ESP32 Forum

Posted: **Wed May 01, 2019 4:32 pm**

Neopixels have great possibilties. With a normal LEDs you can show the state of a system (blue= too cold, red= too hot). With a neopixel you can show values in between with smoothly changing colors from for instance blue ... many colors ... red.

Dimming an LED may be done with PWM - not so with a Neopixel.
And Neopixels have crude timings. (400 ns)

Here is a very small RTOS-task dimming a Neopixel with different colors.
BTW It can be used for very short delays below 1 microsecond.

Have fun

Code: [Select all] [Expand/Collapse]

// ----------- NeoPixel -------------
//---------- WS2812B.pdf ------------
 
inline void BitL(int lp) {
int ii;
  gpio_set_level( RTOS_PinNeo, 0);
  for (ii=0; ii<lp; ii++) {
    asm(" nop");
  }
 
}
 
inline void BitH(int lp) {
int ii;
  gpio_set_level( RTOS_PinNeo, 1);
  for (ii=0; ii<lp; ii++) {
    asm(" nop");
  }
}
 
inline void Bit1() {
  BitH(21);            
  BitL(6); // 21/6      // from experiments
}
 
inline void Bit0() {
  BitH(8);
  BitL(20); // 8/20
}
 
 
inline void Color( uint32_t c) {
int i;
  for (i=0;i<24;i++) {
    if (c & 0x800000 ) Bit1();
    else Bit0();
    c<<=1;
  }
}
 
/**
 * \name NeoPix
 * @{
 * Dimming Blink of NeoPixel, 3 colors: red, green, blue
 *
 * \hideinitializer
 * 
 */
 
void NeoPix( void * pvParameters ) {
uint32_t c=0, cc=0;
int up=1;
unsigned int state=0; 
  gpio_set_direction(RTOS_PinNeo, GPIO_MODE_OUTPUT );  // Data-Pin of NeoPixel
  c=0x01;
  while(1) {
      portDISABLE_INTERRUPTS(); 
      Color(cc); 
      BitL(2);
 
      //SentColors++; // for testing
      // Dimming and blinking ...
      if (up) { c+=1;  if (c>=0xfe)     up=0;}
      else    { c-=1;  if (c==0x000000) { up=1; state+=8;} } // BRG: shift  0, 8, 16
      if (state>16) state=0;
      cc = (c<<state); 
      portENABLE_INTERRUPTS(); 
      vTaskDelay(1);
  }
  
}
 
// --- End NeoPixel
/** @} */
 

GeSHi © Codebox Plus Extension

Posted: **Thu May 02, 2019 2:37 am**

FWIW, while this may be an interesting example, the ESP32 has a bunch of peripherals that are better at doing this than dedicating a core to it... the RMT, I2S and SPI peripherals all have been used to do this with minimal CPU overhead; various libraries are available for this.

Posted: **Thu Jun 06, 2019 1:53 pm**

Very interesting thanks for your code example.
I've also started a project using Neopixels to receive short UDP messages and launch fast animations
https://github.com/martinberlin/Remora

I would like to send signals from Orca sequencer

Posted: **Mon Oct 07, 2019 3:55 pm**

Totally agree with ESP_Sprite.

Note that if you are using Neopixels Makuna library there is a I2S bug that is sometimes not refreshing the leds correctly. Use the RMT methods for the ESP32. Then you can have as much as 8 channels and control a lot of pixels.

ESP32 Forum

Dimming Neopixels, Delays<Microseconds

Dimming Neopixels, Delays<Microseconds

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Re: Dimming Neopixels, Delays<Microseconds