[Edit: Note the frequency may be 9.5MHz instead of 19MHz]
I have a Nano i have been using today for some tests on i/o pulse timing. I was looking for specific timing so i decided to do a few measurements.
What was surprising, to say the least, was that two different tests i had performed seem to show that the crystal or whatever is used on this board to generate the clock frequency for the CPU must be around 19MHz not 16MHz. Is this even possible?
The first measurement was with a timing program that outputs a 250kHz square wave pulse. i have read other posts on this site that specify the timing when using the PORTB= instruction and PORTB|=B00100000 and the like, and have inserted several of these instructions that create a high and low signal which when measured on digital pin 13 measures really close to 250kHz. In fact, on two different meters it reads 250.0kHz. On the CRT scope (old guy) it measures close to 250kHz but the time axis is not that accurate so i trust the meter readings more in this case, although the scope should not be off by more than about 10 percent, plus or minus.
The second measurement was using a short wave radio which quiets very noticeably when the radio is tuned to exactly 19.005MHz and stays a little quiet at 19.010MHz, but does not quiet anywhere near 16MHz as my Nano does. My Nano was quiet at 15.800MHz or something like that, which is understandable, but 19MHz seems way too far off.
Could it be that the manufacturer (probably Chinese) put in the wrong crystal or resonator?
Also, would the serial communications still work even if the crystal was the wrong frequency?