Oct 132012

The blinky pov uses a neat little trick to program new words and symbols into the blinky pov to 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

Programming my blinky pov is not working, it’s as simple as that. There are a variety of reasons why programming might not work, from hardware issues to software issues. Either the data is not getting to the programmer or the programmer is not interpreting or programming properly.

The first place to look is the output of the sensor. Is the sensor generating Highs and Lows, 1s and 0s. Hooking an oscilloscope to the SCLK and SDAT lines generated the captures below.

First I hooked up SCLK and tried to program from my desktop monitor. It is a Samsung SyncMaster P2770. It supposedly has a 1ms response time and 70,000:1 contrast. The hookup and traces look like this…

Each burst of activity on the scope is a SINGLE clock pulse. One flash of white from the blinky pov web programming application.

Looking at the various scope traces it is clear the incoming data is neither a 1 nor a 0. This group of traces is from my main desktop monitor running Google Chrome at the Blinky POV programming website.

scope hookup desktop

The traces above are from Google Chrome. Somewhere in the random postings on the blinky pov forums was an assertion that different web browsers will display the white and black squares differently and thereby affect blinky pov programming performance.

The following traces are from the same monitor, at the same height, in the same lighting conditions, at the same distance from the monitor. These captures are from running Mozilla Firefox.

The trace above is with Firefox and the room lights on. It was also recommended to turn the room lights off. The trace below is the exact same setup as above with the room lights turned off.

So far what I’m taking away from the various recommendations to try different browsers and lighting is that it is a smokescreen. I’m not seeing a difference in traces when trying to program from the same monitor.

Switching back to Google Chrome and pointing at my second desktop monitor, a Samsung SyncMaster P2350 produced the following traces.

Using Firefox and hooking the scope to the data line (SDAT) produced these traces.

Next I tried my netbook. It is an Acer Inspire One. The scope hookup was the same, the browser was Google Chrome pointed to the W&L Blinky POV programming website. This time I do see a difference. The light to dark transition from the netbook is much stronger and also has a much higher frequency carrier.

Switching to Firefox on the netbook produced similar results as on the desktop, that is, no real change.

Switching to a smart phone produced an interesting difference and probably explains why we had any success at all when using a smart phone to program the blinky pov.

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