Oct 132012

To repeat the intro to the last post, the blinky pov uses a neat little trick to read in new words and symbols to program into the blinky pov display.

Two light emitting diodes are mounted on the blinky pov and used in a fashion that causes them to act as light receptors rather than the traditional LED use as light emitters.

Sensing Leds Sensing Leds

SCLK and SDAT, the incoming program data clock and data lines, are wired to pins RA2 (pin 11) and RA4 (pin 3).

SCLK and SDAT pins Chip Pins 3 and 11

Normally we think of digital signals as ON or OFF, digital data is a 1 or it is a 0. Unfortunately reality intrudes and 1 and 0 do not apply. Looking at the previous post we can see the clock and data signals presented to the blinky pov processor are decidedly not clean 0s and 1s.

Pins RA2 and RA4 can be, and are in the blinky pov, configured as analog input pins. Looking at the traces from the previous post there appears to be a good reason for wiring the clock and data to analog input pins.

(More to come here….. I’m looking at the code and I see some effort to calibrate for the black level….)

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