ir_tx/nec.py

   1 # nec.py Encoder for IR remote control using synchronous code
   2 # NEC protocol.
   3
   4 # Author: Peter Hinch
   5 # Copyright Peter Hinch 2020 Released under the MIT license
   6
   7 from micropython import const
   8 from ir_tx import IR, STOP
   9
  10 _TBURST = const(563)
  11 _T_ONE = const(1687)
  12
  13 class NEC(IR):
  14     valid = (0xffff, 0xff, 0)  # Max addr, data, toggle
  15
  16     def __init__(self, pin, freq=38000, verbose=False):  # NEC specifies 38KHz
  17         super().__init__(pin, freq, 68, 33, verbose)  # Measured duty ratio 33%
  18
  19     def _bit(self, b):
  20         self.append(_TBURST, _T_ONE if b else _TBURST)
  21
  22     def tx(self, addr, data, _):  # Ignore toggle
  23         self.append(9000, 4500)
  24         if addr < 256:  # Short address: append complement
  25             addr |= ((addr ^ 0xff) << 8)
  26         for _ in range(16):
  27             self._bit(addr & 1)
  28             addr >>= 1
  29         data |= ((data ^ 0xff) << 8)
  30         for _ in range(16):
  31             self._bit(data & 1)
  32             data >>= 1
  33         self.append(_TBURST)
  34
  35     def repeat(self):
  36         self.aptr = 0
  37         self.append(9000, 2250, _TBURST)
  38         self.trigger()  # Initiate physical transmission.