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I’m trying to get a WS2815 LED strip working with an Arduino Nano ESP32, but I can’t get it to light up. The strange thing is that with an Arduino UNO, using the exact same circuit and sketch, everything works perfectly.

Here’s my setup:

  • The WS2815 LED strip is powered by 12 V. I’m using a DC-DC converter to step down to 5 V, which powers both the Arduino Nano ESP32 and a SN74AHCT125N buffer.

  • The data signal goes from pin 2 of the Arduino through the buffer (to shift from 3.3 V to 5 V) and then to the D pin of the WS2815 strip.

  • All GNDs (Arduino, DC-DC converter, LED strip, and buffer) are connected together. I’m using the FastLED library.

  • I tested the buffer: when I apply a fixed 3.3 V input, I get 5 V output, so the level shifting seems to be working correctly.

The problem is that when I upload the sketch to the Nano ESP32, the LEDs stay completely off. With the Arduino UNO, the exact same code and wiring work perfectly.

I also noticed that during the compilation and upload process in the Arduino IDE, it shows “Done uploading”, but I suspect the code might not be running correctly on the ESP32, or the compilation may not be fully compatible.

What is causing the problem?

    #include <FastLED.h>
    
    #define NUM_LEDS 79
    #define DATA_PIN 2
    
    CRGB leds[NUM_LEDS];
    
    void setup() {
      FastLED.addLeds<WS2815, DATA_PIN, GRB>(leds, NUM_LEDS);
      FastLED.setBrightness(180);
    }
    
    void loop() {
      fill_solid(leds, NUM_LEDS, CRGB::Red);
      FastLED.show();
      delay(1000);
    
      fill_solid(leds, NUM_LEDS, CRGB::Blue);
      FastLED.show();
      delay(1000);
    
      fill_solid(leds, NUM_LEDS, CRGB::Green);
      FastLED.show();
      delay(1000);
    }

IDE Screenshot IDE Screenshot

Arduino Nano ESP32 Circuit Arduino Nano ESP32 Circuit

Arduino UNO Circuit Arduino UNO Circuit

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  • I wanted to update this thread and thank everyone who offered suggestions. I finally found the solution! Thanks again for all the help! I'm posting this solution here in case anyone else runs into this same frustrating problem. Commented Nov 13 at 11:46
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    please do not post a picture of text unless absolutely necessary ... copy and paste the IDE output ... format as code for readability Commented Nov 13 at 17:32
  • OK. What was the solution? Commented Nov 13 at 18:09
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    please write an answer below ... the solution does not belong in the question body Commented Nov 14 at 15:42
  • I solved the issue with the Arduino Nano ESP32. It wasn't the wiring, but a pin mapping problem in the Arduino IDE. The fix involved two steps: IDE: Change the setting in Tools > Pin Numbering to "By GPIO number (legacy)". (The default "By Arduino pin" was the issue). Code: Update the pin definition to use the GPIO name (e.g., change #define DATA_PIN 2 to #define DATA_PIN D2). After these changes, the LED strip worked. It seems libraries like FastLED require this "legacy" numbering on the ESP32. Commented Nov 14 at 20:31

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Since the OP hasnt posted the answer and Question closure may occur, I am copying it over.

I solved the issue with the Arduino Nano ESP32. It wasn't the wiring, but a pin mapping problem in the Arduino IDE. The fix involved two steps:

  1. IDE: Change the setting in Tools > Pin Numbering to "By GPIO number (legacy)". (The default "By Arduino pin" was the issue).
  2. Code: Update the pin definition to use the GPIO name (e.g., change #define DATA_PIN 2 to #define DATA_PIN D2).

After these changes, the LED strip worked. It seems libraries like FastLED require this "legacy" numbering on the ESP32.

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