Fix decoding of single-element payload members

src/packages/harp-device/src/harp/device/schema/_emit.py

@@ -104,14 +104,14 @@ class ConverterContext:
     name: str  # yml field key ("__value__" for a whole-register value)
     interface_type: Optional[str]  # the DSL interfaceType (None = raw/native)
     mask: Optional[int]  # bit mask, when the value is bit-packed
-    length: int  # register elements this value spans, at least one
+    length: Optional[int]  # declared element count; None when the schema declares none
     element: np.dtype  # base element dtype of the register, from PayloadType
     element_size: int  # base element byte size of the register
 
     @property
     def span(self) -> int:
         """Byte span of the value, its element count times the element size."""
-        return self.length * self.element_size
+        return (self.length or 1) * self.element_size
 
     @property
     def member_dtype(self) -> np.dtype:
@@ -124,8 +124,8 @@ def member_dtype(self) -> np.dtype:
 
     @property
     def raw_dtype(self) -> np.dtype:
-        """Native passthrough dtype, a sub-array when the value spans more than one element."""
-        if self.length > 1:
+        """Native passthrough dtype, a sub-array when the schema declares an element count."""
+        if self.length is not None:
             return np.dtype((self.element.type, (self.length,)))
         return self.element
 
@@ -319,7 +319,7 @@ def _resolve_converter(self, ctx: ConverterContext) -> Converter[Any]:
         if ctx.mask is not None:
             return IdentityConverter(ctx.member_dtype)  # bit-field: native slice of the element
         if it is None:
-            if ctx.length > 1:
+            if ctx.length is not None:
                 return ArrayConverter(ctx.element, ctx.length)  # raw passthrough, sub-array
             return IdentityConverter(ctx.element)  # raw passthrough, single element
         # A known primitive that didn't fit is re-interpreted per field (``{Name}Converter``);
@@ -343,7 +343,7 @@ def _extension(self, symbol: str, ctx: ConverterContext) -> Converter[Any]:
     def _default(self, member: PayloadMember, type_name: str, ctx: ConverterContext) -> Any:
         """The typed default value of the field, or ``_NO_DEFAULT`` when it has none."""
         _default_value = member.defaultValue if member.defaultValue is not None else member.minValue
-        if _default_value is None or ctx.length > 1:
+        if _default_value is None or ctx.length is not None:
             return _NO_DEFAULT
         value = float(_default_value.root)
         group_mask = self._find_mask(type_name)
@@ -376,7 +376,7 @@ def _build_field(self, key: str, member: PayloadMember, reg: Register) -> Any:
             name=key,
             interface_type=it,
             mask=member.mask,
-            length=member.length or 1,
+            length=member.length,
             element=elem,
             element_size=elem_size,
         )
@@ -451,7 +451,7 @@ def _new_payload(self, class_name: str, owner: str, reg: Register) -> type:
                 name="__value__",
                 interface_type=it,
                 mask=None,
-                length=reg.length or 1,
+                length=reg.length,
                 element=elem,
                 element_size=elem_size,
             )

tests/assets/device.yml

@@ -127,6 +127,30 @@ registers:
   PulseDO0:
     <<: *pulseDO
     address: 43
+  MultiElementPayload:
+    address: 44
+    type: U16
+    length: 3
+    access: Write
+  SingleElementPayload:
+    address: 45
+    type: U16
+    length: 1
+    access: Write
+  MixedMemberLength:
+    address: 46
+    type: U8
+    length: 4
+    access: Write
+    payloadSpec:
+      Absent:
+        offset: 0
+      Single:
+        offset: 1
+        length: 1
+      Multiple:
+        offset: 2
+        length: 2
   StartPulse:
     address: 100
     type: U16

tests/data/test_dataset.py

@@ -21,7 +21,7 @@ def _records(cls, n, seed):
     dtype = cls.payload_class.payload_dtype
     rng = np.random.default_rng(seed)
     raw = rng.integers(0, 128, size=n * dtype.itemsize, dtype=np.uint8)
-    return raw.view(dtype).copy()
+    return np.frombuffer(raw, dtype=dtype, count=n).copy()
 
 
 @pytest.fixture

tests/device/converters.py

@@ -6,8 +6,8 @@
 from harp.protocol import Converter
 
 
-class DataConverter(Converter[int]):
-    """Maps two raw little-endian signed bytes to and from a Python int.
+class DataConverter(Converter[np.int32]):
+    """Maps two raw little-endian signed bytes to and from a numpy int32.
 
     Models interfaceType: int over a two-byte sub-region of the CustomMemberConverter payload.
     """
@@ -18,8 +18,8 @@ def __init__(self) -> None:
         self._length = 2
         self.dtype = np.dtype((np.uint8, (self._length,)))
 
-    def decode_scalar(self, view: np.generic) -> int:
-        return int.from_bytes(bytes(np.asarray(view).tolist()), "little", signed=True)
+    def decode_scalar(self, view: np.generic) -> np.int32:
+        return np.int32(int.from_bytes(bytes(np.asarray(view).tolist()), "little", signed=True))
 
     def decode_batch(self, view: NDArray[np.generic]) -> Any:
         return np.array(
@@ -30,7 +30,7 @@ def decode_batch(self, view: NDArray[np.generic]) -> Any:
             dtype=object,
         )
 
-    def encode_into(self, view: NDArray[np.generic], value: int) -> None:
+    def encode_into(self, view: NDArray[np.generic], value: np.int32) -> None:
         view[...] = np.frombuffer(
             int(value).to_bytes(self._length, "little", signed=True), dtype=np.uint8
         )

tests/device/expected_device.py

@@ -8,6 +8,7 @@
 from numpy.typing import NDArray
 from harp.protocol import (
     AnonymousPayload,
+    ArrayConverter,
     BitMask,
     BoolConverter,
     Field,
@@ -19,6 +20,7 @@
     RegisterBase,
     RegisterS32,
     RegisterU16,
+    RegisterU16Array,
     RegisterU8,
     StringConverter,
     StructPayload,
@@ -44,6 +46,7 @@
     "CustomMemberConverterPayload",
     "BitmaskSplitterPayload",
     "PortDIOSetPayload",
+    "MixedMemberLengthPayload",
     "StartPulsePayload",
     "StartPulseTrainPayload",
     "EncoderModePayload",
@@ -59,6 +62,9 @@
     "PortDIOSet",
     "PulseDOPort0",
     "PulseDO0",
+    "MultiElementPayload",
+    "SingleElementPayload",
+    "MixedMemberLength",
     "StartPulse",
     "StartPulseTrain",
     "EncoderMode",
@@ -100,9 +106,7 @@ class AnalogDataPayload(StructPayload[np.float32], length=6):
     analog0: np.float32 = Field(IdentityConverter(np.float32))
     analog1: np.float32 = Field(IdentityConverter(np.float32), offset=1)
     analog2: np.float32 = Field(IdentityConverter(np.float32), offset=2)
-    accelerometer: NDArray[np.float32] = Field(
-        IdentityConverter(np.dtype((np.float32, (3,)))), offset=3
-    )
+    accelerometer: NDArray[np.float32] = Field(ArrayConverter(np.float32, 3), offset=3)
 
 
 class ComplexConfigurationPayload(StructPayload[np.uint8], length=17):
@@ -122,9 +126,7 @@ class VersionPayload(StructPayload[np.uint8], length=32):
     firmware_version: HarpVersion = Field(HarpVersionConverter(np.uint8), offset=3)
     hardware_version: HarpVersion = Field(HarpVersionConverter(np.uint8), offset=6)
     core_id: str = Field(StringConverter(3), offset=9)
-    interface_hash: NDArray[np.uint8] = Field(
-        IdentityConverter(np.dtype((np.uint8, (20,)))), offset=12
-    )
+    interface_hash: NDArray[np.uint8] = Field(ArrayConverter(np.uint8, 20), offset=12)
 
 
 class CustomPayloadPayload(AnonymousPayload[np.uint32]):
@@ -159,6 +161,14 @@ class PortDIOSetPayload(AnonymousPayload[np.uint8]):
     __value__: PortDigitalIOS = BitMask(enum=PortDigitalIOS)
 
 
+class MixedMemberLengthPayload(StructPayload[np.uint8], length=4):
+    """Represents the payload of the MixedMemberLength register."""
+
+    absent: np.uint8 = Field(IdentityConverter(np.uint8))
+    single: NDArray[np.uint8] = Field(ArrayConverter(np.uint8, 1), offset=1)
+    multiple: NDArray[np.uint8] = Field(ArrayConverter(np.uint8, 2), offset=2)
+
+
 class StartPulsePayload(StructPayload[np.uint16]):
     """Represents the payload of the StartPulse register."""
 
@@ -247,6 +257,22 @@ class PulseDO0(RegisterU16):
     address: ClassVar[int] = 43
 
 
+class MultiElementPayload(RegisterU16Array):
+    address: ClassVar[int] = 44
+    length: int = 3
+
+
+class SingleElementPayload(RegisterU16Array):
+    address: ClassVar[int] = 45
+    length: int = 1
+
+
+class MixedMemberLength(RegisterBase[MixedMemberLengthPayload]):
+    address: ClassVar[int] = 46
+    payload_type: ClassVar[PayloadType] = PayloadType.U8
+    payload_class = MixedMemberLengthPayload
+
+
 class StartPulse(RegisterBase[StartPulsePayload]):
     """Starts a PWM pulse."""
 
@@ -285,6 +311,9 @@ class EncoderMode(RegisterBase[EncoderModeMask]):
     41: PortDIOSet,
     42: PulseDOPort0,
     43: PulseDO0,
+    44: MultiElementPayload,
+    45: SingleElementPayload,
+    46: MixedMemberLength,
     100: StartPulse,
     101: StartPulseTrain,
     103: EncoderMode,

tests/device/test_emit.py

@@ -574,7 +574,7 @@ def _random_records(dtype, n, seed):
     """
     rng = np.random.default_rng(seed)
     raw = rng.integers(0, 128, size=n * dtype.itemsize, dtype=np.uint8)
-    return raw.view(dtype).copy()
+    return np.frombuffer(raw, dtype=dtype, count=n).copy()
 
 
 @pytest.mark.parametrize("name", sorted(_device_registers()))