I'm using an Arduino Uno Rev3 Board and need to send a trigger signal at a certain frequency (20-50Hz). This trigger signal should be as accurate as possible (+/- 0.01 ms). The Arduino site states that the arduino uno has a 16MHz Quartz Crystal, but I'm measuring a frequency accuracy of about 0.35% (which would be typical for a ceramic resonator) instead of what i could expect from a quartz (0.001%). I'm using the micros() function to measure time. Am I doing something wrong? How is my frequency so inaccurate?
Thanks for your help! :)
Edit: Indeed when I have a look at the schematics, I see the ceramic resonator (Blue circle). However, there seems to be another 16 MHz part (red circle). could that be a quartz oscillator?