Friday, December 9, 2011

Multiplexer

After conversing with someone who was working with lots of LED circuits, they suggested a demultiplexer circuit using latches to remember the state of the LED's so that less ports are needed and ports inputs can be changed quickly. The reference used was:

http://www.instructables.com/id/Led-Cube-8x8x8/step8/IO-port-expansion-more-multiplexing/

However, the circuit in the HC12 triggered an Illegal BP every iteration and occasionally would not even run and gave an HI-WAVE MCU clock not detected error. We discussed among ourselves and decided that the latches would not help us anyway, since we want the LED's to be lit for the same duration, and having the earlier lit LEDs stay on until the last LED is lit and the system starts over would be bad, unless we specifically programmed in software for each latch to clear after a certain duration, which would make the software more complicated.

Hence, we decided to stay with our original circuit, due to time constraints, and have the more complicated multiplexer circuit as future possible expansion.

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