Hi Mark,
Yes there is a Cortex M0 Family processor involved in my project, it is used to compute some operation and give out the right resistor value by setting the value via SPI.
I've implemented a simple firmware, where i can interact via 3v3 UART for setting the right value of the digi-pot.
Also i've saved into uC 20 decimal value (0-256 range) for simulating the step from 30°C to 40°C (step 0.5°), the right value is saved into uC after a calibration made by measuring the resistence with the Ohmmeter.
The SPI value is sent correctly from uC to AD8400 (verified with a Protocol Analyzer).
My temperature operating range is from 25°C to 35°C.
Thanks
David