So, you haven’t seen an update out of me in a while. This is because I’ve been struggling over the past week with getting my clock to return accurate, or at least consistently inaccurate results.
My test method was to use a little program that I wrote that would give me a 10 second count down before starting a timer that increments the LEDs once per minute. The idea was to use the 10 seconds to synchronize the timer with a timer known to be accurate and then let it run for a few hours and see how far off the minute mark it was. Take the number of seconds it’s off, divide by total number of seconds elapsed, and multiply by 1 million to get the parts per million (ppm) accuracy.
See, every crystal oscillator needs to be “tuned” with some Load Capacitors. I tried my best to match the Load Caps to the 22pF rating on the crystal’s spec sheet (even taking into account the parasitic capacitance on the breadboard), but I still couldn’t get good results.
