Check WHO_AM_I at start

controller/python/controller.py

@@ -10,6 +10,10 @@ class FirmwareVersionMismatch(Exception):
     pass
 
 
+class WhoAmIMismatch(Exception):
+    pass
+
+
 class Controller:
 
     I2C_ADDR = 0x57
@@ -31,6 +35,7 @@ class Controller:
         self.i2c_bus = i2c_bus
         self.i2c = smbus.SMBus(self.i2c_bus)
 
+        self.check_who_am_i()
         self.check_firmware_version()
 
     def _read(self, command, n, unpack_spec) -> tuple:
@@ -47,6 +52,16 @@ class Controller:
         should return the same value as Controller.I2C_ADDR."""
         return self._read(self.WHO_AM_I, 1, "B")[0]
 
+    def check_who_am_i(self):
+        """Check that the device answers to WHO_AM_I is correct."""
+        w = self.who_am_i()
+        if w != self.I2C_ADDR:
+            error = (
+                f"WHO_AM_I returns {w:#04x} "
+                f"instead of the expected {self.I2C_ADDR:#04x}"
+            )
+            raise WhoAmIMismatch(error)
+
     def set_max_percentage(self, percent: float):
         """Set the maximum percentage of power which will be used
         (between 1 and 100) for further speed instructions. This has