I got myself a Diymore DS3231 RTC, plugged in CR2032 battery, and hooked it up to pins 20 and 21. When I ran a DS3231 sample, I got 2165-165-165 date and 165:165:85 time. I read several threads here, figured that it means that RTC is not communicating with the Due. Following thread recommendations, I tried removing RTC battery, adding plug-in power supply for the Due, and updated wire.cpp library, but nothing worked. I2C scanner was showing three devices though which I don't get:
I2C device found at address 0x57 !
I2C device found at address 0x5F !
I2C device found at address 0x68 !
I have an SD card hooked up to SPI, but nothing else besides RTC. Finally I plugged the RTC into SCL1 and SDA1. Now I2C scanner shows no devices found, but the RTC works fine, shows and keeps correct time:
2018/10/24 (Wednesday) 19:46:10
since midnight 1/1/1970 = 1540410370s = 17828d
now + 7d + 30s: 2018/11/1 8:16:16
I am really confused by this behavior. Any thoughts on what is going on here? Thanks! Igor