ir_rx.py

   1 # ir_rx.py Decoder for IR remote control using synchronous code
   2 # Supports RC-5 RC-6 mode 0 and NEC protocols.
   3 # For a remote using NEC see https://www.adafruit.com/products/389
   4
   5 # Author: Peter Hinch
   6 # Copyright Peter Hinch 2020 Released under the MIT license
   7
   8 from sys import platform
   9 from micropython import const
  10 from machine import Timer
  11 from array import array
  12 from utime import ticks_us, ticks_diff
  13
  14 if platform == 'pyboard':
  15     from pyb import Pin, ExtInt
  16 else:
  17     from machine import Pin
  18
  19 ESP32 = platform == 'esp32' or platform == 'esp32_LoBo'
  20
  21 # Save RAM
  22 # from micropython import alloc_emergency_exception_buf
  23 # alloc_emergency_exception_buf(100)
  24
  25 # Result codes (accessible to application)
  26 # Repeat button code
  27 REPEAT = -1
  28 # Error codes
  29 BADSTART = -2
  30 BADBLOCK = -3
  31 BADREP = -4
  32 OVERRUN = -5
  33 BADDATA = -6
  34 BADADDR = -7
  35
  36
  37 # On 1st edge start a block timer. While the timer is running, record the time
  38 # of each edge. When the timer times out decode the data. Duration must exceed
  39 # the worst case block transmission time, but be less than the interval between
  40 # a block start and a repeat code start (~108ms depending on protocol)
  41
  42 class IR_RX():
  43     verbose = False
  44     def __init__(self, pin, nedges, tblock, callback, *args):  # Optional args for callback
  45         self._nedges = nedges
  46         self._tblock = tblock
  47         self.callback = callback
  48         self.args = args
  49
  50         self._times = array('i',  (0 for _ in range(nedges + 1)))  # +1 for overrun
  51         if platform == 'pyboard':
  52             ExtInt(pin, ExtInt.IRQ_RISING_FALLING, Pin.PULL_NONE, self._cb_pin)
  53         elif ESP32:
  54             pin.irq(handler = self._cb_pin, trigger = (Pin.IRQ_FALLING | Pin.IRQ_RISING))
  55         else:
  56             pin.irq(handler = self._cb_pin, trigger = (Pin.IRQ_FALLING | Pin.IRQ_RISING), hard = True)
  57         self.edge = 0
  58         self.tim = Timer(-1)  # Sofware timer
  59         self.cb = self.decode
  60
  61
  62     # Pin interrupt. Save time of each edge for later decode.
  63     def _cb_pin(self, line):
  64         t = ticks_us()
  65         # On overrun ignore pulses until software timer times out
  66         if self.edge <= self._nedges:  # Allow 1 extra pulse to record overrun
  67             if not self.edge:  # First edge received
  68                 self.tim.init(period=self._tblock , mode=Timer.ONE_SHOT, callback=self.cb)
  69             self._times[self.edge] = t
  70             self.edge += 1
  71
  72 class NEC_IR(IR_RX):
  73     def __init__(self, pin, callback, extended=True, *args):
  74         # Block lasts <= 80ms and has 68 edges
  75         tblock = 80 if extended else 73  # Allow for some tx tolerance (?)
  76         super().__init__(pin, 68, tblock, callback, *args)
  77         self._extended = extended
  78         self._addr = 0
  79
  80     def decode(self, _):
  81         try:
  82             if self.edge > 68:
  83                 raise RuntimeError(OVERRUN)
  84             width = ticks_diff(self._times[1], self._times[0])
  85             if width < 4000:  # 9ms leading mark for all valid data
  86                 raise RuntimeError(BADSTART)
  87             width = ticks_diff(self._times[2], self._times[1])
  88             if width > 3000:  # 4.5ms space for normal data
  89                 if self.edge < 68:  # Haven't received the correct number of edges
  90                     raise RuntimeError(BADBLOCK)
  91                 # Time spaces only (marks are always 562.5µs)
  92                 # Space is 1.6875ms (1) or 562.5µs (0)
  93                 # Skip last bit which is always 1
  94                 val = 0
  95                 for edge in range(3, 68 - 2, 2):
  96                     val >>= 1
  97                     if ticks_diff(self._times[edge + 1], self._times[edge]) > 1120:
  98                         val |= 0x80000000
  99             elif width > 1700: # 2.5ms space for a repeat code. Should have exactly 4 edges.
 100                 raise RuntimeError(REPEAT if self.edge == 4 else BADREP)  # Treat REPEAT as error.
 101             else:
 102                 raise RuntimeError(BADSTART)
 103             addr = val & 0xff  # 8 bit addr
 104             cmd = (val >> 16) & 0xff
 105             if cmd != (val >> 24) ^ 0xff:
 106                 raise RuntimeError(BADDATA)
 107             if addr != ((val >> 8) ^ 0xff) & 0xff:  # 8 bit addr doesn't match check
 108                 if not self._extended:
 109                     raise RuntimeError(BADADDR)
 110                 addr |= val & 0xff00  # pass assumed 16 bit address to callback
 111             self._addr = addr
 112         except RuntimeError as e:
 113             cmd = e.args[0]
 114             addr = self._addr if cmd == REPEAT else 0  # REPEAT uses last address
 115         self.edge = 0  # Set up for new data burst and run user callback
 116         self.callback(cmd, addr, 0, *self.args)
 117
 118 class RC5_IR(IR_RX):
 119     def __init__(self, pin, callback, *args):
 120         # Block lasts <= 30ms and has <= 28 edges
 121         super().__init__(pin, 28, 30, callback, *args)
 122
 123     def decode(self, _):
 124         try:
 125             nedges = self.edge  # No. of edges detected
 126             if not 14 <= nedges <= 28:
 127                 raise RuntimeError(OVERRUN if nedges > 28 else BADSTART)
 128             # Regenerate bitstream
 129             bits = 0
 130             bit = 1
 131             for x in range(1, nedges):
 132                 width = ticks_diff(self._times[x], self._times[x - 1])
 133                 if not 500 < width < 2000:
 134                     raise RuntimeError(BADBLOCK)
 135                 for _ in range(1 if width < 1334 else 2):
 136                     bits <<= 1
 137                     bits |= bit
 138                 bit ^= 1
 139             self.verbose and print(bin(bits))  # Matches inverted scope waveform
 140             # Decode Manchester code
 141             x = 30
 142             while not bits >> x:
 143                 x -= 1
 144             m0 = 1 << x  # Mask MS two bits (always 01)
 145             m1 = m0 << 1
 146             v = 0  # 14 bit bitstream
 147             for _ in range(14):
 148                 v <<= 1
 149                 b0 = (bits & m0) > 0
 150                 b1 = (bits & m1) > 0
 151                 if b0 == b1:
 152                     raise RuntimeError(BADBLOCK)
 153                 v |= b0
 154                 m0 >>= 2
 155                 m1 >>= 2
 156             # Split into fields (val, addr, ctrl)
 157             val = (v & 0x3f) | (0x40 if ((v >> 12) & 1) else 0)
 158             addr = (v >> 6) & 0x1f
 159             ctrl = (v >> 11) & 1
 160
 161         except RuntimeError as e:
 162             val, addr, ctrl = e.args[0], 0, 0
 163         self.edge = 0  # Set up for new data burst and run user callback
 164         self.callback(val, addr, ctrl, *self.args)
 165
 166 class RC6_M0(IR_RX):
 167     # Even on Pyboard D the 444μs nominal pulses can be recorded as up to 705μs
 168     # Scope shows 360-520 μs (-84μs +76μs relative to nominal)
 169     # Header nominal 2666, 889, 444, 889, 444, 444, 444, 444 carrier ON at end
 170     hdr = ((1800, 4000), (593, 1333), (222, 750), (593, 1333), (222, 750), (222, 750), (222, 750), (222, 750))
 171     def __init__(self, pin, callback, *args):
 172         # Block lasts 23ms nominal and has <=44 edges
 173         super().__init__(pin, 44, 30, callback, *args)
 174
 175     def decode(self, _):
 176         try:
 177             nedges = self.edge  # No. of edges detected
 178             if not 22 <= nedges <= 44:
 179                 raise RuntimeError(OVERRUN if nedges > 28 else BADSTART)
 180             for x, lims in enumerate(self.hdr):
 181                 width = ticks_diff(self._times[x + 1], self._times[x])
 182                 if not (lims[0] < width < lims[1]):
 183                     self.verbose and print('Bad start', x, width, lims)
 184                     raise RuntimeError(BADSTART)
 185             x += 1
 186             width = ticks_diff(self._times[x + 1], self._times[x])
 187             # 2nd bit of last 0 is 444μs (0) or 1333μs (1)
 188             if not 222 < width < 1555:
 189                 self.verbose and print('Bad block 1 Width', width, 'x', x)
 190                 raise RuntimeError(BADBLOCK)
 191             short = width < 889
 192             v = int(not short)
 193             bit = v
 194             bits = 1  # Bits decoded
 195             x += 1 + int(short)
 196             width = ticks_diff(self._times[x + 1], self._times[x])
 197             if not 222 < width < 1555:
 198                 self.verbose and print('Bad block 2 Width', width, 'x', x)
 199                 raise RuntimeError(BADBLOCK)
 200             short = width < 1111
 201             if not short:
 202                 bit ^= 1
 203             x += 1 + int(short)  # If it's short, we know width of next
 204             v <<= 1
 205             v |= bit  # MSB of result
 206             bits += 1
 207             # Decode bitstream
 208             while bits < 17:
 209                 # -1 convert count to index, -1 because we look ahead
 210                 if x > nedges - 2:
 211                     raise RuntimeError(BADBLOCK)
 212                 # width is 444/889 nominal
 213                 width = ticks_diff(self._times[x + 1], self._times[x])
 214                 if not 222 < width < 1111:
 215                     self.verbose and print('Bad block 3 Width', width, 'x', x)
 216                     raise RuntimeError(BADBLOCK)
 217                 short = width < 666
 218                 if not short:
 219                     bit ^= 1
 220                 v <<= 1
 221                 v |= bit
 222                 bits += 1
 223                 x += 1 + int(short)
 224
 225             if self.verbose:
 226                  ss = '20-bit format {:020b} x={} nedges={} bits={}'
 227                  print(ss.format(v, x, nedges, bits))
 228
 229             val = v & 0xff
 230             addr = (v >> 8) & 0xff
 231             ctrl = (v >> 16) & 1
 232         except RuntimeError as e:
 233             val, addr, ctrl = e.args[0], 0, 0
 234         self.edge = 0  # Set up for new data burst and run user callback
 235         self.callback(val, addr, ctrl, *self.args)