MCP7940.adjust() freezing in main loop

[StoneyStu]

Hello,

I'm finding that adjust() is working ok on initialisation in the setup() routine however I have a menu-driven date and time input system to allow the user to set their correct time. When I just use setTime() from the Arduino library it works (at least sets the time locally) however if I use the the MCP7940.adjust(DateTime) the system freezes. At the end of the menu input I have even hardcoded a value to see if I can get it to work: MCP7940.adjust(DateTime(2020,9,9,18,19,20)); but that has the same problem.

It is strange that during setup I can adjust the date to any hardcoded value using on the RTC but this doesn't help me allow the user to set their own date/time.

Any ideas would be appreciated, thanks, Stuart

[SV-Zanshin]

Let me dig up a MCP7940 to see if I can reproduce the problem. Which MCP are you using and on which Arduino processor (perhaps that might play a role in causing the problem).

[StoneyStu]

Hi,

I'm using an Arduino Micro so 32U4 processor and an MCP7940N RTC. My application also uses interrupts in the main loop to read a data line and I was wondering if that might be part of the problem.

Thanks for having a look at this.

Stuart

[SV-Zanshin]

I've got both of those (the Micro and MCP7940N) and will check it tonight. Any time when one programs with interrupts and experiences "hangs" there is a good chance that it is due to that. You might try to use the LED to show that the interrupt is being fired "(digital.write(!digital.read(13));" or use the LED in the MCP7940.adjust() code. I do seem to remember that I had some issues with the adjust() but can't remember if it was hanging or invalid values.

[StoneyStu]

Hi, Before you spend any more time on this, I think the freezing problem is solved. Although I claimed the adjust() was being called in the main loop, it was actually being called at the end of an ISR used to detect the last button press of a time/date set menu function. Of course an ISR isn't the place for this call, and it now seems to work using a flag so that the function invoked back the main loop to set the time/date on the 7940. Will do some more testing but I think it's now ok. thanks for your help.

[SV-Zanshin]

I've got a non-Micro Arduino setup with the MCP7940N and used multiple calls to adjust() with no problems, so I think that you've most likely found the problem. I'll close this issue but don't hesitate to open a new one if necessary.