1.I read analogueWrite code in Arduino website, the frequency most of the pins is 490Hz, it is very slow?
"The frequency of the PWM signal on most pins is approximately 490 Hz. On the Uno and similar boards, pins 5 and 6 have a frequency of approximately 980 Hz. " From the Arduino website
2. It is really this? I though the Microcontroller could output big frequency like it's clock 16MHz,
the 16MHz is only for the program speed and the 490Hz for the output of the microcontroller frequency?