The RP235X LPOSC frequency may be out of whack with what it should be by +/-20% so, if using it as the clock source for the Always-On Timer, it needs to be calibrated, unless prepared to see gains or losses of up to 12 seconds per minute, 12 minutes per hour.
Fortunately the LPOSC frequency can be trimmed to get it within +/-1.5% of what it should be which should reduce the gains or losses to around 1 second per minute, 1 minute per hour. Not brilliant but not too bad, liveable with for many use cases, and an external RTC can be added if it isn't.
To calibrate I was thinking the best approach would be to set the Always-On Timer or some other timer to be clocked by LPOSC while another is clocked from XOSC; nudge the LPOSC trimming until it delivers the closest matching results for timer increments within some period.
Unfortunately I couldn't find any example code for doing such calibrating, nor any API which would do it for me.
I probably could plough through the documentation, figure out clock sources and related stuff, do it myself, but if anyone has already done this, or has a link to doing it, it would save me all that effort and I'd be very grateful.
Fortunately the LPOSC frequency can be trimmed to get it within +/-1.5% of what it should be which should reduce the gains or losses to around 1 second per minute, 1 minute per hour. Not brilliant but not too bad, liveable with for many use cases, and an external RTC can be added if it isn't.
To calibrate I was thinking the best approach would be to set the Always-On Timer or some other timer to be clocked by LPOSC while another is clocked from XOSC; nudge the LPOSC trimming until it delivers the closest matching results for timer increments within some period.
Unfortunately I couldn't find any example code for doing such calibrating, nor any API which would do it for me.
I probably could plough through the documentation, figure out clock sources and related stuff, do it myself, but if anyone has already done this, or has a link to doing it, it would save me all that effort and I'd be very grateful.
Statistics: Posted by hippy — Wed Nov 13, 2024 8:42 am