suservo: coeff mem write port READ_FIRST

artiq/coredevice/suservo.py

@@ -95,10 +95,12 @@ class SUServo:
     def set_config(self, enable):
         """Set SU Servo configuration.
 
+        Disabling takes up to 2 Servo cycles (~2.2 µs) to clear
+        the processing pipeline.
+
         This method advances the timeline by one Servo memory access.
 
-        :param enable: Enable Servo operation. Disabling takes up to 2 Servo
-            cycles (~2.2 µs).
+        :param enable: Enable Servo operation.
         """
         self.write(CONFIG_ADDR, enable)
 
@@ -261,6 +263,10 @@ class Channel:
         The IIR state is also know as the "integrator", or the DDS amplitude
         scale factor. It is 18 bits wide and unsigned.
 
+        This method must not be used when the Servo
+        could be writing to the same location. Either deactivate the profile,
+        or deactivate IIR updates, or disable Servo iterations.
+
         This method advances the timeline by one Servo memory access.
 
         :param profile: Profile number (0-31)

artiq/examples/kasli_suservo/repository/suservo.py

@@ -30,11 +30,13 @@ class SUServo(EnvExperiment):
         self.suservo0.cpld0.set_att_mu(0, 64)
         delay(1*us)
         assert self.suservo0.get_status() == 2
+        delay(10*us)
 
         # set up profile 0 on channel 0
         self.suservo0_ch0.set_y_mu(0, 0)
         self.suservo0_ch0.set_iir_mu(
                 profile=0, adc=0, a1=-0x800, b0=0x1000, b1=0, delay=0)
+        delay(10*us)
         self.suservo0_ch0.set_dds_mu(
                 profile=0, ftw=0x12345667, offset=0x1, pow=0xaa55)
         # enable channel
@@ -50,6 +52,7 @@ class SUServo(EnvExperiment):
 
         # check servo status
         assert self.suservo0.get_status() == 1
+        delay(10*us)
 
         # reach back ADC data
         print(self.suservo0.get_adc_mu(0))

artiq/gateware/rtio/phy/servo.py

@@ -28,9 +28,11 @@ class RTServoMem(Module):
     interface."""
     def __init__(self, w, servo):
         m_coeff = servo.iir.m_coeff.get_port(write_capable=True,
+                mode=READ_FIRST,
                 we_granularity=w.coeff, clock_domain="rio")
         assert len(m_coeff.we) == 2
         m_state = servo.iir.m_state.get_port(write_capable=True,
+                # mode=READ_FIRST,
                 clock_domain="rio")
         self.specials += m_state, m_coeff
 

artiq/gateware/suservo/iir.py

@@ -344,7 +344,7 @@ class IIR(Module):
         ]
 
         m_coeff = self.m_coeff.get_port()
-        m_state = self.m_state.get_port(write_capable=True)
+        m_state = self.m_state.get_port(write_capable=True)  # mode=READ_FIRST
         self.specials += m_state, m_coeff
 
         dsp = DSP(w)