Xmega = 64A3U-AU
I posted about this problem before: http://8515.avrfreaks.net/index....
I thought I had everything figured out but I was wrong.
I have done many tests to ensure that the autocalibration is working and that its source is the external crystal.
I have tried adjusting DFLL comp registers, DFLL Cal registers and also the value in the PER register. Nothing seems to help. I have spent hours, no make that days fighting with this. I am using the 1 second pulse from a GPS module. I have then run it and checked which register settings give me the most accurate time.For example it ran for 24 minutes and went out by about 16ms which was fine for my application. I then used that value in the comp register and ran it and compared the time with 2 stop watches. After about 30 minutes it was more than a second out. The external watch crystal has a fairly constant frequency of 32770. The DFLL seems to cause the 32Mhz to drift over time. All suggestions are welcome