Arduino 2009 Crystal Clock Speed

Has the Arduino an exact clock speed at 16mhz (16.000.000) or something similar ?

Like 16.777.216 ?

Want do a atmega328 circuit on a breadboard.

What is the best crystal frequence to clock him ?

What is the best crystal frequence to clock him ?

Stick with a 16mhz crystal or 3 terminal ceramic resonator, otherwise you will have to modify some files in the Arduino IDE.


If you wanted to run the arduino environment with (say) an 8 Mhz crystal, what files would you need to modify and which lines to maintain sane millis(), delay() and serial port timing?

I want to run the Atmega328 at 3.3 volts and it looks like I will have to use a lower frequeny crystal.

16.777.216 Where did you get that number?

16 777 216 = 224.

This would be a great frequency to have (a little like watch crystals are typically 32.768kHz = 215), but no, it’s the decimal variety, not the close power-of-two.

NB, it is “MHz”, not “mHz” or “mhz”.
“mHz” is the correct way to write milli-Hertz, a measurement nine orders of magnitude smaller (aka “slower”) than mega-Hertz.