Script that filters VCD files produced by chisel in order to make it load in PulseView (EDIT: This does not seem necessary for the newest git version of sigrok)

fixchiselvcd.py

#! /usr/bin/env python3

import argparse
import pathlib


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("-i", "--input", type=pathlib.Path, required=True)
    parser.add_argument("-o", "--output", type=pathlib.Path, required=True)
    parser.add_argument("-s", "--signal", nargs="+")
    parser.add_argument("-t", "--timescale", type=int)
    args = parser.parse_args()

    with args.input.open() as fin, args.output.open("w") as fout:

        def copy_section(header):
            fout.write(header)
            while not header.endswith("$end\n"):
                header = fin.readline()
                fout.write(header)

        def skip_section(header):
            while not header.endswith("$end\n"):
                header = fin.readline()

        def filter_scope(header):
            fout.write(header)
            var = fin.readline()
            while True:
                var = fin.readline()
                if var.startswith("$upscope"):
                    break
                _, type_, bits, key, name, _ = var.split()
                if bits != "1" or args.signal and name not in args.signal:
                    print("Filtering '{}'".format(name))
                    continue
                fout.write(var)
            fout.write(var)

        def filter_dumpvars(header):
            fout.write(header)
            for line in fin:
                if line[0] == "b" and " " in line:
                    continue
                fout.write(line)

        while True:
            header = fin.readline()
            if not header:
                break
            elif header.startswith("$scope"):
                filter_scope(header)
            elif header.startswith("$dumpvars"):
                filter_dumpvars(header)
            elif header.startswith("$timescale") and args.timescale:
                skip_section(header)
                fout.write("$timescale {}ps  $end\n".format(args.timescale))
            else:
                copy_section(header)