wasp-os/wasp/apps/heart.py

# SPDX-License-Identifier: LGPL-3.0-or-later
# Copyright (C) 2020 Daniel Thompson

"""Heart rate monitor
~~~~~~~~~~~~~~~~~~~~~

A graphing heart rate monitor using a PPG sensor.

.. figure:: res/HeartApp.png
    :width: 179
"""

import wasp
import machine
import ppg

class HeartApp():
    """Heart rate monitor application."""
    NAME = 'Heart'

    def foreground(self):
        """Activate the application."""
        wasp.watch.hrs.enable()

        # There is no delay after the enable because the redraw should
        # take long enough it is not needed
        draw = wasp.watch.drawable
        draw.fill()
        draw.set_color(wasp.system.theme('bright'))
        draw.string('PPG graph', 0, 6, width=240)

        wasp.system.request_tick(1000 // 8)

        self._hrdata = ppg.PPG(wasp.watch.hrs.read_hrs())
        self._x = 0

    def background(self):
        wasp.watch.hrs.disable()
        del self._hrdata

    def _subtick(self, ticks):
        """Notify the application that its periodic tick is due."""
        draw = wasp.watch.drawable

        spl = self._hrdata.preprocess(wasp.watch.hrs.read_hrs())

        if len(self._hrdata.data) >= 240:
            draw.set_color(wasp.system.theme('bright'))
            draw.string('{} bpm'.format(self._hrdata.get_heart_rate()),
                        0, 6, width=240)

        # Graph is orange by default...
        color = wasp.system.theme('spot1')

        # If the maths goes wrong lets show it in the chart!
        if spl > 100 or spl < -100:
            color = 0xffff
        if spl > 104 or spl < -104:
            spl = 0
        spl += 104

        x = self._x
        draw.fill(0, x, 32, 1, 208-spl)
        draw.fill(color, x, 239-spl, 1, spl)
        x += 2
        if x >= 240:
            x = 0
        self._x = x

    def tick(self, ticks):
        """This is an outrageous hack but, at present, the RTC can only
        wake us up every 125ms so we implement sub-ticks using a regular
        timer to ensure we can read the sensor at 24Hz.
        """
        t = machine.Timer(id=1, period=8000000)
        t.start()
        self._subtick(1)
        wasp.system.keep_awake()

        while t.time() < 41666:
            pass
        self._subtick(1)

        while t.time() < 83332:
            pass
        self._subtick(1)

        t.stop()
        del t