5 Replies Latest reply on Dec 21, 2010 5:36 AM by hossam.fadeel

    RFID 125KHz reader, analog filter, amplitude demodulation

              Is any way to use PSoC3 analog blocks to make low frequency 125KHz RFID reader.   
      I try make RFID reader project for CY8C3444LTI-110 device, but I can't find analog LPF filter (exist only digital filter) or modulator.   
      Do you have any ideas?   
      Best regards   
        • 1. Re: RFID 125KHz reader, analog filter, amplitude demodulation
                  Hi Zbigniew,   
          PSoc3 has 4 general-purpose OpAmps which can be routed to pins via low resistance paths. These are intended to implement filters (Sallen-Key, etc) using external R/C components. The Beta Creator currently doesn't support filters using the SC/CT OpAmps (only PGA and TIA at present).   
          I'm not aware of anyone porting the 125 KHz RFID to PSoC3 yet, although it shouldn't be too difficult to implement on PSoC3.   
          Rick Flores   
          • 2. Re: RFID 125KHz reader, analog filter, amplitude demodulation
                    Hi rwf,   
            Of course your solution are correct, but I going to use CY8C3444LTI-110 chip. It has only 2 OpAmps, First I used for PGA, second for Vdda/2 buffering, so I ask about SC filters.   
            I change my circuit, and use second OpAmp for LPF and add some passive components.   
            When we are going to support SC filters using the SC/CT OpAmps?   
            Best regards   
            Zbigniew Kuczbanski   
            • 3. Re: RFID 125KHz reader, analog filter, amplitude demodulation
                      Hi Zbigiew,   
              The CY8C34 family should have 2 "uncommitted" opamps AND 2 SC/CT opampsitted" opamps.   
              A SC/CT block would typically be used as PGA (that's what the PGA Component uses).   
              For a Vdda/2 buffer, you could use either the second SC/CT opamp or an "uncommitted" opamp (the difference being that an uncommitted opamp is a more direct connection if you stick to its "preferred" pins).   
              As to when Creator will get SC/CT filters, I'll ask and post the answer I get. If you're really dedicated eager, you can access the "Analog Primitive" Components, They can be exposed via Tools/Options/DesignEntry/ComponentCatalog/ShowHiddenComponents. The SCBlock is there, however there is no data sheet, so you would need to dive into the TRM to figure-out how to use it. I know others have noted the lack of PSoC3 SC filters, but I don't know how vocal they are.   
              If you're looking for a single-poll RC low pass filter, there's a "LPF" component in the Analog Primitives (see section 32.4.6 in 001-50235 TRM). Basically you get a low pass filter made from a combination of {5,10} pF and {200K, 1M} Ohm, so with 1M/10pF you could get Fc = 16 KHz.   
              Hope this is somewhat helpful   
              • 4. Re: RFID 125KHz reader, analog filter, amplitude demodulation
                        Sadly they missed the cut for the next release. There is a lot of content development on our plate right now. These are planned for a service pack release fairly deep into 2010. Sorry the news is not better.   
                I'm taking note of these requests for content though so... if other readers have a need for SC filters please post a comment here. The more justification arguments you make the better. We're open to reviewing our roadmap if we get clear messages that we're wrong!   
                -- yfs