RSDK-8592 Make single encoder tick even without motor (viamrobotics#4332

)

components/encoder/single/single_encoder.go

@@ -168,13 +168,13 @@ func (e *Encoder) Reconfigure(
 	if e.workers != nil {
 		e.workers.Stop() // Shut down the old interrupt stream
 	}
-	e.start(ctx, board) // Start up the new interrupt stream
+	e.start(board) // Start up the new interrupt stream
 	return nil
 }
 
 // start starts the Encoder background thread. It should only be called when the encoder's
 // background workers have been stopped (or never started).
-func (e *Encoder) start(ctx context.Context, b board.Board) {
+func (e *Encoder) start(b board.Board) {
 	e.workers = utils.NewBackgroundStoppableWorkers()
 
 	encoderChannel := make(chan board.Tick)
@@ -207,7 +207,9 @@ func (e *Encoder) start(ctx context.Context, b board.Board) {
 					atomic.AddInt64(&e.position, dir)
 				}
 			} else {
-				e.logger.CDebug(ctx, "received tick for encoder that isn't connected to a motor; ignoring")
+				// if no motor is attached to the encoder, increase in positive direction.
+				e.logger.Debug("no motor is attached to the encoder, increasing ticks count in the positive direction only")
+				atomic.AddInt64(&e.position, 1)
 			}
 		}
 	})

components/encoder/single/single_encoder_test.go

@@ -112,8 +112,7 @@ func TestEncoder(t *testing.T) {
 		})
 	})
 
-	// this test ensures that digital interrupts are ignored if AttachDirectionalAwareness
-	// is never called
+	// this test ensures that position goes forward if motor not attached.
 	t.Run("run no direction", func(t *testing.T) {
 		enc, err := NewSingleEncoder(ctx, deps, rawcfg, logging.NewTestLogger(t))
 		test.That(t, err, test.ShouldBeNil)
@@ -128,6 +127,42 @@ func TestEncoder(t *testing.T) {
 		// by the encoder worker
 		time.Sleep(50 * time.Millisecond)
 
+		ticks, _, err := enc.Position(context.Background(), encoder.PositionTypeUnspecified, nil)
+		test.That(t, err, test.ShouldBeNil)
+		test.That(t, ticks, test.ShouldEqual, 1)
+	})
+
+	// Taking off directional awareness makes encoder tick forward.
+	t.Run("run motor then no motor", func(t *testing.T) {
+		enc, err := NewSingleEncoder(ctx, deps, rawcfg, logging.NewTestLogger(t))
+		test.That(t, err, test.ShouldBeNil)
+		enc2 := enc.(*Encoder)
+		defer enc2.Close(context.Background())
+
+		m := &FakeDir{-1} // backward
+		enc2.AttachDirectionalAwareness(m)
+
+		err = ii.Tick(context.Background(), true, uint64(time.Now().UnixNano()))
+		test.That(t, err, test.ShouldBeNil)
+
+		testutils.WaitForAssertion(t, func(tb testing.TB) {
+			tb.Helper()
+			ticks, _, err := enc.Position(context.Background(), encoder.PositionTypeUnspecified, nil)
+			test.That(tb, err, test.ShouldBeNil)
+			test.That(tb, ticks, test.ShouldEqual, -1)
+		})
+
+		// take off directional awareness.
+		enc2.m = nil
+
+		err = ii.Tick(context.Background(), true, uint64(time.Now().UnixNano()))
+		test.That(t, err, test.ShouldBeNil)
+
+		// Give the tick time to propagate to encoder
+		// Warning: theres a race condition if the tick has not been processed
+		// by the encoder worker
+		time.Sleep(50 * time.Millisecond)
+
 		ticks, _, err := enc.Position(context.Background(), encoder.PositionTypeUnspecified, nil)
 		test.That(t, err, test.ShouldBeNil)
 		test.That(t, ticks, test.ShouldEqual, 0)