19fd0a5587
When using HSE to clock RTC NuttX internal time is gaining 5.5 second per minute. Problem was NuttX using 7182 for one of the RTC division factors, it should have been 7812. The incorrect factors used are 7182 and 0xff. These are used in 3-4 places within Nuttx and other places as 7812 and 0xff. However, the STMicro app note AN4759 suggests using 7999 and 124, which is what I've used. Explanation: These 2 factors are used to divide the HSE clock (which at this point is 1 MHz) to 1 Hz for the RTC hardware. To test the 2 factors, add 1 to both numbers and multiply them together. The result needs to be as close as possible to 1 MHz. The suggested values of 7999 and 124 => 8000*125 = 1,000,000, the prime factors. So, the best fix for Nuttx would be these values. Issue discovered and fixed by Peter Moody |
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