wasp: apps: Step counter application

Currently there's no fancy algorithms to estimate stride length. Just
pure simple step counting directly from the hardware's "intelligence
engine".

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

1 files changed, 53 insertions, 0 deletions

diff --git a/wasp/drivers/bma421.py b/wasp/drivers/bma421.py
new file mode 100644
index 0000000..aae4b59
--- /dev/null
+++ b/wasp/drivers/bma421.py
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# Copyright (C) 2020 Daniel Thompson
+
+"""Bosch BMA421 accelerometer driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+"""
+
+import bma42x
+import time
+
+class BMA421:
+    """BMA421 driver
+
+    .. automethod:: __init__
+    """
+    def __init__(self, i2c):
+        """Configure the driver.
+
+        :param machine.I2C i2c: I2C bus used to access the sensor.
+        """
+        self._dev = bma42x.BMA42X(i2c)
+
+    def reset(self):
+        """Reset and reinitialize the sensor."""
+        dev = self._dev
+
+        # Init, reset, wait for reset, enable I2C watchdog
+        dev.init()
+        dev.set_command_register(0xb6)
+        time.sleep(0.20)
+        dev.set_reg(bma42x.NV_CONFIG_ADDR, 6);
+
+        # Configure the sensor for basic step counting
+        dev.write_config_file()
+        dev.set_accel_enable(True)
+        dev.set_accel_config(odr=bma42x.OUTPUT_DATA_RATE_100HZ,
+                               range=bma42x.ACCEL_RANGE_2G,
+                               bandwidth=bma42x.ACCEL_NORMAL_AVG4,
+                               perf_mode=bma42x.CIC_AVG_MODE)
+        dev.feature_enable(bma42x.STEP_CNTR, True)
+
+    @property
+    def steps(self):
+        """Report the number of steps counted."""
+        return self._dev.step_counter_output()
+
+    @steps.setter
+    def steps(self, value):
+        if value != 0:
+            raise ValueError()
+        # TODO: There is a more efficient way to reset the step counter
+        #       but I haven't looked it up yet!
+        self.reset()