I'm using the Sparkfun DS3234 with the MKR1010 using RTC by Makuna version 2.3.5 on the Arduino IDE version 1.8.14. I found that I needed to comment out line 265 of the file
With this change, it works OK.
Possibly, this was somehow fixed in later versions.
I wanted to use the DS3234 module since I'm confident that the battery drain is very low - maybe the RTC in the MKR1010 is also, but I wasn't aware that a battery could be connected to it without powering the whole chip.
You tried to use two rtc code simultaneously, perhaps this lead to conflict. When you comment the line, you rid the original MKR board rtc code from the project and the rest works fine.
But I don't think this as bug in the MKR code, required to be fixed. This is specific to your project. It is expected that users will not add an external RTC if the board has a built-in.
It seemed like using the on-board 32kHz might be complicated since it isn’t obvious how to keep the clock ticking without maintaining power to the whole board. Possibly, this could be handled by putting lots of stuff into low power mode, but I suspect that this would take a lot of work. Since my application only needs to have the system turned on for short periods, I just put a power switch on the battery. I would be interested in being notified if anyone works out how to keep the RTC clock ticking in a very low power mode.
Another reason for the DS3234 is that I wanted a second crystal as a check on the time base since I’m measuring a flow rate for a medical application. I rely on the millisecond timer which I assume is driven by the 32kHz oscillator. The DS3234 is a fairly easy way to get this redundancy, although there are no doubt cheaper methods.
I find that the wifi transfer is pretty slow – possibly I’m not using it optimally and I’ll need to dig into this question since it apparently is capable of Mbit transfer rates. (I’m transferring a fair amount of data to a PC after collecting many records and storing them on a uSD.)
Kudos on your development of a very complete, compact and cost effective system! I’ll upload my project when I’ve finished documenting it.