i've found that the DACIFB offset calibration register OCR does not work correct for UC3(C).
While working on the DAC calibration function i found out that i was not able to get a DAC output lower than approx. 40mV (reference 3,3V VDDANA).
I then tried to set different offset calibration values by hand and found this:
- OCR values lower between -209 and 0 increase the offset.
- OCR values below -209 or above 0 do not change anything, offset doesn't get smaller.
So i guess the data format is not really 9bit with sign as described in the datasheet but 8 bit with an additional sign bit as 9th bit. This is a bit irritating but i can live with it.
Whatever i tried i found no way to get the offset below 40mV since configuring positive values (i've tested the full range between 0 and 0xFF) do not change the offset. So the offset mechanism looks broken in one direction.
Has anyone worked with the UC3 DAC and want's to share the experience?
Did yu manage to calibrate the offset and how?