When the colours are wrong

Diagnose it before you change anything

Fill the screen with pure red, then green, then blue, and leave a black bar somewhere you can see. Then read the symptom.

Three symptoms, three causes, and the black bar is what separates them.

Black is the tell

If black is still black, only the channel order is wrong. The panel wants its three colour channels in the opposite order from the one being sent, so red and blue trade places and green — which sits in the middle — is unaffected. That is setColorOrder().

If black has come out white, the panel is inverted. Every value is being displayed as its opposite, which is a single bit in the controller and a single call: setInverted().

If red is arriving as yellow, both are wrong at once. It looks exotic and it is not: invert red and you get cyan, then swap cyan's channels and you get yellow. Two calls, and the arithmetic is worth following once so the symptom is recognisable on sight.

The two calls, and when

Both are single register writes, so they work at any time, before or after begin(), on every controller in these boards. A test sketch can sweep them without recompiling.

LB_Display display(LB_TFT_18);

void setup() {
  display.begin();
  display.setColorOrder(LB_Display::COLOR_BGR);   // red and blue swapped
  display.setInverted(true);                      // black coming out white
}

setColorOrder() still returns a bool so that older sketches compile; it is always true. printInfo() reports both settings and marks either one (forced) when you have overridden the table.

Why this article exists at all

The panel table that makes every other part of this book a one-line change is honest about its own limits: the colour order and inversion flags in it have not been measured on these boards. The library's own file says so in a warning at the top, and marks the colour order of one panel outright as unverified. The old Arduino sketches and the old MicroPython scripts disagreed about it, and nobody noticed for a long time because the test drew unlabelled colour bars. You cannot tell red from blue in a bar with no caption.

This book does not print the flags for that reason. What is true whatever they turn out to be is the symptom table above. Run the self-test, look at the named screens, and if a board is wrong you now know which call to reach for.

And if it is a board we sell, say so rather than working around it in your sketch. The value belongs in panels.yaml, where both languages pick it up and the next person does not have to find it again.