4 Replies Latest reply on Oct 15, 2011 1:38 AM by pmad

    Error in ADC readings

    koushilya.g

      Hi,

         

      I am using an ADCINCVR to measure an input signal of 0-5V.  I am able to get the ADC working, but am observing high amount of error in the ADC readings.  What could be the possible reasons for the error?

         

      Thanks in advance for any leads.

        • 1. Re: Error in ADC readings
          pmad

          Well your question need more details that what kind of error you are facing. May be these points will help you in locating the kind of error and its root cause:

             

           

             

          1. Make sure that the analog column clock does not exceed the maximum column clock frequency for ADCINCVR.

             

          2. Clock for both Analog and Digital blocks should always be equal. If you are using the latest version of PSoC Designer then this is automatically taken care of.

             

          3. Make sure the calc time is properly calculated based on you data clock settings.

             

          4. Make sure you have done the correct setting for Analog Power from Global Parameters. For ADC to work properly, it should never be set to SC Off or All Off.

             

          5. If you are getting offset errors then you can use CDS method to remove them. Refer to App note AN2226 for more details.

             

           

             

          For more details about ADC, there is a wonderful blog available on CY website. You can follow the same by following link: http://www.cypress.com/?rID=39197

             

           

             

          Best regards,

             

          Pushek

          • 2. Re: Error in ADC readings
            koushilya.g

            Thank you for the quick response, Pushek.  The problem was with the analog power setting.  I had the ADC's running at High Power, but had set the analog power to SC On / Ref Low.  I changed this to SC On / Ref High and this solved the problem.

            Regards,
            Koushi

            • 3. Re: Error in ADC readings
              philip.nielsen

              I was using the ADCINCVR and I saw some errors. I needed to read x.xxx volts. The third place was for milivolts of 0. At 5 volts in I was getting around 50 MV offset. I checked the datasheet and it stated .1% full scale. So 5 volts X .01 = 50 MV. Am I correct?

                 

              If so then is there any SPI code examples for me to look at. I am in a crunch to get a new ADC on my pc board ASAP. I have found external ADC ICS. But the interface is SPI. I have spent most of the day tring to find examples for SPI code for Cypress. Most of the code has been written for the PIC,Atmega and Andruion.

                 

               

                 

              Ant help would be appreciated.

              • 4. Re: Error in ADC readings
                pmad

                 Yes, your understanding is correct but there are various ways to completely remove the effect of Offset voltage in firmware. Please refer to the application note available at the following link: http://www.cypress.com/?rID=2894

                   

                 

                   

                This is explained via Video, Application Note and Example Project.

                   

                 

                   

                Best regards,

                   

                Pushek