James Newton wrote: > I'm also curious about this, since one of our products uses the same sort > of > LED. > > But I'm also not sure I understand what you are asking... At what RATE is > the flickering? Are you talking about a rate that is slow enough for the > human eye to detect or at a rapid rate where they two colors blend (for a > person without color blindness) into a third color? Slow enough for the human eye to detect. 2 Hz or around there. The application is a brute-force method for figuring out which COM port the device is sitting on (in case the baud rate is set wrong). RTS driven by software toggles the red LED on/off, resulting in the rapidly changing yellow/green. BTW, I just realized that there is a mistake in my original post. Although there is another condition where the light changes from red to yellow, in this particular case, it's changing from yellow to green. My hope is that the brightness changes enough (2 LEDs on vs just one) to where the difference can be detected by color blind people. Vitaliy -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist