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luaradio/examples/rtlsdr_ax25.lua
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local radio = require('radio') | |
if #arg < 1 then | |
io.stderr:write("Usage: " .. arg[0] .. " <frequency>\n") | |
os.exit(1) | |
end | |
local frequency = tonumber(arg[1]) | |
local tune_offset = -100e3 | |
local baudrate = 1200 | |
-- Blocks | |
local source = radio.RtlSdrSource(frequency + tune_offset, 1000000) | |
local tuner = radio.TunerBlock(tune_offset, 12e3, 80) | |
local nbfm_demod = radio.NBFMDemodulator(3e3, 3e3) | |
local hilbert = radio.HilbertTransformBlock(129) | |
local translator = radio.FrequencyTranslatorBlock(-1700) | |
local afsk_filter = radio.LowpassFilterBlock(128, 750) | |
local afsk_demod = radio.FrequencyDiscriminatorBlock(1.25) | |
local data_filter = radio.LowpassFilterBlock(128, baudrate) | |
local clock_recoverer = radio.ZeroCrossingClockRecoveryBlock(baudrate) | |
local sampler = radio.SamplerBlock() | |
local bit_slicer = radio.SlicerBlock() | |
local bit_decoder = radio.DifferentialDecoderBlock(true) | |
local framer = radio.AX25FramerBlock() | |
local sink = radio.JSONSink() | |
-- Plotting sinks | |
local plot1 = radio.GnuplotSpectrumSink(2048, 'RF Spectrum', {yrange = {-120, -60}}) | |
local plot2 = radio.GnuplotPlotSink(2048, 'Demodulated Bitstream', {yrange = {-0.15, 0.15}}) | |
-- Connections | |
local top = radio.CompositeBlock() | |
top:connect(source, tuner, nbfm_demod) | |
top:connect(nbfm_demod, hilbert, translator, afsk_filter, afsk_demod, data_filter, clock_recoverer) | |
top:connect(data_filter, 'out', sampler, 'data') | |
top:connect(clock_recoverer, 'out', sampler, 'clock') | |
top:connect(sampler, bit_slicer, bit_decoder, framer, sink) | |
if os.getenv('DISPLAY') then | |
top:connect(tuner, plot1) | |
top:connect(data_filter, plot2) | |
end | |
top:run() |