drtio: add pulse rate example

artiq/examples/drtio/repository/pulse_rate.py

@@ -0,0 +1,26 @@
+from artiq.experiment import *
+
+
+class PulseRate(EnvExperiment):
+    def build(self):
+        self.setattr_device("core")
+        self.setattr_device("rsmap")
+
+    @kernel
+    def run(self):
+        #self.core.reset()
+        self.core.break_realtime()
+
+        dt = seconds_to_mu(300*ns)
+        while True:
+            for i in range(10000):
+                try:
+                    self.rsmap.pulse_mu(dt)
+                    delay_mu(dt)
+                except RTIOUnderflow:
+                    dt += 1
+                    self.core.break_realtime()
+                    break
+            else:
+                print(mu_to_seconds(dt))
+                return