1 2 Previous Next 16 Replies Latest reply on Jan 2, 2015 5:49 AM by waldemar.matejka

    ECG working but sometimes problem

    waldemar.matejka

      Hi

         

      I build ECG on CY8C27443 its working fine. But sometimes when I touch (knock) electrodes resets the processor. Program starts again. Attached schematic.

         

      Please help

        • 1. Re: ECG working but sometimes problem
          user_1377889

          Check for broken trace or bad solder on xres, Vcc and GND.

             

           

             

          Bob

          • 2. Re: ECG working but sometimes problem
            user_14586677

            Static certainly a common cause.

               

             

               

            If you have a DSO set it up for signals that meet something like this    Vsspsoc - .5 > Vsig or Vsig > Vddposc + .5

               

            and see if you can get triggers. Trigger mode set for normal mode, one of the prior mentioned levels. If

               

            you do have triggers then you have problems with coupling to that pin. Generally ground bounce or capacitive

               

            coupling will be root cause.

               

             

               

            You have  a charge pump on board, hence a lot of noise generated. Make sure your board layout joins its

               

            grounds close to power entry on the PCB.

               

             

               

            Use your DSO on infinite persistence, and look at supply rails while running and when touching

               

            electrodes. See if you can capture any large spikes.

             

               

            I do not see a .01 uF ceramic disc on output of regulator. That should be close to PSOC Vdd pin.

               

            Also the bulk cap ( 1 uF) on output of regulator should be close to PSOC Vdd pin, and not far from

               

            regulator pin. Read regulator datasheet to make sure you do not have to meet a min ESR for the

               

            bulk cap. Otherwise if it does have this constraint you could have high f oscillations on output

               

            of reg. I also do not see bypassing around the IA. Look at its datasheet for recommendations.

               

            Do not scrimp on bypassing, caps are your friends, generally speaking, concerning power domains.

               

            For bulk caps polymer tants best in class. There ESR vs f curves an order of magnitude better than

               

            standard tants.

               

             

               

            Board layout  is important to insure ground bounce and noise. Some ap notes attached. They are

               

            not PSOC 1 specific, but principles apply.

               

             

               

            Regards, Dana.

            • 3. Re: ECG working but sometimes problem
              user_14586677

              Another area of concern.

                 

               

                 

              You have C4, 4.7 uF, connected in series with IC5A input. You

                 

              need to check that if power is lost this cap cannot damage the

                 

              + input circuits of IC5A by discharging thru them, I would file a

                 

              issue with Analog Devices to get their opinion on that. Show

                 

              them schematic and ask about AD623 as well. Less concern

                 

              there because parastic structures in output generally can handle

                 

              issues like this, but ask.

                 

               

                 

              I found this in datasheet, see below.

                 

               

                 

              Lastly this cap represents significant C load on IA output, you need

                 

              to look at its phase margin on IAs AC response. Use A/D spice model

                 

              or hand calc this.

                 

               

                 

              And one final. Make sure the charge pump powers up after everything else.

                 

              eg pay attention to required power supply sequencing issues. Like when you

                 

              yank the battery on the linear reg, will the charge pump cause any issues

                 

              elsewhere in design.

                 

               

                 

              Regards, Dana.

                 

               

                 

               

              • 4. Re: ECG working but sometimes problem
                waldemar.matejka

                Thanks so much for your help.

                   

                Tomorrow i will have oscilloscope and i check everyfing.
                I will write a response.

                   

                 

                   

                Regards

                   

                Waldi

                • 5. Re: ECG working but sometimes problem
                  waldemar.matejka

                  I improved schematic. I add capiciators in suplly circuit and C4 for highpass is smaller.

                     

                  I observed on the oscilloscope, when modul BLuetooth HC-05 is connected, supply voltage fluctuates from 4,5V to 5V.

                     

                  I think, I demaged PSoC. I can upload program to processor and its all ok. But I dont have any feedback. UARTdoesn't work. Pins doesn't have high state.

                     

                  Regards

                     

                  Waldi

                  • 6. Re: ECG working but sometimes problem
                    user_1377889

                    Write a testprogram that uses a PWM connected to some I/Os to check pins working.

                       

                    By the way: There are brand-new Bluetoth Low Energy chips from Cypress, get a development kit here secure.cypress.com/

                       

                     

                       

                    Bob

                    • 7. Re: ECG working but sometimes problem
                      user_14586677

                      If you are seeing 1/2 a volt of noise on Vdd of PSOC thats a little too

                         

                      high, indicates bypassing not effective. Too small bulk cap and .01 uF

                         

                      ceramic disk not close enough to Vdd pin. Typical noise on Vdd should

                         

                      be < 200 mV.

                         

                       

                         

                      Post your schematic and project archive for us to take a look at.

                         

                       

                         

                          

                         

                                

                         

                      “File”                                                           Designer

                         

                      “Archive Project”

                         

                       

                         

                      Regards, Dana.

                      • 8. Re: ECG working but sometimes problem
                        waldemar.matejka

                        PWM doesn't work. I will buy new PsoC and I check.

                           

                        I don't have any capiciator close to pin uC. What

                           

                        What should be the capacitance of the capacitor next to the uC?

                           

                         

                           

                        Regard

                           

                        Waldi

                        • 9. Re: ECG working but sometimes problem
                          user_14586677

                          A "standard" would be .01 uF ceramic disk and a 10 uF

                             

                          polymer tantalum close to PSOC power pin.

                             

                           

                             

                          Regards, Dana.

                          • 10. Re: ECG working but sometimes problem
                            waldemar.matejka

                            Hi

                               

                            When I add polymer tantalum capiciator 10uF close to PsoC a can't togle power suplly in PSoC MiniProg. And doesn't work progamming with another suplly. What wrong ?

                               

                             

                               

                            Regard

                               

                            Waldi

                            • 11. Re: ECG working but sometimes problem
                              user_14586677

                              Not sure.

                                 

                               

                                 

                              When using Miniprog in power cycle mode the board cannot have any other source

                                 

                              of power.

                                 

                               

                                 

                              1) Using your scope do a single sweep capture on Vdd, trigger set to say ~ 100 mV, and toggle

                                 

                              Miniprog to see what start up looks like when Miniprog trys to turn on power to PSOC.

                                 

                               

                                 

                              2) Double check you 10 uF polymer is not installed reverse polarity.

                                 

                               

                                 

                              3) Using a DVM and a bench power supply, and measure the Vdd current. Checking for shorts.

                                 

                              Feel PSOC with your finger to see if its hot.

                                 

                               

                                 

                              4) Your board meets the following - (from Miniprog user guide)

                                 

                               

                                 

                              5) The MCP1702, if no battery installed, its output will not sink current, right ? Check this in datasheet.

                                 

                               

                                 

                              3.5.1 Programming Characteristics

                                 


                              Depending on the programmer capabilities, you can select various protocols. Some programmers
                              are single protocols, but others allow you to select different protocols. The Device Family and
                              Device drop-down menus adjust according to the protocol selected and the device to be pro
                              grammed. It supports the ISSP protocol.

                                 


                              Voltage supplied by MiniProg1 to target board is 5 V and total current supplied by MiniProg1 to the
                              target board being programmed is 302 mA.

                                 


                              Note Total current supplied to MiniProg1 from the USB port is 500 mA, current consumption is
                              198 mA. Hence, total current supplied to the target board is 302 mA (difference between total current
                              supplied and current consumption)


                                 

                               

                                 

                              Regards, Dana.

                              • 12. Re: ECG working but sometimes problem
                                waldemar.matejka

                                Thanks for replay

                                   

                                I check connection, polarity and its all right.

                                   

                                It working without capiciator 10uF. I think this is too large capacity.

                                   

                                Actualy a have only screen from scopemeter.

                                   

                                Regards

                                • 13. Re: ECG working but sometimes problem
                                  user_14586677

                                  It may be the polymer has such low ESR that it triggers short

                                     

                                  circuit protection in Miniprog. I will file a CASE on this to see what

                                     

                                  Cypress has to say.

                                     

                                   

                                     

                                  I did find another limitation, for SCL, SDA lines be < 30 pF C loading.

                                     

                                   

                                     

                                  Regards, Dana.,

                                  • 14. Re: ECG working but sometimes problem
                                    waldemar.matejka

                                    I found the cause of the error.

                                       

                                    Programmer caused an error.

                                       

                                    Every time during programing i have

                                       

                                    Program Finished at 21:52:34
                                    Verification of "Protect Area" is FAILED!
                                    Programming Terminated
                                    ===> Protect Failed
                                    Doing Protect
                                    Programming Succeeded
                                    Programming Starting
                                    Erase Succeeded
                                     

                                       

                                    But before update PSoC Programmer i don't have problem with that. Actually i have PSoC MiniProg and PSoC Programmer 3.22.0.

                                       

                                    What is wrong?

                                       

                                    Regards

                                       

                                    Waldi

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