Salut @tobozo,

I liked the way you represented WiFi channel saturation with your WiFiChanViz app that I discovered on Twitter:

So I challenged myself to try to remake it by myself for the ESPboy. I kept your idea of setting the height of the channels according to the number of access points occupying them. But I chose a different color scale depending on the best-observed signal quality for each channel.

And I added the ability to browse between channels to see the list of access points broadcasting a WiFi network.

Here is how it looks:

Well, the WiFi antenna of the M5Stack is probably of better quality than the one of the Wemos D1 mini that drives the ESPboy...

I then took a look at your code to compare our approaches. They are pretty similar, although we have a different way of calculating the luminance for the historical perspective fade:

// --------------------------------------------------------
// tobozo's method
// --------------------------------------------------------

// luminosity reducer, taken from Bodmer's antialiased font
static uint16_t luminance(uint16_t color, uint8_t luminance)
{
  // Extract rgb colours and stretch range to 0 - 255
  uint16_t r = (color & 0xF800) >> 8; r |= (r >> 5);
  uint16_t g = (color & 0x07E0) >> 3; g |= (g >> 6);
  uint16_t b = (color & 0x001F) << 3; b |= (b >> 5);

  b = ((b * (uint16_t)luminance + 255) >> 8) & 0x00F8;
  g = ((g * (uint16_t)luminance + 255) >> 8) & 0x00FC;
  r = ((r * (uint16_t)luminance + 255) >> 8) & 0x00F8;

  return (r << 8) | (g << 3) | (b >> 3);
}

// Use as a gfx replacement for tft.fillScreen(TFT_BLACK).
// Produces a strobe effect by reducing luminosity on all non-black pixels.
// Limitations:
//  - 16bits colors only
//  - Only fades to black
//  - frame rate must be >15fps
//  - Sluggish when the sprite has too many (>50%) non black pixels
static void spriteFadeOut( LGFX_Sprite *sprite, uint8_t strength )
{
  int32_t w = sprite->width();
  int32_t h = sprite->height();
  int32_t l = w*h;
  uint16_t* framebuf = (uint16_t*)sprite->getBuffer();
  for( uint32_t i=0;i<l;i++) {
    if( framebuf[i]!=TFT_BLACK ) {
      uint16_t pixcolor = (framebuf[i] >> 8) | (framebuf[i] << 8);
      pixcolor = luminance( pixcolor, strength );
      framebuf[i] = pixcolor<<8 | pixcolor>>8;
    }
  }
}

// --------------------------------------------------------
// m1cr0lab's method
// --------------------------------------------------------

uint16_t * const fb  = (uint16_t*)fb1->getBuffer();
uint16_t   const len = GRAPH_WIDTH * GRAPH_HEIGHT;
uint16_t color;
uint8_t. r, g, b;
for (uint16_t i = 0; i < len; ++i) {
    if (fb[i]) {
        // swaps endianness
        color = fb[i] >> 8 | fb[i] << 8;
        // extracts the primary colors
        r = color >> 11;
        g = (color >> 5) & 0x3f;
        b = color & 0x1f;
        // lowers luminance
        r = r > 1 ? r - 1 : 0;
        g = g > 2 ? g - 2 : 0;
        b = b > 1 ? b - 1 : 0;
        // repacks the RGB565 color
        color = r << 11 | g << 5 | b;
        // restores endianness
        fb[i] = color << 8 | color >> 8;
    }
}

LovyanGFX library is outstanding!

Oh, and I have to point out a slight error in your WiFiChanViz.ino code:

for (int i = 0; i < n; ++i) {
    int32_t channel = WiFi.channel(i);
    dpc[channel]++;
}

Replace this:

dpc[channel]++;

By:

dpc[channel - 1]++;

If you are curious, you can have a look at my code.

En tout cas, merci pour ton travail inspirant ! :wink:

Steph