I have an Arduino Uno clone that I purchased to start learning.
Installed ok, and I uploaded my first sketch fine.
The sketch is a 24hs countown timer, available here:
Everything was looking good until I noticed the seconds felt a little slower, so I compared with a real clock, and yes, it was a lot slower. The arduino took 750 seconds to count 600 real seconds (1.25 slower) I realized that it was the exact difference between 20Mhz and 16Mhz (20/16=1.25)
So I moved the Atmega328p with the code to a breadboard and I installed a 20Mhz crystal, and the countdown started working fine.
I would like to know what is wrong.
Maybe the fuses are set for 20Mhz but the resonator installed is 16Mhz? that would explain this?
Or it has to do with the bootloader?
I want to know if I can correct this. The resonator on the board is very small, it would be very difficult to replace with a 20mhz part as I did in the breadboard.