I have the following problem. ADC is working properly - the "Reading from the ADC" example works and I read back voltage values. Although I had to modify read_adc_voltage function call to have the correct number of arguments before the example would run.
The "Writing to DAC" example does not work. I do not see a square wave on the DAC output. Very occasionally the output does switch to 1.5V but then remains there. Are correct parameters being passed to spidev for the MCP4822E chip?
I have checked SPI clock, data and SC lines with an oscilloscope and everything seems in order. Perhaps the wrong SPI mode is selected?