FastLED Modified Blend to Target Color - HSV - Flickering between Value changes

[sharonrlevy]

@PaulRB, I implemented your code update, and it didn't get rid of the flicker but it seemed to change it, mading it more recognizable as a pattern like - dim, bright, dim, dim, bright. I'm attaching the plotter data and serial data I got. Unfortunately, the lights kept getting stuck at red, unless I took it off the USB power, and then I can't plot the data. (I'm trying to post the serial data but I'm limited to 9000 characters so have to delete most of it)

Setup done. 

128 90 50
colorCurrent: 128 colorTarget: 100 k: 0
colorCurrent: 128 colorTarget: 100 k: 1
colorCurrent: 128 colorTarget: 100 k: 2
colorCurrent: 128 colorTarget: 100 k: 3
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[sharonrlevy]

@david_2018 that looks way better! It's still a bit halting between the value changes, like new color, new color new color, instead of a smooth flow, but it is no longer flickering. I'm attaching the plotter data. This is a big improvement! Any ideas of a way to continue smoothing the value changes? I tried slowing the blend rate, but that made it even more obvious.

[Grumpy_Mike]

Any ideas of a way to continue smoothing the value changes?

I would use floating point variables to do the calculations and only change them into integer values when addressing the hardware.

[PaulRB]

the lights kept getting stuck at red, unless I took it off the USB power

You can't really run 60 RGB leds on usb power alone, it's normally limited to 500mA. 60 leds could need as much as 3,600mA if they are all set at max brightness white. So if you are powering the strip by usb power alone, this could be why they all stick at red: the 500mA max is being exceeded and the voltage is dropping to a level where only the red LEDs light.

What you need to do is connect your 5V PSU to the strip only and power just the Arduino with usb. Only the ground wire and the data wire connecting the Arduino to the strip. Then you can monitor the Arduino and have the strip light correctly all through the sequence.

Of course, if you just want to monitor the Arduino, you can disconnect the strip. The Arduino has no way to tell if the strip is connected or not, and will output the same data regardless.

I could not understand the serial plotter screens you posted. What exactly were the different lines the plot? On the one I posted earlier, blue was hue, yellow was sat and red was Val.

Can you try something? Make all the colours in your sequence identical and let it run. Do you see any flickering?

[david_2018]

Some of the flickering seems to be caused by the conversion from HSV to RGB in FastLED. Even when doing the calculations for the blend in the sketch to eliminate the jitter in the HSV numbers, the LEDs still produce a bit of flicker, particularly when more than one of the R G or B values change at the same time.

#include "FastLED.h"
#define DATA_PIN    7
//#define CLK_PIN     13
#define LED_TYPE    WS2813
#define COLOR_ORDER GRB
#define NUM_LEDS    60
//#define BRIGHTNESS  255
CRGB leds[NUM_LEDS];

uint8_t blendRate = 50;  // How fast to blend.  Higher is slower.  [milliseconds]

CHSV color1 = CHSV(128, 90, 50);
CHSV color2 = CHSV(64, 50, 80);
CHSV color3 = CHSV(32, 200, 190);
CHSV color4 = CHSV(192, 200, 190);
CHSV color5 = CHSV(160, 90, 190);
CHSV color6 = CHSV(100, 100, 80);

const byte number_of_colors = 6;
int current_color_index = 0;

CHSV color_array[number_of_colors] = {color1, color2, color3, color4, color5, color6};


//adjust color start CHSV and colorTarget CHSV to match colors above
CHSV colorStart = CHSV(128, 90, 50); // starting color
CHSV colorTarget = CHSV(100, 100, 80); // target color
CHSV colorCurrent = colorStart;




//---------------------------------------------------------------
void setup() {
  Serial.begin(115200);  // Allows serial monitor output (check baud rate)
  delay(3000); // 3 second delay for recovery
  //FastLED.addLeds<LED_TYPE,DATA_PIN,COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  //FastLED.setBrightness(BRIGHTNESS);
  Serial.println("Setup done. \n");
}

//---------------------------------------------------------------
void loop()
{
  EVERY_N_MILLISECONDS(blendRate) {
    static uint8_t k;
    if (( colorCurrent == colorTarget ) && (k == 0)) {  // Check if target has been reached
      colorStart = colorCurrent;
      colorTarget = color_array[current_color_index];  // new target to transition toward
      current_color_index += 1;
      if (current_color_index == number_of_colors) {
        current_color_index = 0;
      }
      k = 0;  // reset k value
      //Serial.print("New colorTarget:\t\t\t"); Serial.println(colorTarget.h);
    }


    colorCurrent = blend(colorStart, colorTarget, k, SHORTEST_HUES);
    byte deltaHue = (colorTarget.hue - colorStart.hue);
    byte newHue;
    if (colorTarget.hue > colorStart.hue) {
      if (deltaHue < 128) {
        newHue = (uint32_t)colorStart.hue + (((((uint32_t)colorTarget.hue - (uint32_t)colorStart.hue) * 10 * (uint32_t)k / 255u) + 5) / 10);
      } else {
        newHue = (uint32_t)colorStart.hue - ((((256u - (uint32_t)colorTarget.hue + (uint32_t)colorStart.hue) * 10 * (uint32_t)k / 255u) + 5) / 10);
        //Serial.println(256u -(uint32_t)colorTarget.hue + (uint32_t)colorStart.hue);
      }
    } else if (colorTarget.hue < colorStart.hue) {
      if (deltaHue >127) {
        newHue = (uint32_t)colorStart.hue - (((((uint32_t)colorStart.hue - (uint32_t)colorTarget.hue) * 10 * (uint32_t)k / 255u) + 5) / 10);
      } else {
        newHue = (uint32_t)colorStart.hue + ((((256u - (uint32_t)colorStart.hue + (uint32_t)colorTarget.hue) * 10 * (uint32_t)k / 255u) + 5) / 10);
      }
    } else { //colorStart.hue == colorTarget.hue
      newHue = colorStart.hue;
    }
    byte newSat;
    if (colorTarget.sat > colorStart.sat) {
      newSat = (uint32_t)colorStart.sat + (((((uint32_t)colorTarget.sat - (uint32_t)colorStart.sat) * 10 * (uint32_t)k / 255u) + 5) / 10);
    } else if (colorTarget.sat < colorStart.sat) {
      newSat = (uint32_t)colorStart.sat - (((((uint32_t)colorStart.sat - (uint32_t)colorTarget.sat) * 10 * (uint32_t)k / 255u) + 5) / 10);
    } else { //colorStart.sat == colorTarget.sat
      newSat = colorStart.sat;
    }
    byte newVal;
    if (colorTarget.val > colorStart.val) {
      newVal = (uint32_t)colorStart.val + (((((uint32_t)colorTarget.val - (uint32_t)colorStart.val) * 10 * (uint32_t)k / 255u) + 5) / 10);
    } else if (colorTarget.val < colorStart.val) {
      newVal = (uint32_t)colorStart.val - (((((uint32_t)colorStart.val - (uint32_t)colorTarget.val) * 10 * (uint32_t)k / 255u) + 5) / 10);
    } else { //colorStart.val == colorTarget.val
      newVal = colorStart.val;
    }
    //fill_solid( leds, NUM_LEDS, colorCurrent);
    fill_solid( leds, NUM_LEDS, CHSV(newHue, newSat, newVal));
    leds[0] = colorTarget;  // set first pixel to always show target color
    //Serial.print("colorCurrent:\t"); Serial.print(colorCurrent.h); Serial.print("\t");
    //Serial.print("colorTarget:\t"); Serial.print(colorTarget.h);
    //Serial.print("\tk: "); Serial.println(k);
    char buf[60];
    //sprintf_P(buf, PSTR("H:%3i S:%3i V:%3i    R:%3i G:%3i B:%3i    k:%3i"), colorCurrent.h, colorCurrent.s, colorCurrent.v, leds[1].r, leds[1].g, leds[1].b, k);
    //sprintf_P(buf, PSTR("H:%3i S:%3i V:%3i    R:%3i G:%3i B:%3i    k:%3i"), newHue, newSat, newVal, leds[1].r, leds[1].g, leds[1].b, k);
    //Serial.println(buf);
    sprintf_P(buf, PSTR("%3i %3i %3i"),newHue, newSat, newVal);
    Serial.println(buf);

    FastLED.show();  // update the display
    k++;
  }

}

[sharonrlevy]

@Grumpy_Mike - sorry I don't understand what you mean (I'm a real novice here).

@PaulRB - Oh yes, I normally have it powered by a 5V, but I didn't realize the lights didn't even need to be plugged in for the Plotter to plot. That being said, I have no idea what any of that plotting data is communicating

@david_2018 - I wanted to use HSV so that I could have more control over the Saturation and Value. But if this is creating all of the problems, could this code be converted to RGB mode, and still have a way to modulate brightness? Also, is there anything new in the code you posted most recently?

And to all of you, I can't thank you enough for the help you are giving me.

[sharonrlevy]

In response to @PaulRB - if I make all of the H,S,V values the same, there is is no flickering, just a solid color.

If I make all of the values the same but change the color, I get a smooth blend from one color to the next. Well there's a tiny bit of flicker, but not that significant.

I tried the code from @david_2018's most recent post and no difference.

[Grumpy_Mike]

sorry I don't understand what you mean (I'm a real novice here)

The way you have it all the calculations are done with integers. This leads to rounding errors because all the incrementing can only be to the closest integer. To get fraction numbers you need to use floating point numbers. We tend to shy away from these with a micro controller because they take a lot longer to do and most of the time they are not what you want.

However here they are what you need.

int - Arduino Reference

float - Arduino Reference

[PaulRB]

I don't think switching to RGB is going to help. After all, that's what FastLED is doing behind the scenes anyway. The LEDs themselves work in RGB, you are working in HSV and FastLED is translating.

I'm still surprised you can even see the flickering at all, except perhaps when the LEDs are at very low brightness. The magnitude of the jitter in the data is one unit, the smallest possible. But that just is in the HSV space. Maybe in the RGB space it is much more significant. That's something to investigate.

[PaulRB]

Here is the first few seconds of the sequence as hue (blue line), sat (yellow line) and val (red line):

And now here is the same few seconds as red (blue line), green (yellow line) and blue (red line):

(Sorry about the confusing choice of colours, but I don't think serial plotter allows you to take control over them, you are stuck with the ones it has).

So its now clearer to me why you are seeing the flickering. It does look much worse in RGB colourspace.

I'm becoming convinced that Mike is right, the integer maths that FastLED is using to blend colours and to convert between colourspaces is the problem here. There is some jitter in the HSV values, so even if the conversion to RGB was perfect, there would still be some flicker. But it might be acceptably small, is hard to guess.

So there are a couple of options, I think.

1. Raise an issue against FastLED on github and wait/hope the author can fix it.
2. Switch to using RGB objects in FastLED and write or find some HSV-->RGB conversion and colour blending code so that you don't rely on FastLED's blend() and colourspace conversion.

[PaulRB]

Try this version. I changed the code so that the blend happens in RGB colourspace.

#include "FastLED.h"
#define DATA_PIN    7
//#define CLK_PIN     13
#define LED_TYPE    WS2813
#define COLOR_ORDER GRB
#define NUM_LEDS    60
//#define BRIGHTNESS  100
CRGB leds[NUM_LEDS];

uint8_t blendRate = 50;  // How fast to blend.  Higher is slower.  [milliseconds]

CHSV color1 = CHSV(128, 90, 50);
CHSV color2 = CHSV(64, 50, 80);
CHSV color3 = CHSV(32, 200, 190);
CHSV color4 = CHSV(192, 200, 190);
CHSV color5 = CHSV(160, 90, 190);
CHSV color6 = CHSV(100, 100, 80);

int number_of_colors = 6;
int current_color_index = 0;

CHSV color_array[6] = {color1, color2, color3, color4, color5, color6};


//adjust color start CHSV and colorTarget CHSV to match colors above
CRGB colorStart = color1; // starting color
CRGB colorTarget = color2; // target color
CRGB colorCurrent = colorStart;

//---------------------------------------------------------------
void setup() {
  Serial.begin(115200);  // Allows serial monitor output (check baud rate)
  delay(3000); // 3 second delay for recovery
  //FastLED.addLeds<LED_TYPE,DATA_PIN,COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  //FastLED.setBrightness(BRIGHTNESS);
  Serial.println("Setup done. \n");
}


//---------------------------------------------------------------
void loop()
{
  EVERY_N_MILLISECONDS(blendRate) {
    static uint8_t k;
    if ( colorCurrent == colorTarget ) {  // Check if target has been reached
      colorStart = colorCurrent;
      colorTarget = color_array[current_color_index];  // new target to transition toward
      current_color_index += 1;
      if (current_color_index == number_of_colors) {
        current_color_index = 0;
      }
      k = 0;  // reset k value
      //Serial.print("New colorTarget:\t\t\t"); Serial.println(colorTarget.h);
    }

    colorCurrent = blend(colorStart, colorTarget, k);
    fill_solid( leds, NUM_LEDS, colorCurrent );
    //leds[0] = colorTarget;  // set first pixel to always show target color
    //Serial.print("colorCurrent:\t"); Serial.print(colorCurrent.h); Serial.print("\t");
    //Serial.print("colorTarget:\t"); Serial.print(colorTarget.h);
    //Serial.print("\tk: "); Serial.println(k);
    //CRGB colorCurrentRGB = colorCurrent;
    //Serial.print(colorCurrentRGB.r); Serial.print(" "); Serial.print(colorCurrentRGB.g); Serial.print(" "); Serial.println(colorCurrentRGB.b);
    k++;
    FastLED.show();  // update the display
  }

}

[david_2018]

PaulRB:
I'm becoming convinced that Mike is right, the integer maths that FastLED is using to blend colours and to convert between colourspaces is the problem here. There is some jitter in the HSV values, so even if the conversion to RGB was perfect, there would still be some flicker. But it might be acceptably small, is hard to guess.

The math in FastLED appears to mostly be done with 8-bit integers, with a primary objective being speed, so that something like blend can be applied to large numbers of LEDs quickly. The flicker is most noticeable at low brightness, particularly when more than one color changes level simultaneously. With hue, saturation, and value all varying, there are times when the value for a particular RGB color will go up, down, then up again.

[Grumpy_Mike]

I changed the code so that the blend happens in RGB colourspace.

You get a whole different set of colours depending on which colour space you do the blend in. I wrote different space blending examples in my Raspberry Pi for dummies edition 3 book.

It is traversing a different colour space that makes the blends so interesting. Not just RGB and HSV but there are other colour spaces as well. All produce different colours and they all blend seamlessly.

[PaulRB]

Realise that, Mike, but thought the OP might be happy with the RGB blending, especially if it fixes the flickering problem.

[sharonrlevy]

@PaulRb, I do think that RGB version is slightly more fluid in the value transitions. Not miraculously different, but minutely. In both your RGB conversion version and the last version from @david_2018 there is no flickering; they both have a little bit of lurching between the value changes, but the RGB one might have slightly less.

@Grumpy_Mike thanks, I just don't know how to fix this as I'm really not a coder. Any suggestions are extremely welcome.

I guess it might be work letting the developer know about the issue and see what happens.

I definitely feel so much better about where this is at, and I can't thank you all enough!

[PaulRB]

a little bit of lurching between the value changes

I wonder if that could be the 8-bits-per-colour resolution of all addressable strips. Only 256 intensity levels are available in each of the red, green and blue channels. Because the eye is not linear, a difference level of 1 is not noticeable for levels over about 100, but for low levels, it can be very noticeable indeed. For example level 2 is obviously twice as bright as level 1!

I seem to remember FastLED has a "temporal dithering" feature which might help. I've never used it, but here's a link.

[PaulRB]

Non-addressable RGB strips don't have the 8-bit limitation. Maybe that would be a better option for your project, given that you are setting all LEDs to the same colour, you don't need addressable LEDs.

With non-addressable strips, the driver circuits that control the intensity levels in the red, green and blue channels are external to the strip, you have to build our buy them. The most basic driver circuit consists of 3 MOSFETs connected to 3 Arduino PWM pins. By default, Arduino PWM pins are also 8-bit resolution, so that would be no better than what you have now. But if you used an external PWM chip, or maybe an Arduino with a faster more powerful chip, such as an Arduino Zero, Teensy 3.x or similar, you could achieve 10 or 12 bit resultion, which would mean 4 or 16 times as many intensity levels.

[sharonrlevy]

@PaulRB - sorry for the delayed response.
That's an interesting idea. I chose the addressable strips because I'd thought to do more complicated things witht hem, until I realized how complicated the "simple" things are!
If I changed strip type would I still use the same code, or would I need to make adjustments (aside from the strip type, pin, etc)

[Grumpy_Mike]

If I changed strip type would I still use the same code

No.

would I need to make adjustments

It would have to be completely rewritten depending on the type of strip you got. Strips that do not contain addressable LEDs do not need a library at all.

[sharonrlevy]

thanks @Grumpy_Mike. I'll try and make what I have work, otherwise I'll be back on this board with a whole new set of questions!