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DAC voltage reference on TWR-K64

Question asked by Andy Berger on Jan 17, 2018
Latest reply on Feb 12, 2018 by Kerry Zhou

The K64 Reference manual states that the onboard 12-bit DACs on the TWR-K64F120M can be set to use DACREF_1 or DACREF_2. Where do I choose the voltages that determine DACREF_1 and DACREF_2?

 

Using jumper J29, I am able to choose V_BRD as:

  • 1-2: 3.3 V from K20 (default)
  • 3-4: 3.3 V from K64
  • 5-6: 3.3 V from regulator
  • 7-8: 1.8 V from regulator

 

But regardless of the jumper setting I use, setting the DACREF to 1 vs. 2 in software has little effect on the maximum DAC output. That is, if I use jumper setting 1-2, I get about 3.3 V out regardless of whether I set the DAC reference to DACREF_1 or DACREF_2 in software. And for jumper setting 7-8, I get about 1.8 V regardless of the software setting. Is there a way to independently set DACREF_1 and DACREF_2?

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