Merge pull request #34 from kattni/offset

Add offset and offset calibration example.

Author: tekktrik

adafruit_adxl34x.py

@@ -29,15 +29,14 @@
 * Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
 """
 from struct import unpack
-
 from micropython import const
 from adafruit_bus_device import i2c_device
 
 try:
     from typing import Tuple, Dict
 
     # This is only needed for typing
-    import busio  # pylint: disable=unused-import
+    import busio
 except ImportError:
     pass
 
@@ -110,12 +109,12 @@ class DataRate:  # pylint: disable=too-few-public-methods
     """
 
     RATE_3200_HZ: int = const(0b1111)  # 1600Hz Bandwidth   140mA IDD
-    RATE_1600_HZ: int = const(0b1110)  #  800Hz Bandwidth    90mA IDD
-    RATE_800_HZ: int = const(0b1101)  #  400Hz Bandwidth   140mA IDD
-    RATE_400_HZ: int = const(0b1100)  #  200Hz Bandwidth   140mA IDD
-    RATE_200_HZ: int = const(0b1011)  #  100Hz Bandwidth   140mA IDD
-    RATE_100_HZ: int = const(0b1010)  #   50Hz Bandwidth   140mA IDD
-    RATE_50_HZ: int = const(0b1001)  #   25Hz Bandwidth    90mA IDD
+    RATE_1600_HZ: int = const(0b1110)  # 800Hz Bandwidth    90mA IDD
+    RATE_800_HZ: int = const(0b1101)  # 400Hz Bandwidth   140mA IDD
+    RATE_400_HZ: int = const(0b1100)  # 200Hz Bandwidth   140mA IDD
+    RATE_200_HZ: int = const(0b1011)  # 100Hz Bandwidth   140mA IDD
+    RATE_100_HZ: int = const(0b1010)  # 50Hz Bandwidth   140mA IDD
+    RATE_50_HZ: int = const(0b1001)  # 25Hz Bandwidth    90mA IDD
     RATE_25_HZ: int = const(0b1000)  # 12.5Hz Bandwidth    60mA IDD
     RATE_12_5_HZ: int = const(0b0111)  # 6.25Hz Bandwidth    50mA IDD
     RATE_6_25HZ: int = const(0b0110)  # 3.13Hz Bandwidth    45mA IDD
@@ -195,7 +194,22 @@ def acceleration(self) -> Tuple[int, int, int]:
         x = x * _ADXL345_MG2G_MULTIPLIER * _STANDARD_GRAVITY
         y = y * _ADXL345_MG2G_MULTIPLIER * _STANDARD_GRAVITY
         z = z * _ADXL345_MG2G_MULTIPLIER * _STANDARD_GRAVITY
-        return (x, y, z)
+        return x, y, z
+
+    @property
+    def raw_x(self) -> int:
+        """The raw x value."""
+        return unpack("<h", self._read_register(_REG_DATAX0, 2))[0]
+
+    @property
+    def raw_y(self) -> int:
+        """The raw y value."""
+        return unpack("<h", self._read_register(_REG_DATAY0, 2))[0]
+
+    @property
+    def raw_z(self) -> int:
+        """The raw z value."""
+        return unpack("<h", self._read_register(_REG_DATAZ0, 2))[0]
 
     @property
     def events(self) -> Dict[str, bool]:
@@ -312,7 +326,7 @@ def enable_freefall_detection(self, *, threshold: int = 10, time: int = 25) -> N
         self._enabled_interrupts["freefall"] = True
 
     def disable_freefall_detection(self) -> None:
-        "Disable freefall detection"
+        """Disable freefall detection"""
         active_interrupts = self._read_register_unpacked(_REG_INT_ENABLE)
         active_interrupts &= ~_INT_FREE_FALL
         self._write_register_byte(_REG_INT_ENABLE, active_interrupts)
@@ -379,7 +393,7 @@ def enable_tap_detection(
             )
 
     def disable_tap_detection(self) -> None:
-        "Disable tap detection"
+        """Disable tap detection"""
         active_interrupts = self._read_register_unpacked(_REG_INT_ENABLE)
         active_interrupts &= ~_INT_SINGLE_TAP
         active_interrupts &= ~_INT_DOUBLE_TAP
@@ -417,6 +431,23 @@ def range(self, val: int) -> None:
         # write the updated values
         self._write_register_byte(_REG_DATA_FORMAT, format_register)
 
+    @property
+    def offset(self) -> Tuple[int, int, int]:
+        """
+        The x, y, z offsets as a tuple of raw count values.
+
+        See offset_calibration example for usage.
+        """
+        x_offset, y_offset, z_offset = unpack("<bbb", self._read_register(_REG_OFSX, 3))
+        return x_offset, y_offset, z_offset
+
+    @offset.setter
+    def offset(self, val: Tuple[int, int, int]) -> None:
+        x_offset, y_offset, z_offset = val
+        self._write_register_byte(_REG_OFSX, x_offset)
+        self._write_register_byte(_REG_OFSY, y_offset)
+        self._write_register_byte(_REG_OFSZ, z_offset)
+
     def _read_clear_interrupt_source(self) -> int:
         return self._read_register_unpacked(_REG_INT_SOURCE)
 

examples/adxl34x_offset_calibration.py

@@ -0,0 +1,35 @@
+# SPDX-FileCopyrightText: 2022 Kattni Rembor for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import time
+import board
+import adafruit_adxl34x
+
+i2c = board.STEMMA_I2C()  # uses board.SCL and board.SDA
+
+# For ADXL343
+accelerometer = adafruit_adxl34x.ADXL343(i2c)
+# For ADXL345
+# accelerometer = adafruit_adxl34x.ADXL345(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 / 8),
+    round(-y / 8),
+    round(-(z - 250) / 8),  # Z should be '250' at 1g (4mg per bit)
+)
+print("Calibrated offsets: ", accelerometer.offset)
+
+while True:
+    print("%f %f %f m/s^2" % accelerometer.acceleration)
+    time.sleep(0.2)