More tweaks to wait length calculation

Author: philipstarkey

labscript_devices/PrawnBlaster/blacs_workers.py

@@ -58,7 +58,11 @@ def init(self):
             assert self.prawnblaster.readline().decode() == "ok\r\n"
 
     def check_status(self):
-        if self.started and self.wait_table is not None and self.current_wait < len(self.wait_table):
+        if (
+            self.started
+            and self.wait_table is not None
+            and self.current_wait < len(self.wait_table)
+        ):
             # Try to read out wait. For now, we're only reading out waits from
             # pseudoclock 0 since they should all be the same (requirement imposed by labscript)
             self.prawnblaster.write(b"getwait %d %d\r\n" % (0, self.current_wait))
@@ -67,6 +71,7 @@ def check_status(self):
                 # Parse the response from the PrawnBlaster
                 wait_remaining = int(response)
                 clock_resolution = self.device_properties["clock_resolution"]
+                input_response_time = self.device_properties["input_response_time"]
                 timeout_length = round(
                     self.wait_table[self.current_wait]["timeout"] / clock_resolution
                 )
@@ -80,9 +85,13 @@ def check_status(self):
                     self.wait_timeout[self.current_wait] = True
                 else:
                     # Calculate wait length
+                    # This is a measurement of between the end of the last pulse and the
+                    # retrigger signal. We obtain this by subtracting off the time it takes
+                    # to detect the pulse in the ASM code once the trigger has hit the input
+                    # pin (stored in input_response_time)
                     self.measured_waits[self.current_wait] = (
-                        timeout_length - wait_remaining
-                    ) * clock_resolution
+                        (timeout_length - wait_remaining) * clock_resolution
+                    ) - input_response_time
                     self.wait_timeout[self.current_wait] = False
 
                 self.logger.info(
@@ -142,10 +151,12 @@ def transition_to_buffered(self, device_name, h5file, initial_values, fresh):
         if fresh:
             self.smart_cache = {}
 
+        # fmt: off
         self.h5_file = h5file  # store reference to h5 file for wait monitor
         self.current_wait = 0  # reset wait analysis
         self.started = False   # Prevent status check from detecting previous wait values
-                               # betwen now and when we actually send the start signal
+        #                        betwen now and when we actually send the start signal
+        # fmt: on
 
         # Get data from HDF5 file
         pulse_programs = []

labscript_devices/PrawnBlaster/labscript_devices.py

@@ -107,7 +107,8 @@ class PrawnBlaster(PseudoclockDevice):
     clock_resolution = 10e-9
     # There appears to be ~50ns buffer on input and then we know there is 80ns between
     # trigger detection and first output pulse
-    trigger_delay = 130e-9
+    input_response_time = 50e-9
+    trigger_delay = input_response_time + 80e-9
     # Overestimate that covers indefinite waits (which labscript does not yet support)
     trigger_minimum_duration = 160e-9 
     # There are 4 ASM instructions between end of pulse and being ready to detect
@@ -129,6 +130,7 @@ class PrawnBlaster(PseudoclockDevice):
                 "external_clock_pin",
                 "clock_limit",
                 "clock_resolution",
+                "input_response_time",
                 "trigger_delay",
                 "trigger_minimum_duration",
                 "wait_delay",
@@ -162,6 +164,7 @@ def __init__(
             factor = (1 / clock_frequency) / self.clock_resolution
             self.clock_limit *= factor
             self.clock_resolution *= factor
+            self.input_response_time *= factor
             self.trigger_delay *= factor
             self.trigger_minimum_duration *= factor
             self.wait_delay *= factor