![]() Logic StructureĪ high level block diagram that describes the logical structure of the project is shown below.Įssentially, the logical flow of the program is as follows. The creators of this project also believed that this would be a fun and challenging project, and decided to undertake it. The source for this project idea was Bruce Land, who thought that it would be a good idea to make a project that allowed users to specify arbitrary filter transfer functions that could be used for digital signal processing. Full System, showing PIC32, touchscreen, and interfaces at start up Pictured blow is a figure of the entire system, with input from a signal generator and output to an oscilloscope off-screen.įigure 1. In this way, a user can design their filter and see it implemented in real time. With discrete time finite impulse response (FIR) filter coefficients a real time convolution is taken with an analog to digital converter sampled input signal and then output to a 12-bit digital to analog converter. These bands are used as the argument to either a Parks- McClellan or Fourier Transform algorithm which creates the discrete time impulse response coefficients corresponding to the drawn frequency response. For a video of our lab demo please see Project DemoĪ user is given the ability to draw a transfer function on a touchscreen interfaced with the PIC, a custom interpolation and interpretation algorithm is used to understand the essential pass and stop bands of the users transfer function. The project gets its premise out of the frequent requirement for arbitrary digital signal filters in a laboratory setting. This laboratory aims to implement a custom filter designer on the PIC32 microcontroller for the purpose of real time signal transformation. “DESIGN OF NONRECURSIVE (FIR FILTERS)” at /SupMaterials/Slides/DSP-Ch09-S3,4.pdf."A real time signal transformation based on a user constructed FIR filter" Chamira Edussooriya in 2016 at the Department of Electronic and Telecommunication Engineering, University of Moratuwa References You can find the complete code for the filter design at Īcknowledgment: This content was originally submitted as partial fulfillment for the module EN2570: Digital Signal Processing taught by Dr. Stopband ripples distort the signals that need attenuation.Non-zero magnitude response in the stopband for the designed filter.Passband ripples cause undesirable modifications to the required part of the spectrum.There is a slight difference between ideally expected output and the obtained one due to the following reasons. It is evident from the results shown in figure 5 that the filter blocks the undesired signals and passed the signals within the passband. The filter designed for the purpose of this assignment truly acts as a bandpass filter of the stipulated parameters. Image 3 shows the actual filtered output which closely resembles the expected output. The second image shows the frequency spectrum of the expected output where only the signal within the passband gets passed to the output. In figure 5 the first image shows the frequency spectrum of the input signal which is a combination of 3 sinusoids. Figure 3 shows the ripples in the passband even though they are invisible in figure 1. In figure 1 it can be seen that the frequency spectrum of the filter resembles a bandpass filter.
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