I've been out of the loop for quite some time and there's not a lot of info online about these rgb headers. My motherboard doesn't have any rgb headers but I have a coolermaster masterair pro fan that comes with a standard 4-pin rgb connector. What is the pinout of these things and what type of signal is coming from a motherboard or rgb controller that controls the led?
It seems that the pinout is 12V-G-R-B. How is the brightness, hence color combination controlled? I assume it is most likely done through duty cycle/pwm but I can't see how it is done in a common anode config of the rgb header. Is the pwm signal supplied through the respective G, R, B pins? Does the fan motor and leds share a common cathode/ground through the 3 or 4 pin fan header?
Are the G-R-B pins connected to a low-side switching circuit on the motherboard or controller?