composites/bpsk31receiver: add BPSK31Receiver

radio/composites/bpsk31receiver.lua

@@ -0,0 +1,49 @@
+---
+-- Demodulate and decode bytes from a baseband BPSK31 modulated complex-valued
+-- signal.
+--
+-- @category Receivers
+-- @block BPSK31Receiver
+--
+-- @signature in:ComplexFloat32 > out:Byte
+--
+-- @usage
+-- local receiver = radio.BPSK31Receiver()
+-- local snk = radio.RawFileSink(io.stdout)
+-- top:connect(src, receiver, snk)
+
+local block = require('radio.core.block')
+local types = require('radio.types')
+local blocks = require('radio.blocks')
+
+local BPSK31Receiver = block.factory("BPSK31Receiver", blocks.CompositeBlock)
+
+function BPSK31Receiver:instantiate()
+    blocks.CompositeBlock.instantiate(self)
+
+    local bandwidth = 100
+    local baudrate = 31.25
+
+    local filter = blocks.LowpassFilterBlock(128, bandwidth)
+    local rrc_filter = blocks.RootRaisedCosineFilterBlock(101, 1, baudrate)
+    local phase_corrector = blocks.BinaryPhaseCorrectorBlock(50)
+    local clock_demod = blocks.ComplexToRealBlock()
+    local clock_recoverer = blocks.ZeroCrossingClockRecoveryBlock(baudrate)
+    local sampler = blocks.SamplerBlock()
+    local bit_demod = blocks.ComplexToRealBlock()
+    local slicer = blocks.SlicerBlock()
+    local bit_decoder = blocks.DifferentialDecoderBlock(true)
+    local decoder = blocks.VaricodeDecoderBlock()
+
+    self:connect(filter, rrc_filter, phase_corrector)
+    self:connect(phase_corrector, clock_demod, clock_recoverer)
+    self:connect(phase_corrector, 'out', sampler, 'data')
+    self:connect(clock_recoverer, 'out', sampler, 'clock')
+    self:connect(sampler, bit_demod, slicer, bit_decoder, decoder)
+
+    self:add_type_signature({block.Input("in", types.ComplexFloat32)}, {block.Output("out", types.Byte)})
+    self:connect(self, "in", filter, "in")
+    self:connect(self, "out", decoder, "out")
+end
+
+return BPSK31Receiver

radio/composites/init.lua

@@ -22,4 +22,5 @@ return {
     RDSReceiver = require('radio.composites.rdsreceiver'),
     AX25Receiver = require('radio.composites.ax25receiver'),
     POCSAGReceiver = require('radio.composites.pocsagreceiver'),
+    BPSK31Receiver = require('radio.composites.bpsk31receiver'),
 }