1 2 Previous Next 28 Replies Latest reply on Nov 26, 2012 2:38 PM by dakn_263916 Go to original post
      • 15. Re: ADC problem
        userc_38487

        Have you tried with ADC Continuous mode of operation ?

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        • 16. Re: ADC problem
          helic_263931

          I think the TextLCD is not asynchronous. All write commands wait until the LCD is ready. This means that it will slow down the loop to accomodate the LCD speed. But writing so fast means you cannot really ready anything on it...

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          • 17. Re: ADC problem
            dakn_263916

            I should have been more explicit on what is asynch and what is not.

               

             

               

            The 44780 Controller has a busy flag which is the basis of handshake for writes/reads of commands or data. Hence that is a synch interface.

               

             

               

            What is asynch is the relationship of what is written and when it gets to actual LCD segments, due to an internal controller that is not synced to MPU clock in any fashion. It is possible to write at a rate where one or more internal ram buffer characters does not always get displayed one for one. That is the display self refreshes at its own frame rate, not knowledgeable about how often the data in any given ram location has changed. In other words the controller is dumb, it has no knowledge of what, when, data has changed in the frame buffer. It just simply regurgitates it mindlessly to the segment lines, this then is asynch behavior to the output.

               

             

               

            Regards, Dana.
             

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            • 18. Re: ADC problem
              userc_42486

              here i am uploading complete work , in which the final output is display of voltage which corresponds to particular glucose level.

                 

              test strip interface to psoc:

                 

              1) pin 1 refers to working electrode

                 

              2) pin 4 refers to reference  electrode

                 

              3) pin 3 refers to central electrode

                 

              here the default output i am getting is 3.17v but after applying blood to the test strip output voltage going to 0.18v which should not happen.

                 

              where i am going wrong , how to correct it can anybody help me in this regard.

                 

              thanks

                 

              prp

              • 19. Re: ADC problem
                dakn_263916

                If no test strip is attachedPin_1 floating, you should have

                   

                 

                   

                1) 400 mV at output of TIA

                   

                2) 3.2 V at output of PGA

                   

                 

                   

                This should also be true if you attach test stip with no solution ? I am not an expert

                   

                on test strip parameterics.

                   

                 

                   

                If test strip goes to .18 V Then TIA out should be 22.5 mV, Vout = 22.5 mV = Vref - 40 x Intia,

                   

                so Intia (uA) = ( 400 mV - 22.5 ) / 40 =~ 9.4 uA

                   

                 

                   

                Is this the current you think you should have ?

                   

                 

                   

                This shows for 100 mV ref time response of current, does this jive with your time response scaled

                   

                by your ref voltage ?

                   

                 

                   

                      http://electrochem.cwru.edu/encycl/art-g01-glucose.htm

                   

                 

                   

                Regards, Dana.

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                • 20. Re: ADC problem
                  dakn_263916

                  Some reference material -

                     

                   

                     

                  Regards, Dana.

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                  • 21. Re: ADC problem
                    userc_40557

                    this might help you out in designing of blood glucose meter

                       

                    http://www.cypress.com/?rid=43661

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                    • 22. Re: ADC problem
                      dakn_263916

                      I do not see in your code the drop trigger so that you can generate

                         

                      the v(t) response as shown ?

                         

                       

                         

                      file:///C:/Users/Dana/Documents/1%20Cypress/Ap%20Notes/Blood%20Glucose/Electrochemistry%20Encyclopedia%20--%20Electrochemical%20blood%20glucose%20test.htm

                         

                       

                         

                       

                         

                       

                         

                      Regards, Dana.

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                      • 23. Re: ADC problem
                        userc_42486

                         i didnt understand what is drop trigger?

                        • 24. Re: ADC problem
                          dakn_263916

                          If you look at the reference material you see a time response

                             

                          of the drop coming into contact with the sensor, as shown in

                             

                          this graph. Then an exponential decay as the chemistry of the

                             

                          reaction proceeds. This reference discusses timing of when to

                             

                          take your measurement. So you have to time your A/D measure-

                             

                          ment after you detect the contact of the drop. Discussed in the

                             

                          various ref material I have sent you.

                             

                           

                             

                                http://electrochem.cwru.edu/encycl/art-g01-glucose.htm

                             

                           

                             

                           

                             

                          Regards, Dana.

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                          • 25. Re: ADC problem
                            dakn_263916

                            You can always consider a peak detector to capture the max

                               

                            value of the response, then digitizing its output, then resetting

                               

                            it for the next use.

                               

                             

                               

                            Regards, Dana.

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                            • 26. Re: ADC problem
                              userc_42486

                               here if using peak detector, voltage levels are scaling down i.e if the input to peak detector is 0 to 4 to 0 . the output should be 4v but the output of peak detector is scaling down to millivolts which is not true.how to over this problem?

                                 

                              Thanks

                                 

                              PRP

                              • 27. Re: ADC problem
                                userc_42486

                                 here using peak detector, voltage levels are scaling down i.e if the input to peak detector is 0 to 4 to 0 . the output should be 4v but the output of peak detector is scaling down to millivolts which is not true.how to over this problem?

                                   

                                Thanks

                                   

                                PRP

                                • 28. Re: ADC problem
                                  dakn_263916

                                  If you look at response time to peak all peaks oocur ~ 1 sec, your A/D is running

                                     

                                  much faster than that, so easiest method is running the A/D continuously and do the

                                     

                                  peak detection in software.

                                     

                                  If you use an analog peak detection method thats basically stored charge on

                                     

                                  a capacitor subject to discharge via leakage currents. You can calculate droop

                                     

                                  on a capacitor Q = C x V, I = C dV/dT, dV = ( I x dT ) / C

                                     

                                       www.cypress.com/?docID=38360

                                     


                                  Regards, Dana.

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