ir_rx/nec.py

   1 # nec.py Decoder for IR remote control using synchronous code
   2 # Supports NEC protocol.
   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 utime import ticks_us, ticks_diff
   9 from ir_rx import IR_RX
  10
  11 class NEC_ABC(IR_RX):
  12     def __init__(self, pin, extended, callback, *args):
  13         # Block lasts <= 80ms (extended mode) and has 68 edges
  14         super().__init__(pin, 68, 80, callback, *args)
  15         self._extended = extended
  16         self._addr = 0
  17
  18     def decode(self, _):
  19         try:
  20             if self.edge > 68:
  21                 raise RuntimeError(self.OVERRUN)
  22             width = ticks_diff(self._times[1], self._times[0])
  23             if width < 4000:  # 9ms leading mark for all valid data
  24                 raise RuntimeError(self.BADSTART)
  25             width = ticks_diff(self._times[2], self._times[1])
  26             if width > 3000:  # 4.5ms space for normal data
  27                 if self.edge < 68:  # Haven't received the correct number of edges
  28                     raise RuntimeError(self.BADBLOCK)
  29                 # Time spaces only (marks are always 562.5µs)
  30                 # Space is 1.6875ms (1) or 562.5µs (0)
  31                 # Skip last bit which is always 1
  32                 val = 0
  33                 for edge in range(3, 68 - 2, 2):
  34                     val >>= 1
  35                     if ticks_diff(self._times[edge + 1], self._times[edge]) > 1120:
  36                         val |= 0x80000000
  37             elif width > 1700: # 2.5ms space for a repeat code. Should have exactly 4 edges.
  38                 raise RuntimeError(self.REPEAT if self.edge == 4 else self.BADREP)  # Treat REPEAT as error.
  39             else:
  40                 raise RuntimeError(self.BADSTART)
  41             addr = val & 0xff  # 8 bit addr
  42             cmd = (val >> 16) & 0xff
  43             if cmd != (val >> 24) ^ 0xff:
  44                 raise RuntimeError(self.BADDATA)
  45             if addr != ((val >> 8) ^ 0xff) & 0xff:  # 8 bit addr doesn't match check
  46                 if not self._extended:
  47                     raise RuntimeError(self.BADADDR)
  48                 addr |= val & 0xff00  # pass assumed 16 bit address to callback
  49             self._addr = addr
  50         except RuntimeError as e:
  51             cmd = e.args[0]
  52             addr = self._addr if cmd == self.REPEAT else 0  # REPEAT uses last address
  53         # Set up for new data burst and run user callback
  54         self.do_callback(cmd, addr, 0, self.REPEAT)
  55
  56 class NEC_8(NEC_ABC):
  57     def __init__(self, pin, callback, *args):
  58         super().__init__(pin, False, callback, *args)
  59
  60 class NEC_16(NEC_ABC):
  61     def __init__(self, pin, callback, *args):
  62         super().__init__(pin, True, callback, *args)