First light on the matrix

First milestone: get the panel lit and individually addressable. The panel is wired in a serpentine pattern, so even rows run left-to-right and odd rows right-to-left. Without accounting for that, text comes out mirrored on every other row. The mapping that fixed it:

uint16_t xyToIndex(uint8_t x, uint8_t y) {
  return (y % 2 == 0) ? y * 16 + x : y * 16 + (15 - x);
}

With that in place I could light arbitrary (x, y) pixels and start laying out where each word sits on the grid.

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This update is part of LED Matrix Word Clock. See the full build log or browse all project logs.