iqfile_converter.zig

This example is an IQ file format converter. It converts the binary encoding of IQ files from one format, e.g. signed 8-bit, to another, e.g. 32-bit float little endian. This example doesn't use an SDR source at all, but instead demonstrates how you can build file-based command-line utilities with modulation, demodulation, decoding, file conversion, etc. flow graphs that run to completion.

Source

const std = @import("std");

const radio = @import("radio");

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};

    const args = try std.process.argsAlloc(gpa.allocator());
    defer std.process.argsFree(gpa.allocator(), args);

    if (args.len < 2) {
        std.debug.print("Usage: {s} <frequency>\n", .{args[0]});
        std.posix.exit(1);
    }

    const frequency = try std.fmt.parseFloat(f64, args[1]);
    const tune_offset = -50e3;
    const bandwidth = 5e3;

    var source = radio.blocks.RtlSdrSource.init(frequency + tune_offset, 960000, .{ .debug = true });
    var tuner = radio.blocks.TunerBlock.init(tune_offset, 2 * bandwidth, 10);
    var pll = radio.blocks.ComplexPLLBlock.init(500, .{ -100, 100 }, .{});
    var mixer = radio.blocks.MultiplyConjugateBlock.init();
    var am_demod = radio.blocks.ComplexToRealBlock.init();
    var dcr_filter = radio.blocks.SinglepoleHighpassFilterBlock(f32).init(100);
    var af_filter = radio.blocks.LowpassFilterBlock(f32, 128).init(bandwidth, .{});
    var af_gain = radio.blocks.AGCBlock(f32).init(.{ .preset = .Slow }, .{});
    var af_downsampler = radio.blocks.DownsamplerBlock(f32).init(2);
    var sink = radio.blocks.PulseAudioSink(1).init();

    var top = radio.Flowgraph.init(gpa.allocator(), .{ .debug = true });
    defer top.deinit();
    try top.connect(&source.block, &tuner.block);
    try top.connect(&tuner.block, &pll.block);
    try top.connectPort(&tuner.block, "out1", &mixer.block, "in1");
    try top.connectPort(&pll.block, "out1", &mixer.block, "in2");
    try top.connect(&mixer.block, &am_demod.block);
    try top.connect(&am_demod.block, &dcr_filter.block);
    try top.connect(&dcr_filter.block, &af_filter.block);
    try top.connect(&af_filter.block, &af_gain.block);
    try top.connect(&af_gain.block, &af_downsampler.block);
    try top.connect(&af_downsampler.block, &sink.block);

    try top.start();
    radio.platform.waitForInterrupt();
    _ = try top.stop();
}

Usage

Usage: ./zig-out/bin/example-iqfile_converter <input IQ file> <input format> <output IQ file> <output format>
Supported formats: u8, s8, u16le, u16be, s16le, s16be, u32le, u32be, s32le, s32be, f32le, f32be, f64le, f64be

For example, convert test.u8.iq, with unsigned 8-bit samples, to test.f32le.iq, with 32-bit float little endian samples:

$ ./zig-out/bin/example-iqfile_converter test.u8.iq u8 test.f32le.iq f32le