Video player `mpv' controlled by an exercise bike with integrated hall effect sensor.

fahrradkino.py

#!/usr/bin/env python3
 
# Copyright (C) 2015 Oleander Reis <oleander@oleander.cc>
# 
# This software is provided 'as-is', without any express or implied
# warranty.  In no event will the authors be held liable for any damages
# arising from the use of this software.
# 
# Permission is granted to anyone to use this software for any purpose,
# including commercial applications, and to alter it and redistribute it
# freely, subject to the following restrictions:
# 
# 1. The origin of this software must not be misrepresented; you must not
#    claim that you wrote the original software. If you use this software
#    in a product, an acknowledgment in the product documentation would be
#    appreciated but is not required.
# 2. Altered source versions must be plainly marked as such, and must not be
#    misrepresented as being the original software.
# 3. This notice may not be removed or altered from any source distribution.

import RPi.GPIO as GPIO
import time
import socket
import json

hall_sensor_pin = 18  # connect hall-sensor to physical pin 18 (IO-5 on banana pi)
mpv_socket = '/tmp/mpv.socket'
GPIO.setmode(GPIO.BOARD)
GPIO.setup(hall_sensor_pin, GPIO.IN, GPIO.PUD_DOWN)

class Mpv():
    def __init__(self, mpv_socket):
        self.mpv = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        self.mpv.connect(mpv_socket)

    def _recv_reply(self):
        buf = b''
        while b'\n' not in buf:
            tempbuf = self.mpv.recv(1024)
            if not tempbuf: return None
            buf += tempbuf

        return buf

    def set_property(self, key, value):
        cmd = {
            'command': ['set_property', key, value]
        }
        self.mpv.send((json.dumps(cmd) + '\n').encode())  # see `man --pager='less -p ^JSON\ IPC' mpv'
        reply = self._recv_reply()

        return reply

    def play(self):
        return self.set_property('pause', False)

    def pause(self):
        return self.set_property('pause', True)

    def close(self):
        self.mpv.close()


class Lights():
    def __init__(self):
        # 0 = 11, 1 = 12, 2 = 13, 3 = 15, 4 = 16
        self._pins = [11, 12, 13, 15, 16]
        self._current_light_position = 11
        for pin in self._pins:
            GPIO.setup(pin, GPIO.OUT, GPIO.PUD_DOWN)

    def _determine_light_position(self, cadence_milliseconds):
        if cadence_milliseconds > 3000:
            return 11
        elif cadence_milliseconds > 1200:
            return 12
        elif cadence_milliseconds <= 1200 and cadence_milliseconds > 800:
            return 13
        elif cadence_milliseconds <= 800 and cadence_milliseconds > 600:
            return 15
        elif cadence_milliseconds <= 600:
            return 16

    def set_light_position(self, cadence_milliseconds):
        light_position = self._determine_light_position(cadence_milliseconds)

        if self._current_light_position != light_position:
            for pin in self._pins:
                if pin != light_position:
                    GPIO.output(pin, False)
                else:
                    GPIO.output(pin, True)
            self._current_light_position = light_position


class Cadence():
    def __init__(self):
        self.last_milliseconds = 0
        self.delta_milliseconds = 10000

    def _milliseconds_delta(self):
        current_milliseconds = int(round(time.time() * 1000))
        delta_milliseconds = current_milliseconds - self.last_milliseconds

        return current_milliseconds, delta_milliseconds

    def revolution(self, channel):
        delta = self._milliseconds_delta()

        self.last_milliseconds = delta[0]
        self.delta_milliseconds = delta[1]

    def get_current_milliseconds_delta(self):
        return self._milliseconds_delta()[1]


def set_values(cadence, lights):
    if cadence.get_current_milliseconds_delta() > 1200:  # pause when cadence goes just under 1 Hz
        mpv.set_property('contrast', -100)  # brightness seems to be broken in libvdpau-sunxi
        mpv.set_property('saturation', -100)
        mpv.pause()
        lights.set_light_position(cadence.get_current_milliseconds_delta())
    else:
        mpv.play()
        mpv.set_property('contrast', int(20 - cadence.delta_milliseconds / 20))  # FIXME: works but generates illegal values sometimes; mpv is robust
        mpv.set_property('saturation', int(20 - cadence.delta_milliseconds / 15))  # FIXME: set these values smoothly
        #print(int(20 - delta_milliseconds / 20), int(20 - delta_milliseconds / 15))
        lights.set_light_position(cadence.delta_milliseconds)


while not 'mpv' in globals():  # reconnect when mpv hasn't started yet (FIXME: let systemd do this)
    try:
        mpv = Mpv(mpv_socket)
    except (FileNotFoundError, ConnectionRefusedError):
        time.sleep(1)
        pass
lights = Lights()
cadence = Cadence()
GPIO.add_event_detect(hall_sensor_pin, GPIO.RISING, callback=cadence.revolution)

try:
    while True:
        set_values(cadence, lights)
        time.sleep(0.1)
except KeyboardInterrupt:
    mpv.close()
    GPIO.cleanup()
    pass