4410: modify ram example

* Use `prepare()` to init the arrays, would be great if the value can be prepared there. However, the type check was not happy about it.
* Separate RAM configuration into a separate function
* Separate DDS init, digital attenuation & switch config in an init function
* Use `dds.set()`. It is supposed to look simple.

All these are to avoid repeating the long code in the coming RAM+SYNC example.

4410-4412.tex

@@ -457,39 +457,49 @@ It can be negated by adjusting the \texttt{phase} parameter.
 \newpage
 \subsection{DDS RAM Modulation (AD9910 Only)}
 This examples demonstrates that the RF signal can be modulated by amplitude using the RAM modulation feature of AD9910.
-Set field \texttt{dds} as an Urukul channel, \texttt{cpld} as the corresponding Urukul CPLD.
+By default, RAM profiles are programmed to profile 0.
 
 \begin{minted}{python}
 from artiq.coredevice.ad9910 import RAM_MODE_CONT_RAMPUP
 
+def prepare(self):
+    self.amp = [0.0, 0.0, 0.0, 0.7, 0.0, 0.7, 0.7] # Reversed Order
+    self.asf_ram = [0] * len(self.amp)
+
+@kernel
+def init_dds(self, dds):
+    self.core.break_realtime()
+    dds.init()
+    dds.set_att(6.)
+    dds.cfg_sw(True)
+
+@kernel
+def configure_ram_mode(self, dds):
+    self.core.break_realtime()
+    dds.set_cfr1(ram_enable=0)
+    self.cpld.io_update.pulse_mu(8)
+    self.cpld.set_profile(0)    # Enable the corresponding RAM profile
+                                # Profile 0 is the default
+    dds.set_profile_ram(start=0, end=len(self.asf_ram)-1,
+        step=250, profile=0, mode=RAM_MODE_CONT_RAMPUP)
+    self.cpld.io_update.pulse_mu(8)
+    dds.amplitude_to_ram(self.amp, self.asf_ram)
+    dds.write_ram(self.asf_ram)
+
+    dds.set(10*MHz, profile=-1)
+    # Pass osk_enable=1 to set_cfr1() if it is not an amplitude RAM
+    dds.set_cfr1(ram_enable=1, ram_destination=RAM_DEST_ASF)
+
+    self.cpld.io_update.pulse_mu(8)
+    
 @kernel
 def run(self):
     self.core.reset()
     self.core.break_realtime()
     self.cpld.init()
-    self.dds.init()
 
-    self.core.break_realtime()
-    self.profile0_set()
-    self.dds.set_att(6.)
-    self.dds.sw.on()
-
-    self.cpld.set_profile(0)
-    
-@kernel
-def profile0_set(self):
-    self.dds.set_cfr1(ram_enable = 0)
-    self.cpld.set_profile(0)
-    amp_ram = [0.0, 0.0, 0.0, 0.7, 0.0, 0.7, 0.7] # Reversed Order
-    asf_ram = [0] * len(amp_ram)
-    self.dds.set_profile_ram(start=0, end=len(amp_ram)-1,
-        step=250, profile=0, mode=RAM_MODE_CONT_RAMPUP)
-    self.cpld.io_update.pulse_mu(8)
-    self.dds.amplitude_to_ram(amp_ram, asf_ram)
-    self.dds.write_ram(asf_ram)
-    self.dds.set_cfr1(ram_enable=1, ram_destination=RAM_DEST_ASF)
-    self.dds.set_frequency(10*MHz)
-    self.cpld.io_update.pulse_mu(8)
+    self.init_dds(self.dds0)
+    self.configure_ram_mode(self.dds0)
 \end{minted}
 
 The generated RF output of the above example consists of the following features in sequence: