I am connecting the SPI bus pins of two development boards:
They are each connected to their own wall-wart power supplies. I have confirmed that the connected pins are all operating at 3.3v. However, I know that "3.3v" is only in reference to their own grounds.
Are there any potential risks to connecting the VDD (3.3v only) and ground pins between the boards to make sure the voltages match up correctly?