1 2 Previous Next 22 Replies Latest reply on Dec 19, 2013 6:59 PM by user_14586677

    ADC-DAC

    souleymane.gueye

       Hello,

         

      I'm a beginner on PSOC, and i'm trying to understand ADC et DAC components on PSOC Designer.
      Then i put a ADC and a DAC completely opposite for having the same input signal and output signal.
      But after doing all adjustement, I don't get the same signal.
      I need some help

        • 1. Re: ADC-DAC
          user_14586677

          If you set ADC resolution to same as DAC you will still have a small

             

          amout of error between the two readings. Are you comparing binary

             

          result from ADC or converting to V, same for DAC, then comparing ?

             

          You have to look at what the read returns on ADC, sign or unsigned,

             

          reference, and do the converison.

             

           

             

          Post your project archive and forum can take a look at it.

             

          "File", "Archive Project", do not use chrome to post.

             

           

             

          Regards, Dana.

          • 2. Re: ADC-DAC
            user_14586677

            One other contributing factor, if using PGA feeding ADC (from datasheet) -

               

             

               

            The input and output voltage ranges of the amplifier do not extend to the power supplies

               

            (i.e., they are not "rail-to-rail" opamps). The allowed input range is a combination of input

               

            limit, output limit, power supply voltage, analog ground value, and selected gain. This is

               

            illustrated in the DC and AC Electrical Characteristics section.

               

             

               

            Regards, Dana.

            • 3. Re: ADC-DAC
              user_14586677

              As an aside you posted in PSOC 3 forum, which uses Creator tool, not Designer.

                 

               

                 

              If you are in fact PSOC 3 then using ADC with input buffer disabled will give you R-R

                 

              performance. The PGA is R-R in PSOC 3, although allowed inpout swing dependent

                 

              on G you use.

                 

               

                 

              Regards, Dana.

              • 4. Re: ADC-DAC
                souleymane.gueye

                I think I have perfectly configure the PGA and the ADC.But I have some difficulties to configure the DAC, then i just have noise on DAC output.

                   

                Do you have  a few time for consulting my software andtell me exactly where i'm wrong or correct it?

                   

                PS:For the next time, where do you publish my answers?

                • 5. Re: ADC-DAC
                  user_14586677

                  "PS:For the next time, where do you publish my answers?"

                     

                   

                     

                  Stay with this thread for now.

                     

                   

                     

                  Go ahead and post project archive and Forum will take a look at it.

                     

                   

                     

                  Regards, Dana.

                  • 6. Re: ADC-DAC
                    souleymane.gueye

                     Here is the project.
                    Thank for your support

                    • 8. Re: ADC-DAC
                      user_14586677

                      The project you posted is incomplete. In Designer go to "File",

                         

                      "Archive Project", and post that zip file.

                         

                       

                         

                      Regards, Dana.

                      • 9. Re: ADC-DAC
                        souleymane.gueye

                        I hope there is the good one

                        • 10. Re: ADC-DAC
                          user_14586677

                          Justr started looking at project, change -

                             

                           

                             

                          1) Global properties, upper left window, A_Buff_Power, Op-Amp_Bias to high power.

                             

                           

                             

                          Regards, Dana.

                          • 11. Re: ADC-DAC
                            user_14586677

                            The DAC data value should be set to offset binary, as you have

                               

                            set the A/D to unsigned.

                               

                             

                               

                            You want to decimate by 32 to achieve 8 bits to match DAC, so

                               

                            set PulseWidth in CAN properties to ( 4*n -1 ), n = decimation rate,

                               

                            so set PulseWidth to 127.

                               

                             

                               

                            Global properties, set CPU_Clock to sysclk/1

                               

                             

                               

                            Regards, Dana.

                            • 12. Re: ADC-DAC
                              user_14586677

                              Change this line of code to -

                                 

                               

                                 

                                      if  ( CAN_fIsDataAvailable() > 0 ) {        // attente que la donnée issue du CNA soit prête
                               

                                 

                              Regards, Dana.

                              • 13. Re: ADC-DAC
                                user_14586677

                                Last change your global properties VC1 to a divisor of 8, so that you

                                   

                                can meet DAC max clock rates.

                                   

                                 

                                   

                                In general when you place a module, look at datasheet, it covers each

                                   

                                property.  Additionally it covers each API, what it does, and what it returns.

                                   

                                 

                                   

                                And global properties, always examine those to make sure you are set

                                   

                                up correctly. Same with analog column clocks, they must meet the clock

                                   

                                rate of modules in that column. Adjust VC1/VC2/VC3 for clock rates to compo-

                                   

                                nents that use them.

                                   

                                 

                                   

                                Regards, Dana.

                                • 14. Re: ADC-DAC
                                  souleymane.gueye

                                   I do all the changes you ask me to do (thank you by the way).But when I want to digitize at 40 kHZ, I just have noise.
                                  I think there is a problem with the clock of the DAC.

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