add am demodulator chain

csdr/__init__.py

@@ -37,6 +37,7 @@ from csdr.pipe import Pipe
 
 from csdr.chain.demodulator import DemodulatorChain
 from csdr.chain.fm import Fm
+from csdr.chain.am import Am
 
 import logging
 
@@ -118,9 +119,13 @@ class Dsp(DirewolfConfigSubscriber):
         self.pipe_base_path = "{tmp_dir}/openwebrx_pipe_".format(tmp_dir=self.temporary_directory)
 
     def chain(self, which):
-        if self.pycsdr_enabled and which == "nfm":
+        if self.pycsdr_enabled:
+            if which == "nfm":
                 self.pycsdr_chain = DemodulatorChain(self.samp_rate, self.get_audio_rate(), 0.0, Fm(self.get_audio_rate()))
                 return self.pycsdr_chain
+            elif which == "am":
+                self.pycsdr_chain = DemodulatorChain(self.samp_rate, self.get_audio_rate(), 0.0, Am())
+                return self.pycsdr_chain
 
         chain = ["nc -v 127.0.0.1 {nc_port}"]
         chain += ["csdr shift_addfast_cc --fifo {shift_pipe}"]

csdr/chain/am.py

@@ -0,0 +1,23 @@
+from csdr.chain import Chain
+from csdr.chain.demodulator import Demodulator
+from pycsdr.modules import AmDemod, DcBlock, Agc, Convert
+from pycsdr.types import Format
+
+
+class Am(Demodulator):
+    def __init__(self):
+        workers = [
+            AmDemod(),
+            DcBlock(),
+            # empty chain as placeholder for the "last decimation"
+            Chain(),
+            Agc(Format.FLOAT),
+            Convert(Format.FLOAT, Format.SHORT),
+        ]
+
+        super().__init__(*workers)
+
+    def setLastDecimation(self, decimation: Chain):
+        # TODO: build api to replace workers
+        # TODO: replace placeholder
+        pass