ir_tx/__init__.py

   1 # __init__.py Nonblocking IR blaster
   2 # Runs on Pyboard D or Pyboard 1.x (not Pyboard Lite) and ESP32
   3
   4 # Released under the MIT License (MIT). See LICENSE.
   5
   6 # Copyright (c) 2020 Peter Hinch
   7 from sys import platform
   8 ESP32 = platform == 'esp32'  # Loboris not supported owing to RMT
   9 if ESP32:
  10     from machine import Pin, PWM
  11     from esp32 import RMT
  12 else:
  13     from pyb import Pin, Timer  # Pyboard does not support machine.PWM
  14
  15 from micropython import const
  16 from array import array
  17 from time import ticks_us, ticks_diff
  18 # import micropython
  19 # micropython.alloc_emergency_exception_buf(100)
  20
  21 # On ESP32 gate hardware design is led_on = rmt and carrier
  22
  23 # Shared by NEC
  24 STOP = const(0)  # End of data
  25
  26 # IR abstract base class. Array holds periods in μs between toggling 36/38KHz
  27 # carrier on or off. Physical transmission occurs in an ISR context controlled
  28 # by timer 2 and timer 5. See TRANSMITTER.md for details of operation.
  29 class IR:
  30     _active_high = True  # Hardware turns IRLED on if pin goes high.
  31     _space = 0  # Duty ratio that causes IRLED to be off
  32     timeit = False  # Print timing info
  33
  34     @classmethod
  35     def active_low(cls):
  36         if ESP32:
  37             raise ValueError('Cannot set active low on ESP32')
  38         cls._active_high = False
  39         cls._space = 100
  40
  41     def __init__(self, pin, cfreq, asize, duty, verbose):
  42         if ESP32:
  43             self._rmt = RMT(0, pin=pin, clock_div=80, carrier_freq=cfreq,
  44                             carrier_duty_percent=duty)  # 1μs resolution
  45         else:  # Pyboard
  46             if not IR._active_high:
  47                 duty = 100 - duty
  48             tim = Timer(2, freq=cfreq)  # Timer 2/pin produces 36/38/40KHz carrier
  49             self._ch = tim.channel(1, Timer.PWM, pin=pin)
  50             self._ch.pulse_width_percent(self._space)  # Turn off IR LED
  51             # Pyboard: 0 <= pulse_width_percent <= 100
  52             self._duty = duty
  53             self._tim = Timer(5)  # Timer 5 controls carrier on/off times
  54         self._tcb = self._cb  # Pre-allocate
  55         self._arr = array('H', 0 for _ in range(asize))  # on/off times (μs)
  56         self._mva = memoryview(self._arr)
  57         # Subclass interface
  58         self.verbose = verbose
  59         self.carrier = False  # Notional carrier state while encoding biphase
  60         self.aptr = 0  # Index into array
  61
  62     def _cb(self, t):  # T5 callback, generate a carrier mark or space
  63         t.deinit()
  64         p = self.aptr
  65         v = self._arr[p]
  66         if v == STOP:
  67             self._ch.pulse_width_percent(self._space)  # Turn off IR LED.
  68             return
  69         self._ch.pulse_width_percent(self._space if p & 1 else self._duty)
  70         self._tim.init(prescaler=84, period=v, callback=self._tcb)
  71         self.aptr += 1
  72
  73     # Public interface
  74     # Before populating array, zero pointer, set notional carrier state (off).
  75     def transmit(self, addr, data, toggle=0, validate=False):  # NEC: toggle is unused
  76         t = ticks_us()
  77         if validate:
  78             if addr > self.valid[0] or addr < 0:
  79                 raise ValueError('Address out of range', addr)
  80             if data > self.valid[1] or data < 0:
  81                 raise ValueError('Data out of range', data)
  82             if toggle > self.valid[2] or toggle < 0:
  83                 raise ValueError('Toggle out of range', toggle)
  84         self.aptr = 0  # Inital conditions for tx: index into array
  85         self.carrier = False
  86         self.tx(addr, data, toggle)  # Subclass populates ._arr
  87         self.trigger()  # Initiate transmission
  88         if self.timeit:
  89             dt = ticks_diff(ticks_us(), t)
  90             print('Time = {}μs'.format(dt))
  91
  92     # Subclass interface
  93     def trigger(self):  # Used by NEC to initiate a repeat frame
  94         if ESP32:
  95             self._rmt.write_pulses(tuple(self._mva[0 : self.aptr]), start = 1)
  96         else:
  97             self.append(STOP)
  98             self.aptr = 0  # Reset pointer
  99             self._cb(self._tim)  # Initiate physical transmission.
 100
 101     def append(self, *times):  # Append one or more time peiods to ._arr
 102         for t in times:
 103             self._arr[self.aptr] = t
 104             self.aptr += 1
 105             self.carrier = not self.carrier  # Keep track of carrier state
 106             self.verbose and print('append', t, 'carrier', self.carrier)
 107
 108     def add(self, t):  # Increase last time value (for biphase)
 109         assert t > 0
 110         self.verbose and print('add', t)
 111         # .carrier unaffected
 112         self._arr[self.aptr - 1] += t
 113
 114
 115 # Given an iterable (e.g. list or tuple) of times, emit it as an IR stream.
 116 class Player(IR):
 117
 118     def __init__(self, pin, freq=38000, verbose=False):  # NEC specifies 38KHz
 119         super().__init__(pin, freq, 68, 33, verbose)  # Measured duty ratio 33%
 120
 121     def play(self, lst):
 122         for x, t in enumerate(lst):
 123             self._arr[x] = t
 124         self.aptr = x + 1
 125         self.trigger()