4 Replies Latest reply on Jan 5, 2018 8:34 AM by rlos

    ADC returns positive limit everytime

    kjgregory83_2308861

      I've been developing an embedded system for some time using the CyBle-143A development kit on a custom carrier card. Among other things, the systems uses the SAR ADC to take some measurements at a relatively low rate. So far this has worked to my satisfaction.

       

      I just received our new full custom card with the same PSoC4 device on it (CY8C4248LQI-BL583). The hardware on the new PCB is nearly identical to the old platform we merged the schematics for the CyBle-143A kit with our carrier card schematic to eliminate the connectors to reduce manufacturing cost. I loaded the same code on the new card and every other function appears to work except the ADC always returns the maximum value (0xFFFF). One small difference between the old and new cards is that I omitted the 1uF bypass cap on the VREF pin for the new card but documentation seems to indicate that this is optional. I checked the voltage on the ADC input pin (P4.0) and it's nominally close to zero.

       

      Below shows how the ADC is configured. In my code, I initialize the ADC using 'ADC_Start()' and I read it periodically using 'ADC_GetResult16(0)'.

       

      What could be some reasons for getting these results? What are some things I can check to debug this issue?