Remove factor 4 in lmsDelay set in setup() if lmsDelay not provided i…

…n pysmurf cfg file. Adjusted cfg file schema to reflect expansion of lmsDelay reg from 5 to 6 bits.

python/pysmurf/client/base/smurf_config.py

@@ -449,12 +449,12 @@ def validate_config(loaded_config):
                 ## TODO remove lmsDelay
                 # lmsDelay is deprected use bandDelayUs instead
 
-                # Matches system latency for LMS feedback (9.6 MHz
-                # ticks, use multiples of 52).  For dspv3 to adjust to
-                # match refPhaseDelay*4 (ignore refPhaseDelayFine for
-                # this).  If not provided and lmsDelay=None, sets to
-                # lmsDelay = 4 x refPhaseDelay.
-                Optional('lmsDelay', default=None) : And(int, lambda n: 0 <= n < 2**5),
+                # Matches system latency for LMS feedback (2.4 MHz
+                # ticks).  For production SMuRF firmware, should set
+                # equal to refPhaseDelay.  (ignore refPhaseDelayFine
+                # for this).  If not provided and lmsDelay=None, sets
+                # to lmsDelay = refPhaseDelay.
+                Optional('lmsDelay', default=None) : And(int, lambda n: 0 <= n < 2**6),
 
                 # Adjust trigRstDly such that the ramp resets at the flux ramp
                 # glitch.  2.4 MHz ticks.

python/pysmurf/client/base/smurf_control.py

@@ -542,13 +542,30 @@ def setup(self, write_log=True, payload_size=2048, force_configure=False, **kwar
                         self._ref_phase_delay_fine[band],
                         write_log=write_log, **kwargs)
 
-                    # in DSPv3, lmsDelay should be 4*refPhaseDelay (says
-                    # Mitch).  If none provided in cfg, enforce that
-                    # constraint.  If provided in cfg, override with provided
-                    # value.
+                    # The lmsDelay register matches the system latency
+                    # for LMS feedback.  The readout has both actuator
+                    # and sensor delay, so this delay is needed to
+                    # compensate the feedback.
+                    #
+                    # actuator being the delay from DSP -> synthesis
+                    # filter bank -> JESD -> DAC -> RF tracked freq
+                    # out
+                    #
+                    # sensor delay being RF in resonator -> ADC input
+                    # -> JESD -> filter bank -> demod (edited)
+                    #
+                    # The delay is needed because we are playing out a
+                    # FM waveform on the RF DACs and it takes ~us to
+                    # get the results.
+                    #
+                    # In production SMuRF firmware, lmsDelay should be
+                    # set equal to refPhaseDelay, and both are
+                    # integers that count 2.4 MHz ticks.  If none
+                    # provided in cfg, enforce that constraint.  If
+                    # provided in cfg, override with provided value.
                     if self._lms_delay[band] is None:
                         self.set_lms_delay(
-                            band, int(4*self._ref_phase_delay[band]),
+                            band, int(self._ref_phase_delay[band]),
                             write_log=write_log, **kwargs)
                     else:
                         self.set_lms_delay(