DAC control using a serial (USB) terminal. inplemented using Arduino libraries. Tried this on Adafruit SAMD21 QT PY and Seeeduino Xiao. Additional offset correction is implemented to allow for very accurate DAC output.
Three ranges are defined by REGION1_LIMIT and REGION2_LIMIT. OFFSET1_ADJUST is for voltages from 0.0V to REGION1_LIMIT, OFFSET2_ADJUST is for voltages greater than REGION1_LIMIT and less than REGION2_LIMIT. OFFSET3_ADJUST is for voltages above REGION2_LIMIT. The offset adjustments are numbers of LSB to add (or subtract if specified negative).
The "samd21_unique_id" function is used to get a SAMD21's unique ID so that different offsets can be used.
arduino_dac.uf2 works on the SAMD21 QT PY and Seeeduino Xiao boards. It will use zero offsets as your unique_id will not match the two that are hard-coded (they are my parts).