I have a DS3234 RTC wired up to an Uno and it all works fine using the 5V output from the Uno to the Vcc on the DS3234, using SPI natively (no library). The datasheet says typical voltage is 3.3v so I used that output from the Uno and I can set the time but it never increments and the interrupt doesn't work. All the clock functions only work on Vcc=5V.
I took out the Vcc and GND from the Uno and put the battery in and it's the same. Clock won't increment and interrupt doesn't work. It only works on 5V Vcc from Uno.
If I read the time in the loop it's all 0s. If I don't read the time, it's stuck at the time I set it to in setup.
Is there something I'm missing? I don't have pullup resistors in the circuit, just wires from chip to Uno. Are the wires too long? They are standard breadboard wires about 6in long.