Arduini Pro Mini SCL and SDA Pins Don't Work

Hey guys,

I am using a DS3231 RTC to program an arduino pro mini to sleep and wake up at given points in time. I was able to get this working using a mini I had lying around but when I soldered the RTC to the mini (SCL to A5, SDA to A4, ground to ground and no 5v since I have a battery in the rtc) I’m using for my project, I was unable to get the two to communicate with each other. I run an I2C test sketch and it didn’t detect the rtc. When I tried it with a new rtc I bought, it just says “scanning” and nothing happens.
From this, I think the problem is that the SCL and SDA pins on the mini in my project don’t work. Is there anyway way I can test whether this is actually my problem?
If it does turn out that the I2C pins aren’t working, would I be able to use different pins for I2C rather then have to transfer everything over to a new mini board? I have heard that is is slow/not ideal but since I’m only using the clock for interrupts (so the only I2C communication is to reset the alarms) would this be alright?

TLDR; How to test if arduino pro mini SCL and SDA pins are working properly, and can you use other pins for SDA and SCL?

Thanks in advance, and sorry if I missed any info or wasn’t clear enough :slight_smile:

can you use other pins for SDA and SCL?

You can use a Software I2C library. This looks like a nice list of options:

How to test if arduino pro mini SCL and SDA pins are working properly

I’d guess the “pro” approach would be to use a logic analyzer to watch the communication between the Pro Mini and the DS3231 to get an idea of what is going on. Depending on the findings, an oscilloscopt might be useful to look at the signals.

Another option would be to connect the same DS3231 to another Pro Mini with the exact same wiring and run the same sketch on it. If the same device and same software work on one Pro Mini and not on the other, you know the problem is with the Pro Mini.

Ok, thanks. I think I'll take the easy approach and try using the DS3231 on my other pro mini. :slight_smile: