Encoder: minimise ISR code.

peterhinch · peterhinch · commit c4f1f83f9cd8 · 2022-04-17T14:44:30.000+01:00
diff --git a/v3/primitives/encoder.py b/v3/primitives/encoder.py
@@ -29,22 +29,20 @@ def __init__(self, pin_x, pin_y, v=0, vmin=None, vmax=None, div=1,
             yirq = pin_y.irq(trigger=trig, handler=self._y_cb)
         asyncio.create_task(self._run(vmin, vmax, div, callback, args))
 
-    # Hardware IRQ's. Duration 36μs on Pyboard 1.
+    # Hardware IRQ's. Duration 36μs on Pyboard 1 ~50μs on ESP32.
+    # IRQ latency: 2nd edge may have occured by the time ISR runs, in
+    # which case there is no movement.
     def _x_cb(self, pin_x):
-        if (x := pin_x()) == self._x:  # IRQ latency: if 2nd edge has
-            return  # occurred there is no movement.
-        self._x = x
-        fwd = x ^ self._pin_y()
-        self._v += 1 if fwd else -1
-        self._tsf.set()
+        if (x := pin_x()) != self._x:
+            self._x = x
+            self._v += 1 if x ^ self._pin_y() else -1
+            self._tsf.set()
 
     def _y_cb(self, pin_y):
-        if (y := pin_y()) == self._y:
-            return
-        self._y = y
-        fwd = y ^ self._pin_x() ^ 1
-        self._v += 1 if fwd else -1
-        self._tsf.set()
+        if (y := pin_y()) != self._y:
+            self._y = y
+            self._v += 1 if y ^ self._pin_x() ^ 1 else -1
+            self._tsf.set()
 
     async def _run(self, vmin, vmax, div, cb, args):
         pv = self._v  # Prior hardware value
