Inside each segment is 3 red/green/blue LEDs, for 21 LEDs total. The anodes are all connected together and then there are 21 cathodes to control. Unfortunately that means you’ll need 21 pins to fully control the display, and we do not have a backpack or easy solution at this time. We suggest 3 75HC595’s (or similar) chained together so you can control 24 pins with a 3-pin SPI interface. That will let you light up each segment’s LED separately. The decimal point is not connected (does not light up) on this display, only the seven segments.
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