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Has anybody built a BLM with bidirectional two lead duocolor LEDs, where the two colors can be adressed by reversing the polarity? How would the scan circuit have to be designed in order to work with the standard midibox solutions? Of course, compared with the scalar board, the resistor-transistor arrangement of IC2 could be placed next to IC3 and another 74HC595 next to IC2. But then the scan algorythm would also have to scan each color sequentially. Why am I looking for such a solution? I evaluated the the switch of choice for my Synth project: For my needs, I only have single color buttons (yellow). But this button could also be interesting for BLM applications where duocolor would be needed (RGB is available as well). I am working on a versatile matrix PCB solution for my synth project, where single rows of a matrix can be cut to the desired length and the LEDs can be adressed individually via solder jumpers. These smaller boards can be bought much cheaper in small quantities than the propriatary matrix boards and in my case serve different needs.