Automatic Signal Transformer and Custom Filter Designer

Manish Patel ( mkp53@cornell.edu )

"A real time signal transformation based on a user constructed FIR filter"

This laboratory aims to implement a custom filter designer on the PIC32 microcontroller for the purpose of real time signal transformation. The project gets its premise out of the frequent requirement for arbitrary digital signal filters in a laboratory setting. For a video of our lab demo please see Project Demo

A 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. 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. 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. In this way, a user can design their filter and see it implemented in real time. Pictured blow is a figure of the entire system, with input from a signal generator and output to an oscilloscope off-screen.

Figure 1. Full System, showing PIC32, touchscreen, and interfaces at start up

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