4 Replies Latest reply on Apr 25, 2012 3:45 PM by JoMe_264151

    Queation about PRS again!

      Dear Bob,


      I am first in this Community and know that this community will be helpful for our research members.


      The man who asked a question about PRS is my research member. After I read your advice, you need more detail information about our problems.


      Until now we have developed for the EMR(electromagnetic resonance) tablet device with Psoc3. In the system, in order to drive the coil to emit electromagnetic power from coil to pen(LC circuit) like a  wireless power transmittion, we used PWM signal frequency pulse. After driving PWM pulse to coil driver, the response voltage signal of drive coil shows sine wave.


      But this driving condition has some problems because the pen LC condition( or resonance frequency) changed due to some reasons but we don't know the exact resonance frequency. Under this conditon, we have to transmit maximum power to pen. To overcome this problem, we decided that if we send broad band waveform(from 450KHz to 500KHz) such as pseudo random pulse,we can send more energy under miss match between the driving frequency and  pen natural frequency. I think if we understand more about Pseudo random pulse generation configuration, we can make such signal.


      So I ask for followings if you can support,


      1. More examples to control PRS


      2. if PRS does not support our problems, I think we can make bit stream like a PRS by using shift register ways. Is there any case study about making bit stream by using predefined user data.


      ps. The harmonic composent of PRS signal is not important becase only fundamental frequency is transmitted to pen due to analog circuit ie the square wave changed into sine wave.

        • 1. Re: Queation about PRS again!

          In addition, we want to generation the pulse stream with finite number of pulse not infinite pulse stream.


          Thank you!

          • 2. Re: Queation about PRS again!

            What I understand from your post PRS is not what you can use for solving your problem


            At a resonance-point normally something happens within a circuit that can be measured. Is there a chance of a "calibration"?Within the PSoC3 are ADCs to measure voltages or even small currents, you may program a peak-detector and so on. So there might be a chance to measure the actual resonant frequency or even use a closed-loop to control it.


            You can sweep the frequency of a digital signal under CPU-control, there are examples for oscillators, VCOs to find here. Try the keyword search in the upper right corner.




            But that all depends on your electronic design, so you'll have to check and discuss that.




            regards, Bob

            • 3. Re: Queation about PRS again!

              Thank you for your fast response.


              My opinion is as follows;


              Because of our know-how, I cannot describe more detail about our device operation process.


              But in normal consumer device, the function such as spectrum analyzer is not possible to employed in source code.


              And the function to measure the spectrum of input signal is out of scope for comsumer device.


              Because of my limited english description, I cannot describe more detail. That is problem to solve this problem.


              I explain more detail.


              The electric pen is composed of L and C and  the natural frequency can be change from 450KHz to 500KHz due to some reason(Sorry!). But the goal is to detect the natural frequenct of pen. The thechnology to detect the natural frequenct in real time  already we can do.  To detect the natural frequency that is changed very fast, we have to excit the pen that means to give a power to excit the pen. Because of we don't know the natural frequency of pen, we have to give the power frequency from 450KHz to 500KHz(the natural frequency range of pen) but the sweep the frequency is too slow to detect in real time system. To overcome this problems, if we give power such as random signal but these frequency from 450KHz to 500KHz, we can exit the pen more eficiently and fast and get information more fast. As you know well, in capacitance touch technology of cypress used the preudo random signal to detect the capacitance information very fast. Like this application, we want to use the pseudo random signal as a excitation source.


              Is there any way to make PRS which has a fundamental frequency band from 450KHz to 500KHz? I think if I understand the PSOC3's PRS generater's principle, I can employ the PRS on my Tablet system. Unfortunately, I have no basic knowledge about How to generate PRS signal with microprocessor.


              or Is there any way to generate the square wave signal by using pre-made data in real time? If this is possible, from lots of try to make PRS we want, we can employ our idea by using PSOC3.


              Thank you again!

              • 4. Re: Queation about PRS again!

                Here is an example of a VCO for PSoC3 http://secure.cypress.com/?id=4&rID=58481 the controlling voltage can be produced with a DAC and (now it comes:) the DAC can be fed by DMA at high frequency without CPU usage at all.


                I think you have to try to build a "proof of concept", I would suggest to use a KIT-001 which not only contains a PSoC3 but a PSoC1 and 5 as well (giving you headroom to both sides of enlarging or shrinking your project), a 2-line LCD and a bredboard area. With the included MiniProg3 there are pretty goog debug-capabilities.