75 lines
2.7 KiB
Python
75 lines
2.7 KiB
Python
# SPDX-License-Identifier: LGPL-3.0-or-later
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# Copyright (C) 2020 Daniel Thompson
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"""Bosch BMA421 accelerometer driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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"""
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import bma42x
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import time
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# Sensor orientation definition.
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# The 6 most significant bits define the indexes of the x, y, and z values
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# in the acceleration tuple returned by the sensor, while the 3 least
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# significant bits define their sign (1 = keep original sign, 0 = negate).
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#
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# Z index ─────────────────┐
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# Y index ───────────────┐ │
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# X index ─────────────┐ │ │
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# ├┐├┐├┐
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_DEFAULT_ORIENTATION = const(0b010010101)
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# 1 = keep, 0 = negate │││
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# X sign ───────────────────┘││
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# Y sign ────────────────────┘│
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# Z sign ─────────────────────┘
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class BMA421:
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"""BMA421 driver
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.. automethod:: __init__
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"""
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def __init__(self, i2c, orientation=_DEFAULT_ORIENTATION):
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"""Configure the driver.
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:param machine.I2C i2c: I2C bus used to access the sensor.
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"""
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self._dev = bma42x.BMA42X(i2c)
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self._orientation = orientation
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def reset(self):
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"""Reset and reinitialize the sensor."""
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dev = self._dev
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# Init, reset, wait for reset, enable I2C watchdog
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dev.init()
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dev.set_command_register(0xb6)
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time.sleep(0.05)
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dev.set_reg(bma42x.NV_CONFIG_ADDR, 6);
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# Configure the sensor for basic step counting
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dev.write_config_file()
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dev.set_accel_enable(True)
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dev.set_accel_config(odr=bma42x.OUTPUT_DATA_RATE_100HZ,
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range=bma42x.ACCEL_RANGE_2G,
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bandwidth=bma42x.ACCEL_NORMAL_AVG4,
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perf_mode=bma42x.CIC_AVG_MODE)
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dev.feature_enable(bma42x.STEP_CNTR, True)
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@property
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def steps(self):
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"""Report the number of steps counted."""
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return self._dev.step_counter_output()
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@steps.setter
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def steps(self, value):
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if value != 0:
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raise ValueError()
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self._dev.reset_step_counter()
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def accel_xyz(self):
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"""Return a triple with acceleration values"""
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raw = self._dev.read_accel_xyz()
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x = raw[self._orientation >> 7 & 0b11] * ((self._orientation >> 1 & 0b10) - 1)
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y = raw[self._orientation >> 5 & 0b11] * ((self._orientation & 0b10) - 1)
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z = raw[self._orientation >> 3 & 0b11] * ((self._orientation << 1 & 0b10) - 1)
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return (x, y, z)
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