Add basic application for playback based on NFC tags

Copy and clean up test.py to main.py. Add app module (currently on
app.py, maybe make it a directory later) for application classes.

Implement app.TimerManager to allow scheduling of delayed events in the
micropython async framework.

Implement app.TagPlaybackManager which handles playing back MP3 files
based on the NFC tag reader. Currently, simply plays all MP3 files in a
folder, for which the folder name matches the tag id, in order. Resume,
random and other features not yet supported.

software/src/main.py

@@ -0,0 +1,83 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2024-2025 Matthias Blankertz <matthias@blankertz.org>
+
+import aiorepl
+import asyncio
+import machine
+import micropython
+import os
+import time
+from machine import Pin
+from math import pi, sin, pow
+
+# Own modules
+from app import TimerManager, TagPlaybackManager
+from audiocore import Audiocore
+from mp3player import MP3Player
+from nfc import Nfc
+from rp2_neopixel import NeoPixel
+from rp2_sd import SDCard
+
+micropython.alloc_emergency_exception_buf(100)
+
+
+async def rainbow(np, period=10):
+    def gamma(value, X=2.2):
+        return min(max(int(brightness * pow(value / 255.0, X) * 255.0 + 0.5), 0), 255)
+
+    brightness = 0.5
+    count = 0.0
+    leds = len(np)
+    while True:
+        for i in range(leds):
+            ofs = (count + i) % leds
+            np[i] = (gamma((sin(ofs / leds * 2 * pi) + 1) * 127),
+                     gamma((sin(ofs / leds * 2 * pi + 2/3*pi) + 1) * 127),
+                     gamma((sin(ofs / leds * 2 * pi + 4/3*pi) + 1) * 127))
+        count += 0.2
+        before = time.ticks_ms()
+        await np.async_write()
+        now = time.ticks_ms()
+        if before + 20 > now:
+            await asyncio.sleep_ms(20 - (now - before))
+
+
+# Machine setup
+
+# Set 8 mA drive strength and fast slew rate
+machine.mem32[0x4001c004 + 6*4] = 0x67
+machine.mem32[0x4001c004 + 7*4] = 0x67
+machine.mem32[0x4001c004 + 8*4] = 0x67
+# high prio for proc 1
+machine.mem32[0x40030000 + 0x00] = 0x10
+
+
+# Setup SD card
+try:
+    sd = SDCard(mosi=Pin(3), miso=Pin(4), sck=Pin(2), ss=Pin(5), baudrate=15000000)
+    os.mount(sd, '/sd')
+except OSError as ex:
+    print(f'Failed to setup SD card: {ex}')
+
+# Setup LEDs
+pin = Pin.board.GP16
+np = NeoPixel(pin, 10, sm=1)
+asyncio.create_task(rainbow(np))
+
+# Setup MP3 player
+audioctx = Audiocore(Pin(8), Pin(6))
+player = MP3Player(audioctx)
+player.set_volume(128)
+asyncio.create_task(player.task())
+
+# Setup app
+timer_manager = TimerManager(True)
+playback_manager = TagPlaybackManager(timer_manager, player)
+
+# Setup NFC
+nfc = Nfc(playback_manager.onTagChange)
+
+# Start
+asyncio.create_task(aiorepl.task({'player': player, 'timer_manager': timer_manager,
+                                  'playback_manager': playback_manager}))
+asyncio.get_event_loop().run_forever()