https://wled.discourse.group/t/offset-start-and-end/388 "2020-05-03T22:12:17Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![pille](https://yyz2.discourse-cdn.com/free1/user_avatar/wled.discourse.group/pille/32/100_2.png) [@pille](https://wled.discourse.group/u/pille)
#### Post date: [May 7, 2020, 2:28pm UTC](https://wled.discourse.group/t/offset-start-and-end/388/2 "2020-05-07T14:28:45Z")

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there’s a feature that adds a hardcoded mapping (see `wled00/FX_fcn.cpp`):

```
//enable custom per-LED mapping. This can allow for better effects on matrices or special displays
//#define WLED_CUSTOM_LED_MAPPING

#ifdef WLED_CUSTOM_LED_MAPPING
//this is just an example (30 LEDs). It will first set all even, then all uneven LEDs.
const uint16_t customMappingTable[] = {
  0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28,
  1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29};

//another example. Switches direction every 5 LEDs.
/*const uint16_t customMappingTable[] = {
  0, 1, 2, 3, 4, 9, 8, 7, 6, 5, 10, 11, 12, 13, 14,
  19, 18, 17, 16, 15, 20, 21, 22, 23, 24, 29, 28, 27, 26, 25};*/

```

you’d need to recompile the firmware after enabling/changing this.

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