I some some sample DycoLEDs (http://www.kirronlightcomponents.com/index.php/download_file/view/63/83/) that I'm playing with and one of the annoying things I've discovered is that when you apply VCC and GND, they immediately come on bright white. They're not like some other LED ICs that turn on with all channels in an "off" state. Whether the signal lines are connected or not, all you'd have to do is add VCC and GND, and the thing turns the LED on. And for the fraction of a second it takes the Arduino bootloader to kick the sketch into running, you're left with the LED (or LEDs if you have a bunch of them) bright white.
So, I'm wondering if there's anything that can be done to mitigate that.
I'm not sure on the delaying VCC part. Even if I wanted till the MCU started sending data, the micro/milli second it takes between applying VCC to the string and the MCU data reaching it will still leave you with the entire string being bright white.
As for pull-ups/downs, I don't think that matters. For one, the datasheet does not indicate that any is needed, anywhere, nor caps. For that matter, it doesn't say anything about having pull-ups at the end of the line to avoid reflection either (one of the many questions I have sent to the manufacturer.) Whether the signal lines are connected or not, simply applying VCC/GND will light up the LED. And it doesn't matter whether I use the ground pad, or the Vss pin.
I'm thinking of getting their demo panel and see how they did it.
Ok, got my reply from the manufacturer. Basically, that is the way this unit works and the explanation is, quote "The LED must be turned on when DycoLED is powered on. It’s because IC-on is always slower than led-on." Apparently if I send the 32-bit data initialize as all HIGH and stop the clock, it puts the LED in a virtual OFF state. Guess I'll just have to go try that.
