ukflyer

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• Newbie question regarding loops

  @ukflyer started

  • 8 comments
  • 2,807 views

  @Spocki replied
• Newbie question regarding loops

  in JavaScript • 8 years, 10 months

  

  Okay maybe not the most exciting pattern but here is what I ended up with -

  SPI2.setup({baud:3200000, mosi:B15});  // setup SPI port
  
  var pos = 0;        // select start point
  var direction = 1;  // set direction of travel, 1 forwards and -1 backwards
  var width = 4;      // set width of pattern
  var length = 50;    // set length of led string
  
  var rgb = new Uint8ClampedArray(length*3);  // setup array for leds
  
  function step() {
    if (pos > width && direction == 1 ) {        // if we have lit the pattern width and are travelling forwards
      rgb[(pos-(width*3))] = 0;                    // then blank the first led in the pattern
      rgb[(pos-(width*3)+1)] = 0;
      rgb[(pos-(width*3)+2)] = 0;
    }
    if (pos < rgb.length && direction == -1 ) {  // if we haven't reached the end of the string and travelling backwards
      rgb[(pos+(width*3))] = 0;                    // then blank the last led in the pattern
      rgb[(pos+(width*3)+1)] = 0;
      rgb[(pos+(width*3)+2)] = 0;
    }
    rgb[pos ] = 255;                             // set the next led in the pattern to red
    rgb[pos+1] = 0;
    rgb[pos+2] = 0;
  }
  
  function doStep() {
    step();                                      // set next step in the pattern
    pos+=(3*direction);                          // step to the next position
    if (pos >= rgb.length) {                     // if we have gone passed the last led
      direction = -1;                              // reverse the direction
    }
    if (pos < 0) {                               // if we have gone passed the first led
      direction = 1;                               // reverse the direction
    }
  }
  
  function send() {
    SPI2.send4bit(rgb, 0b0001, 0b0011);          // send the data to the led string
  }
  
  setInterval(function() {
    doStep();
    send();
   }, 18);
  
  

• Newbie question regarding loops

  in JavaScript • 8 years, 10 months

  

  @DrAzzy
  That's sorted it !!

  Thanks for pointing me in the right direction.

• Newbie question regarding loops

  in JavaScript • 8 years, 10 months

  

  @DrAzzy
  I understand the parameters of setTimeout now, but if I place it outside of the loop surely I will only ever light the last two lights ?

  The timeout is needed to delay the step otherwise the pattern will complete in a flash, if you will forgive the pun !

  Thanks

• Newbie question regarding loops

  in JavaScript • 8 years, 10 months

  

  Hi,

  I apologise in advance for this simple question.

  I have just taken delivery of two strings of 50 WS2811 led's.

  I can get all the sample code working and I have managed to extend the patterns of blinking but now I would like to try stepping patterns, ie light the first two led's and then step forwards lighting one led at a time and turning off the first led so that only two leds are lit at any one time.

  Here is the code that I am playing with -

  SPI2.setup({baud:3200000, mosi:B15});
  
  var rgb = new Uint8ClampedArray(50*3);
  
  
  function step(pos) {
    if (pos > 0) {
    rgb[pos-1] = 0;
    }
    rgb[pos ] = 0; 
    rgb[pos+1] = 0;
    rgb[pos+2] = 255;
    rgb[pos+3] = 0; 
    rgb[pos+4] = 0;
    rgb[pos+5] = 255;
  }
  
  function doStep() {
    for (var i=0;i<rgb.length-3;i+=3) {
      step(i);
      setTimeout(SPI2.send4bit(rgb, 0b0001, 0b0011), 5000);
    }
  }
  

  I know its ugly but I am just playing at the moment.

  When I execute this the first two leds light and I get the following error -

  Uncaught Error: Function or String not supplied:
   at line 4 col 56
  

  Any pointers would be gratefully appreciated.