Individual panel color tuning support?

echamberlain · March 1, 2017, 2:42am

Hello,

I have four panels in a 64x64 configuration. The same color on different panels (e.g., white) noticeably differs. Does SmartMatrix have support for tuning each panel to get the colors to match?

I’d be happy to work on a pull request, if someone can point me to the relevant code sections.

Louis · March 9, 2017, 9:42pm

There’s no support for this. Here’s the code (assuming you’re refreshing with 36-bit color) that pulls pixel data from layers and puts it in a row buffer before shifting it out to the panels. You could put some color balancing code in here.

github.com

pixelmatix/SmartMatrix/blob/master/src/SmartMatrix_Impl.h#L932




        //o3.p3clk = 0;
        //o3.p3pad = 0;
        o3.p3b1 = temp0blue    >> (3 + 3 * sizeof(uint32_t));
        o3.p3r1 = temp0red     >> (3 + 3 * sizeof(uint32_t));
        o3.p3r2 = temp1red     >> (3 + 3 * sizeof(uint32_t));
        o3.p3g1 = temp0green   >> (3 + 3 * sizeof(uint32_t));
        o3.p3g2 = temp1green   >> (3 + 3 * sizeof(uint32_t));
        o3.p3b2 = temp1blue    >> (3 + 3 * sizeof(uint32_t));


        *(++tempptr) = o3.word;
        *(tempptr + latchesPerRow/sizeof(uint32_t)) = o3.word | clkset.word;
    //}
}


#if (ADDX_UPDATE_BEFORE_LATCH_BYTES > 0)
union {
    uint32_t word;
    struct {
        // order of bits in word matches how GPIO connects to the display
        uint32_t GPIO_WORD_ORDER;

Alternatively, you could put it in the fillRefreshRow code inside one of the layers, but that would only alter the colors for that layer.

Maybe you can take some code or techniques from FastLED’s color balancing: https://github.com/FastLED/FastLED/wiki/FastLED-Color-Correction

echamberlain · March 9, 2017, 10:03pm

Thanks for the info. I’m already using FastLED for HSV support, I’ll take a look at its color correction code.

pinballsp · June 22, 2017, 4:28am

Problem may be some panels are RGB and some are RBG, so blue and green are exchanged. If its the problem then you will must to change connections in panel that is different.

I have here some P2.5 led panels, some RGB, some RBG, then when play same, colors are different in each panel, green exchange by blue, yellow by pink, etc…

At any rate, white color must to be always same in all led panels because mix the three basic colors RGB.

Louis · June 22, 2017, 5:01am

Sounds like a mistake in hardware to me. The HUB75 pinout sets pin positions for R G and B and the manufacturer didn’t follow it. I would fix it in hardware as well, making custom cables to swap the colors to and from the panels that need it. You could minimize the number of custom cables needed by grouping similar panels

pinballsp · June 22, 2017, 2:14pm

Some manufacturers, currently do RBG panels instead of RGB. I know HUB75 pinout define clearly each pin position, and this may be some problem for designs based on HUB75.

Currently I order in quantity, P2.5 LEd panels from a manufacturer, and recently he changed design to improve it, but also he changed the data pinout, and now the new design is RBG instead of RGB. I realized about it, when connected to my custom board and all colors were different. Also the manufacturer changed the position of data and power supply connectors, so I had to modify two times my PCB design.