experiment/gui: support reverse scan (closes #246)

RELEASE_NOTES.rst

@@ -10,9 +10,13 @@ Release notes
 * Core device flash storage has moved due to increased runtime size.
   This requires reflashing the runtime and the flash storage filesystem image
   or erase and rewrite its entries.
-* RTIOCollisionError has been renamed to RTIOCollision
+* ``RTIOCollisionError`` has been renamed to ``RTIOCollision``
-* the new API for DDS batches is:
+* the new API for DDS batches is::
     with self.core_dds.batch:
        ...
-  with core_dds a device of type artiq.coredevice.dds.CoreDDS.
+
+  with ``core_dds`` a device of type ``artiq.coredevice.dds.CoreDDS``.
   The dds_bus device should not be used anymore.
+* LinearScan now supports scanning from high to low. Accordingly,
+  it's arguments ``min/max`` have been renamed to ``start/stop`` respectively.
+  Same for RandomScan (even though there direction matters little).

artiq/gui/entries.py

@@ -154,52 +154,52 @@ class _RangeScan(LayoutWidget):
             if procdesc["unit"]:
                 spinbox.setSuffix(" " + procdesc["unit"])
 
-        self.scanner = scanner = ScanWidget()
+        scanner = ScanWidget()
         disable_scroll_wheel(scanner)
         self.addWidget(scanner, 0, 0, -1, 1)
 
-        self.min = ScientificSpinBox()
+        start = ScientificSpinBox()
-        self.min.setStyleSheet("QDoubleSpinBox {color:blue}")
+        start.setStyleSheet("QDoubleSpinBox {color:blue}")
-        self.min.setMinimumSize(110, 0)
+        start.setMinimumSize(110, 0)
-        self.min.setSizePolicy(QtWidgets.QSizePolicy(
+        start.setSizePolicy(QtWidgets.QSizePolicy(
             QtWidgets.QSizePolicy.Fixed, QtWidgets.QSizePolicy.Fixed))
-        disable_scroll_wheel(self.min)
+        disable_scroll_wheel(start)
-        self.addWidget(self.min, 0, 1)
+        self.addWidget(start, 0, 1)
 
-        self.npoints = QtWidgets.QSpinBox()
+        npoints = QtWidgets.QSpinBox()
-        self.npoints.setMinimum(1)
+        npoints.setMinimum(1)
-        disable_scroll_wheel(self.npoints)
+        disable_scroll_wheel(npoints)
-        self.addWidget(self.npoints, 1, 1)
+        self.addWidget(npoints, 1, 1)
 
-        self.max = ScientificSpinBox()
+        stop = ScientificSpinBox()
-        self.max.setStyleSheet("QDoubleSpinBox {color:red}")
+        stop.setStyleSheet("QDoubleSpinBox {color:red}")
-        self.max.setMinimumSize(110, 0)
+        stop.setMinimumSize(110, 0)
-        disable_scroll_wheel(self.max)
+        disable_scroll_wheel(stop)
-        self.addWidget(self.max, 2, 1)
+        self.addWidget(stop, 2, 1)
 
-        def update_min(value):
+        def update_start(value):
-            state["min"] = value*scale
+            state["start"] = value*scale
             scanner.setStart(value)
 
-        def update_max(value):
+        def update_stop(value):
-            state["max"] = value*scale
+            state["stop"] = value*scale
             scanner.setStop(value)
 
         def update_npoints(value):
             state["npoints"] = value
             scanner.setNum(value)
 
-        scanner.startChanged.connect(self.min.setValue)
+        scanner.startChanged.connect(start.setValue)
-        scanner.numChanged.connect(self.npoints.setValue)
+        scanner.numChanged.connect(npoints.setValue)
-        scanner.stopChanged.connect(self.max.setValue)
+        scanner.stopChanged.connect(stop.setValue)
-        self.min.valueChanged.connect(update_min)
+        start.valueChanged.connect(update_start)
-        self.npoints.valueChanged.connect(update_npoints)
+        npoints.valueChanged.connect(update_npoints)
-        self.max.valueChanged.connect(update_max)
+        stop.valueChanged.connect(update_stop)
-        scanner.setStart(state["min"]/scale)
+        scanner.setStart(state["start"]/scale)
         scanner.setNum(state["npoints"])
-        scanner.setStop(state["max"]/scale)
+        scanner.setStop(state["stop"]/scale)
-        apply_properties(self.min)
+        apply_properties(start)
-        apply_properties(self.max)
+        apply_properties(stop)
 
 
 class _ExplicitScan(LayoutWidget):
@@ -266,8 +266,8 @@ class _ScanEntry(LayoutWidget):
         state = {
             "selected": "NoScan",
             "NoScan": {"value": 0.0},
-            "LinearScan": {"min": 0.0, "max": 100.0*scale, "npoints": 10},
+            "LinearScan": {"start": 0.0, "stop": 100.0*scale, "npoints": 10},
-            "RandomScan": {"min": 0.0, "max": 100.0*scale, "npoints": 10},
+            "RandomScan": {"start": 0.0, "stop": 100.0*scale, "npoints": 10},
             "ExplicitScan": {"sequence": []}
         }
         if "default" in procdesc:
@@ -278,8 +278,8 @@ class _ScanEntry(LayoutWidget):
                 state["NoScan"]["value"] = default["value"]
             elif ty == "LinearScan" or ty == "RandomScan":
                 for d in state["LinearScan"], state["RandomScan"]:
-                    d["min"] = default["min"]
+                    d["start"] = default["start"]
-                    d["max"] = default["max"]
+                    d["stop"] = default["stop"]
                     d["npoints"] = default["npoints"]
             elif ty == "ExplicitScan":
                 state["ExplicitScan"]["sequence"] = default["sequence"]

artiq/language/scan.py

@@ -11,7 +11,7 @@ Iterate on a scan object to scan it, e.g. ::
         do_something(variable)
 
 Iterating multiple times on the same scan object is possible, with the scan
-restarting at the minimum value each time. Iterating concurrently on the
+yielding the same values each time. Iterating concurrently on the
 same scan object (e.g. via nested loops) is also supported, and the
 iterators are independent from each other.
 
@@ -55,21 +55,23 @@ class NoScan(ScanObject):
 
 
 class LinearScan(ScanObject):
-    """A scan object that yields a fixed number of increasing evenly
+    """A scan object that yields a fixed number of evenly
     spaced values in a range."""
-    def __init__(self, min, max, npoints):
+    def __init__(self, start, stop, npoints):
-        if min > max:
+        self.start = start
-            raise ValueError("Scan minimum must be less than maximum")
+        self.stop = stop
-        self.min = min
-        self.max = max
         self.npoints = npoints
 
     @portable
     def _gen(self):
-        r = self.max - self.min
+        if self.npoints == 0:
-        d = self.npoints - 1
+            return
-        for i in range(self.npoints):
+        if self.npoints == 1:
-            yield r*i/d + self.min
+            yield self.start
+        else:
+            dx = (self.stop - self.start)/(self.npoints - 1)
+            for i in range(self.npoints):
+                yield i*dx + self.start
 
     @portable
     def __iter__(self):
@@ -80,19 +82,18 @@ class LinearScan(ScanObject):
 
     def describe(self):
         return {"ty": "LinearScan",
-                "min": self.min, "max": self.max, "npoints": self.npoints}
+                "start": self.start, "stop": self.stop,
+                "npoints": self.npoints}
 
 
 class RandomScan(ScanObject):
     """A scan object that yields a fixed number of randomly ordered evenly
     spaced values in a range."""
-    def __init__(self, min, max, npoints, seed=0):
+    def __init__(self, start, stop, npoints, seed=0):
-        if min > max:
+        self.start = start
-            raise ValueError("Scan minimum must be less than maximum")
+        self.stop = stop
-        self.min = min
-        self.max = max
         self.npoints = npoints
-        self.sequence = list(LinearScan(min, max, npoints))
+        self.sequence = list(LinearScan(start, stop, npoints))
         shuffle(self.sequence, Random(seed).random)
 
     @portable
@@ -104,7 +105,8 @@ class RandomScan(ScanObject):
 
     def describe(self):
         return {"ty": "RandomScan",
-                "min": self.min, "max": self.max, "npoints": self.npoints}
+                "start": self.start, "stop": self.stop,
+                "npoints": self.npoints}
 
 
 class ExplicitScan(ScanObject):
@@ -142,8 +144,8 @@ class Scannable:
     :param global_step: The step with which the value should be modified by
         up/down buttons in a user interface. The default is the scale divided
         by 10.
-    :param unit: A string representing the unit of the scanned variable, for user
+    :param unit: A string representing the unit of the scanned variable, for
-        interface (UI) purposes.
+        user interface (UI) purposes.
     :param scale: The scale of value for UI purposes. The displayed value is
         divided by the scale.
     :param ndecimals: The number of decimals a UI should use.