ir_rx/mce.py

   1 # mce.py Decoder for IR remote control using synchronous code
   2 # Supports Microsoft MCE edition remote protocol.
   3
   4 # Author: Peter Hinch
   5 # Copyright Peter Hinch 2020 Released under the MIT license
   6
   7 # WARNING: This is experimental and subject to change.
   8
   9 from utime import ticks_us, ticks_diff
  10 from ir_rx import IR_RX
  11
  12 class MCE(IR_RX):
  13     init_cs = 4  # http://www.hifi-remote.com/johnsfine/DecodeIR.html#OrtekMCE says 3
  14     def __init__(self, pin, callback, *args):
  15         # Block lasts ~19ms and has <= 34 edges
  16         super().__init__(pin, 34, 25, callback, *args)
  17
  18     def decode(self, _):
  19         def check(v):
  20             if self.init_cs == -1:
  21                 return True
  22             csum = v >> 12
  23             cs = self.init_cs
  24             for _ in range(12):
  25                 if v & 1:
  26                     cs += 1
  27                 v >>= 1
  28             return cs == csum
  29
  30         try:
  31             t0 = ticks_diff(self._times[1], self._times[0])  # 2000μs mark
  32             t1 = ticks_diff(self._times[2], self._times[1])  # 1000μs space
  33             if not ((1800 < t0 < 2200) and (800 < t1 < 1200)):
  34                 raise RuntimeError(self.BADSTART)
  35             nedges = self.edge  # No. of edges detected
  36             if not 14 <= nedges <= 34:
  37                 raise RuntimeError(self.OVERRUN if nedges > 28 else self.BADSTART)
  38             # Manchester decode
  39             mask = 1
  40             bit = 1
  41             v = 0
  42             x = 2
  43             for _ in range(16):
  44                 # -1 convert count to index, -1 because we look ahead
  45                 if x > nedges - 2:
  46                     raise RuntimeError(self.BADBLOCK)
  47                 # width is 500/1000 nominal
  48                 width = ticks_diff(self._times[x + 1], self._times[x])
  49                 if not 250 < width < 1350:
  50                     self.verbose and print('Bad block 3 Width', width, 'x', x)
  51                     raise RuntimeError(self.BADBLOCK)
  52                 short = int(width < 750)
  53                 bit ^= short ^ 1
  54                 v |= mask if bit else 0
  55                 mask <<= 1
  56                 x += 1 + short
  57
  58             self.verbose and print(bin(v))
  59             print(bin(v))  # TEST
  60             #if not check(v):
  61                 #raise RuntimeError(self.BADDATA)
  62             val = (v >> 6) & 0x3f
  63             addr = v & 0xf  # Constant for all buttons on my remote
  64             ctrl = (v >> 4) & 3
  65
  66         except RuntimeError as e:
  67             val, addr, ctrl = e.args[0], 0, 0
  68         # Set up for new data burst and run user callback/error function
  69         self.do_callback(val, addr, ctrl)