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K22F analog reads

Question asked by stephen hibbs on Mar 19, 2016
Latest reply on Mar 29, 2016 by stephen hibbs

Hello, I am having trouble performing analog reads with the K22F board. I am running adc_lptmr_trigger_frdmk22f example project, and modifying the pin selection within there, using KSDK 1.2, in kinetis design studio 3 on a Mac.

  1. The results are good for ADC0_SE23 and ADC0_SE8
  2. I have not been able to get it working for ADC0_SE21, ADC0_SE7b, ADC0_SE22. Have been selecting the pins via the ADC_INPUT_CHAN variable. The ADCH bits are being set properly, and I have scoped the pin to see that the desired signal is indeed reaching it. However I get output that is essentially pin noise.
  3. Using single ended reads (differential reads give all low)
  4. I can confirm that the pins are set to default/analog in the mux registers
  5. I have tried with ADC_INST as 0 and 1


I have spent a few hours on this trying different variations of registers and reading around on this forum, but so far I have had no luck getting it working. Is there something I'm missing here?