pico-tracker/sim/si_fir_filter/README.md

Design of the Si TX Spectral Shaping Filter

The SI contains a 17-tap digital FIR filter for use in GFSK modes.

We use this in aprs mode to filter the gpio squarewave into a sensible afsk signal.

There's some notes in a ipython notebook si_fir_filter.ipynp on this. This notebook is also used to calculate the deviation values.

Prerequisites

sudo apt-get install ipython libblas-dev liblapack-dev gfortran
pip install scipy matplotlib

Yes you need a fortran compiler!!!

Python Usage

ipython notebook

Calcuating new coefficients

There's an awesome calculator here here

So

The python script is from here