gr-digital: replace clk recovery MM in hier blks

As Clock Recovery MM is deprecated, this commit replaces them
in the hier blocks, gmfsk demod and gfsk demod, with Andy Wall's Symbol
Sync block. Backward compatibility is maintained by keeping the
parameters unchanged, and converting the two gain values to the
corresponding loop bandwidth value that Symbol Sync requires.

Even though `mu` parameter's services is no longer required, we leave it
in the hier block for backward compatibility purposes.

Signed-off-by: Solomon Tan <solomonbstoner@yahoo.com.au>

4 files changed, 52 insertions, 28 deletions

diff --git a/gr-digital/grc/digital_gfsk_demod.block.yml b/gr-digital/grc/digital_gfsk_demod.block.yml
index 042af89a2..cbe75b9f7 100644
--- a/gr-digital/grc/digital_gfsk_demod.block.yml
+++ b/gr-digital/grc/digital_gfsk_demod.block.yml
@@ -16,7 +16,7 @@ parameters:
     dtype: real
     default: '0.175'
 -   id: mu
-    label: Mu
+    label: Mu (Unused)
     dtype: real
     default: '0.5'
 -   id: omega_relative_limit
diff --git a/gr-digital/grc/digital_gmsk_demod.block.yml b/gr-digital/grc/digital_gmsk_demod.block.yml
index b47859371..2ec9f5896 100644
--- a/gr-digital/grc/digital_gmsk_demod.block.yml
+++ b/gr-digital/grc/digital_gmsk_demod.block.yml
@@ -12,7 +12,7 @@ parameters:
     dtype: real
     default: '0.175'
 -   id: mu
-    label: Mu
+    label: Mu (Unused)
     dtype: real
     default: '0.5'
 -   id: omega_relative_limit
diff --git a/gr-digital/python/digital/gfsk.py b/gr-digital/python/digital/gfsk.py
index befc55071..4f47aebea 100644
--- a/gr-digital/python/digital/gfsk.py
+++ b/gr-digital/python/digital/gfsk.py
@@ -12,6 +12,7 @@
 
 
 # See gnuradio-examples/python/digital for examples
+from math import log as ln
 
 import numpy
 
@@ -190,7 +191,7 @@ class gfsk_demod(gr.hier_block2):
 
         Args:
             gain_mu: controls rate of mu adjustment (float)
-            mu: fractional delay [0.0, 1.0] (float)
+            mu: unused but unremoved for backward compatibility (unused)
             omega_relative_limit: sets max variation in omega (float, typically 0.000200 (200 ppm))
             freq_error: bit rate error as a fraction
             float:
@@ -202,7 +203,6 @@ class gfsk_demod(gr.hier_block2):
 
         self._samples_per_symbol = samples_per_symbol
         self._gain_mu = gain_mu
-        self._mu = mu
         self._omega_relative_limit = omega_relative_limit
         self._freq_error = freq_error
         self._differential = False
@@ -217,15 +217,27 @@ class gfsk_demod(gr.hier_block2):
 
         self._gain_omega = .25 * self._gain_mu * self._gain_mu        # critically damped
 
+        self._damping = 1.0
+        self._loop_bw = -ln((self._gain_mu + self._gain_omega)/(-2.0) + 1)        # critically damped
+        self._max_dev = self._omega_relative_limit * self._samples_per_symbol
+
         # Demodulate FM
         #sensitivity = (pi / 2) / samples_per_symbol
         self.fmdemod = analog.quadrature_demod_cf(1.0 / sensitivity)
 
         # the clock recovery block tracks the symbol clock and resamples as needed.
         # the output of the block is a stream of soft symbols (float)
-        self.clock_recovery = digital.clock_recovery_mm_ff(self._omega, self._gain_omega,
-                                                           self._mu, self._gain_mu,
-                                                           self._omega_relative_limit)
+        self.clock_recovery = self.digital_symbol_sync_xx_0 = digital.symbol_sync_ff(digital.TED_MUELLER_AND_MULLER,
+                            self._omega,
+                            self._loop_bw,
+                            self._damping,
+                            1.0,  # Expected TED gain
+                            self._max_dev,
+                            1,  # Output sps
+                            digital.constellation_bpsk().base(),
+                            digital.IR_MMSE_8TAP,
+                            128,
+                            [])
 
         # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample
         self.slicer = digital.binary_slicer_fb()
@@ -248,10 +260,10 @@ class gfsk_demod(gr.hier_block2):
 
     def _print_verbage(self):
         print("bits per symbol = %d" % self.bits_per_symbol())
-        print("M&M clock recovery omega = %f" % self._omega)
-        print("M&M clock recovery gain mu = %f" % self._gain_mu)
-        print("M&M clock recovery mu = %f" % self._mu)
-        print("M&M clock recovery omega rel. limit = %f" % self._omega_relative_limit)
+        print("Symbol Sync M&M omega = %f" % self._omega)
+        print("Symbol Sync M&M gain mu = %f" % self._gain_mu)
+        print("M&M clock recovery mu (Unused) = %f" % self._mu)
+        print("Symbol Sync M&M omega rel. limit = %f" % self._omega_relative_limit)
         print("frequency error = %f" % self._freq_error)
 
 
@@ -270,13 +282,13 @@ class gfsk_demod(gr.hier_block2):
         Adds GFSK demodulation-specific options to the standard parser
         """
         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
-                          help="M&M clock recovery gain mu [default=%default] (GFSK/PSK)")
+                          help="Symbol Sync M&M gain mu [default=%default] (GFSK/PSK)")
         parser.add_option("", "--mu", type="float", default=_def_mu,
-                          help="M&M clock recovery mu [default=%default] (GFSK/PSK)")
+                          help="M&M clock recovery mu [default=%default] (Unused)")
         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
-                          help="M&M clock recovery omega relative limit [default=%default] (GFSK/PSK)")
+                          help="Symbol Sync M&M omega relative limit [default=%default] (GFSK/PSK)")
         parser.add_option("", "--freq-error", type="float", default=_def_freq_error,
-                          help="M&M clock recovery frequency error [default=%default] (GFSK)")
+                          help="Symbol Sync M&M frequency error [default=%default] (GFSK)")
 
     @staticmethod
     def extract_kwargs_from_options(options):
diff --git a/gr-digital/python/digital/gmsk.py b/gr-digital/python/digital/gmsk.py
index cf998391c..68127119e 100644
--- a/gr-digital/python/digital/gmsk.py
+++ b/gr-digital/python/digital/gmsk.py
@@ -14,6 +14,7 @@
 # See gnuradio-examples/python/digital for examples
 
 from math import pi
+from math import log as ln
 from pprint import pprint
 import inspect
 
@@ -167,7 +168,7 @@ class gmsk_demod(gr.hier_block2):
     Args:
         samples_per_symbol: samples per baud (integer)
         gain_mu: controls rate of mu adjustment (float)
-        mu: fractional delay [0.0, 1.0] (float)
+        mu: unused but unremoved for backward compatibility (unused)
         omega_relative_limit: sets max variation in omega (float)
         freq_error: bit rate error as a fraction (float)
         verbose: Print information about modulator? (boolean)
@@ -189,7 +190,6 @@ class gmsk_demod(gr.hier_block2):
 
         self._samples_per_symbol = samples_per_symbol
         self._gain_mu = gain_mu
-        self._mu = mu
         self._omega_relative_limit = omega_relative_limit
         self._freq_error = freq_error
         self._differential = False
@@ -204,15 +204,27 @@ class gmsk_demod(gr.hier_block2):
 
         self._gain_omega = .25 * self._gain_mu * self._gain_mu        # critically damped
 
+        self._damping = 1.0
+        self._loop_bw = -ln((self._gain_mu + self._gain_omega)/(-2.0) + 1)        # critically damped
+        self._max_dev = self._omega_relative_limit * self._samples_per_symbol
+
         # Demodulate FM
         sensitivity = (pi / 2) / samples_per_symbol
         self.fmdemod = analog.quadrature_demod_cf(1.0 / sensitivity)
 
         # the clock recovery block tracks the symbol clock and resamples as needed.
         # the output of the block is a stream of soft symbols (float)
-        self.clock_recovery = digital.clock_recovery_mm_ff(self._omega, self._gain_omega,
-                                                           self._mu, self._gain_mu,
-                                                           self._omega_relative_limit)
+        self.clock_recovery = self.digital_symbol_sync_xx_0 = digital.symbol_sync_ff(digital.TED_MUELLER_AND_MULLER,
+                            self._omega,
+                            self._loop_bw,
+                            self._damping,
+                            1.0,  # Expected TED gain
+                            self._max_dev,
+                            1,  # Output sps
+                            digital.constellation_bpsk().base(),
+                            digital.IR_MMSE_8TAP,
+                            128,
+                            [])
 
         # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample
         self.slicer = digital.binary_slicer_fb()
@@ -235,10 +247,10 @@ class gmsk_demod(gr.hier_block2):
 
     def _print_verbage(self):
         print("bits per symbol = %d" % self.bits_per_symbol())
-        print("M&M clock recovery omega = %f" % self._omega)
-        print("M&M clock recovery gain mu = %f" % self._gain_mu)
-        print("M&M clock recovery mu = %f" % self._mu)
-        print("M&M clock recovery omega rel. limit = %f" % self._omega_relative_limit)
+        print("Symbol Sync M&M omega = %f" % self._omega)
+        print("Symbol Sync M&M gain mu = %f" % self._gain_mu)
+        print("M&M clock recovery mu (Unused) = %f" % self._mu)
+        print("Symbol Sync M&M omega rel. limit = %f" % self._omega_relative_limit)
         print("frequency error = %f" % self._freq_error)
 
 
@@ -257,13 +269,13 @@ class gmsk_demod(gr.hier_block2):
         Adds GMSK demodulation-specific options to the standard parser
         """
         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
-                          help="M&M clock recovery gain mu [default=%default] (GMSK/PSK)")
+                          help="Symbol Sync M&M gain mu [default=%default] (GMSK/PSK)")
         parser.add_option("", "--mu", type="float", default=_def_mu,
-                          help="M&M clock recovery mu [default=%default] (GMSK/PSK)")
+                          help="M&M clock recovery mu [default=%default] (Unused)")
         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
-                          help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
+                          help="Symbol Sync M&M omega relative limit [default=%default] (GMSK/PSK)")
         parser.add_option("", "--freq-error", type="float", default=_def_freq_error,
-                          help="M&M clock recovery frequency error [default=%default] (GMSK)")
+                          help="Symbol Sync M&M frequency error [default=%default] (GMSK)")
 
     @staticmethod
     def extract_kwargs_from_options(options):