Pending the inclusion of more sophisticated filter design software with Ptolemy, this distribution includes two Fortran programs for this purpose. These design FIR filters using the Parks-McClellan algorithm or the window method. The frequency sampling method can be done directly using Ptolemy stars, as shown in the demos included with the SDF domain.
These programs can be invoked standalone or through the filter command in pigi. If invoked through
pigi, then an
xterm window will be opened and the program started.
Filter specifications can be entered by hand or loaded from a file. The first prompt from the program is the name of the input command file. Simply typing return will result in manual entry. To enter data from a file, the data should appear in the file in exactly the order that it would appear if it were being entered by hand, with one question answered per line. Unfortunately, these command files are rather difficult to read, and not too easy to create correctly. It is recommended to first do manual entry, then imitate the entries in a file. Data can be entered in any reasonable numeric format.
These are public domain Fortran programs that have been converted from C, provided for convenience; they are not an integral part of Ptolemy. Incorrect formatting of data line can lead to ungraceful exits (often with a core dump) or incorrect results. Either program can be invoked through the Ptolemy graphical interface, in which case it is started in its own window, in the background. Note that in this case the program always starts in the current working directory of
pigi, probably your home directory.
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