Merge pull request #2 from kattni/offset

Add offsets, example, fix acceleration.

adafruit_adxl37x.py

@@ -28,14 +28,33 @@
 
 """
 
+from struct import unpack
 from micropython import const
 import adafruit_adxl34x
 
+try:
+    from typing import Tuple, Optional
+
+    # This is only needed for typing
+    import busio
+except ImportError:
+    pass
+
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ADXL37x.git"
 
 _ADXL375_DEFAULT_ADDRESS = const(0x53)
 
+_ADXL347_MULTIPLIER: float = 0.049  # 49mg per lsb
+_STANDARD_GRAVITY: float = 9.80665  # earth standard gravity
+
+_REG_DATAX0: int = const(0x32)  # X-axis data 0
+_REG_DATAX1: int = const(0x33)  # X-axis data 1
+_REG_DATAY0: int = const(0x34)  # Y-axis data 0
+_REG_DATAY1: int = const(0x35)  # Y-axis data 1
+_REG_DATAZ0: int = const(0x36)  # Z-axis data 0
+_REG_DATAZ1: int = const(0x37)  # Z-axis data 1
+
 
 class DataRate(adafruit_adxl34x.DataRate):  # pylint: disable=too-few-public-methods
     """Stub class for data rate."""
@@ -79,17 +98,26 @@ class ADXL375(adafruit_adxl34x.ADXL345):
 
     """
 
-    def __init__(self, i2c, address=None):
+    def __init__(self, i2c: busio.I2C, address: Optional[int] = None):
         super().__init__(
             i2c, address if address is not None else _ADXL375_DEFAULT_ADDRESS
         )
 
     @property
-    def range(self):
+    def acceleration(self) -> Tuple[int, int, int]:
+        """The x, y, z acceleration values returned in a 3-tuple in :math:`m / s ^ 2`"""
+        x, y, z = unpack("<hhh", self._read_register(_REG_DATAX0, 6))
+        x = x * _ADXL347_MULTIPLIER * _STANDARD_GRAVITY
+        y = y * _ADXL347_MULTIPLIER * _STANDARD_GRAVITY
+        z = z * _ADXL347_MULTIPLIER * _STANDARD_GRAVITY
+        return x, y, z
+
+    @property
+    def range(self) -> int:
         """Range is fixed. Updating the range is not implemented."""
-        return
+        raise NotImplementedError("Range not implemented. ADXL375 is fixed at 200G.")
 
     @range.setter
-    def range(self, val):
+    def range(self, val: int) -> None:
         """Range is fixed. Updating the range is not implemented."""
         raise NotImplementedError("Range not implemented. ADXL375 is fixed at 200G.")

examples/adxl37x_offset_calibration.py

@@ -0,0 +1,31 @@
+# SPDX-FileCopyrightText: 2022 Kattni Rembor for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import time
+import board
+import adafruit_adxl37x
+
+i2c = board.STEMMA_I2C()  # uses board.SCL and board.SDA
+accelerometer = adafruit_adxl37x.ADXL375(i2c)
+
+accelerometer.offset = 0, 0, 0
+
+print("Hold accelerometer flat to set offsets to 0, 0, and -1g...")
+time.sleep(1)
+x = accelerometer.raw_x
+y = accelerometer.raw_y
+z = accelerometer.raw_z
+print("Raw x: ", x)
+print("Raw y: ", y)
+print("Raw z: ", z)
+
+accelerometer.offset = (
+    round(-x / 4),
+    round(-y / 4),
+    round(-(z - 20) / 4),  # Z should be '20' at 1g (49mg per bit)
+)
+print("Calibrated offsets: ", accelerometer.offset)
+
+while True:
+    print("%f %f %f m/s^2" % accelerometer.acceleration)
+    time.sleep(0.2)

examples/adxl37x_simpletest.py

@@ -10,5 +10,5 @@
 accelerometer = adafruit_adxl37x.ADXL375(i2c)
 
 while True:
-    print("%f %f %f" % accelerometer.acceleration)
+    print("%f %f %f m/s^2" % accelerometer.acceleration)
     time.sleep(0.2)