check chip part & version number

cc1101/__init__.py

@@ -0,0 +1,57 @@
+import enum
+
+import spidev
+
+
+class CC1101:
+
+    # Table 45: SPI Address Space
+    _READ_SINGLE_BYTE = 0x80
+
+    class _Register(enum.IntEnum):
+        SRES = 0x30
+        # 29.3 Status Register Details
+        PARTNUM = 0xF0
+        VERSION = 0xF1
+
+    # 29.3 Status Register Details
+    _SUPPORTED_PARTNUM = 0
+    _SUPPORTED_VERSION = 0x14
+
+    def __init__(self) -> None:
+        self._spi = spidev.SpiDev()
+
+    def _reset(self) -> None:
+        assert self._spi.xfer([self._Register.SRES, 0]) == [0x0F, 0x0F]
+
+    def _read_single_byte(self, register: _Register) -> int:
+        response = self._spi.xfer([self._READ_SINGLE_BYTE | register, 0])
+        assert len(response) == 2, response
+        assert response[0] == 0
+        return response[1]
+
+    def __enter__(self) -> "CC1101":
+        # https://docs.python.org/3/reference/datamodel.html#object.__enter__
+        self._spi.open(0, 0)
+        self._spi.max_speed_hz = 55700  # empirical
+        self._reset()
+        partnum = self._read_single_byte(self._Register.PARTNUM)
+        if partnum != self._SUPPORTED_PARTNUM:
+            raise ValueError(
+                "unexpected chip part number {} (expected: {})".format(
+                    partnum, self._SUPPORTED_PARTNUM
+                )
+            )
+        version = self._read_single_byte(self._Register.VERSION)
+        if version != self._SUPPORTED_VERSION:
+            raise ValueError(
+                "unexpected chip version number {} (expected: {})".format(
+                    version, self._SUPPORTED_VERSION
+                )
+            )
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback) -> bool:
+        # https://docs.python.org/3/reference/datamodel.html#object.__exit__
+        self._spi.close()
+        return False

test.py

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+import cc1101
+
+with cc1101.CC1101() as transceiver:
+    print(transceiver)