Guru
Joined: 11/12/2012
Location: United KingdomPosts: 10671
| Posted: 07:48am 04 Jul 2024 |
Grogster has also reported some boards not starting up properly and has sent me an example to diagnose.
The issue seems to be the RTC crystal circuit.
The crystal is 12.5pf and the two load capacitors C54 and C55 are specced at 10pf
This should give 5pf for the capacitors in series and allow 7pf for the board to give a reasonable match to the crystal.
Perhaps the capacitors supplied by JLC are incorrect? I can’t measure anything that low so no way to test.
I have fixed Grogster's board by simply removing C54 and C55 so if anyone else is having a problem they could try that.
There is an alternative fix with new firmware that clocks the RTC off the main 8MHz oscillator which is more accurate and eliminates the need for the RTC crystal entirely.
HOWEVER, the oscillator doesn’t run when the power is off so the DS3231 has to be enabled to avoid time loss with this firmware.
I can post this firmware if necessary.