Dimming Neopixels, Delays<Microseconds

[HelWeb]

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]

1. // ----------- NeoPixel -------------
2. //---------- WS2812B.pdf ------------
3.  
4. inline void BitL(int lp) {
5. int ii;
6.   gpio_set_level( RTOS_PinNeo, 0);
7.   for (ii=0; ii<lp; ii++) {
8.     asm(" nop");
9.   }
10.  
11. }
12.  
13. inline void BitH(int lp) {
14. int ii;
15.   gpio_set_level( RTOS_PinNeo, 1);
16.   for (ii=0; ii<lp; ii++) {
17.     asm(" nop");
18.   }
19. }
20.  
21. inline void Bit1() {
22.   BitH(21);            
23.   BitL(6); // 21/6      // from experiments
24. }
25.  
26. inline void Bit0() {
27.   BitH(8);
28.   BitL(20); // 8/20
29. }
30.  
31.  
32. inline void Color( uint32_t c) {
33. int i;
34.   for (i=0;i<24;i++) {
35.     if (c & 0x800000 ) Bit1();
36.     else Bit0();
37.     c<<=1;
38.   }
39. }
40.  
41. /**
42.  * \name NeoPix
43.  * @{
44.  * Dimming Blink of NeoPixel, 3 colors: red, green, blue
45.  *
46.  * \hideinitializer
47.  *
48.  */
49.  
50. void NeoPix( void * pvParameters ) {
51. uint32_t c=0, cc=0;
52. int up=1;
53. unsigned int state=0;
54.   gpio_set_direction(RTOS_PinNeo, GPIO_MODE_OUTPUT );  // Data-Pin of NeoPixel
55.   c=0x01;
56.   while(1) {
57.       portDISABLE_INTERRUPTS();
58.       Color(cc);
59.       BitL(2);
60.  
61.       //SentColors++; // for testing
62.       // Dimming and blinking ...
63.       if (up) { c+=1;  if (c>=0xfe)     up=0;}
64.       else    { c-=1;  if (c==0x000000) { up=1; state+=8;} } // BRG: shift  0, 8, 16
65.       if (state>16) state=0;
66.       cc = (c<<state);
67.       portENABLE_INTERRUPTS();
68.       vTaskDelay(1);
69.   }
70.  
71. }
72.  
73. // --- End NeoPixel
74. /** @} */
75.  

GeSHi © Codebox Plus Extension

[ESP_Sprite]

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.

[fasani]

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

[fasani]

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.