scripts/i2c.py

   1 #!/usr/bin/env python
   2 # -*- coding: iso-8859-15 -*-
   3
   4 import threading
   5 import inspect
   6 import os
   7 import logging
   8 from ctypes import *
   9 from time import sleep
  10
  11 DEBUG=0
  12 logger = logging.getLogger(__name__)
  13
  14 class i2c:
  15         libc = CDLL("libc.so.6")
  16         I2C_SLAVE = 0x0703  # Use this slave address
  17         __single = None
  18         __lock = threading.Lock()
  19         __parent_owner = None
  20
  21         def __init__(self, addr):
  22                 with i2c.__lock:
  23                         count = 0
  24                         while(i2c.__single):
  25                                 parent = inspect.stack()[1][3]
  26                                 count += 1
  27                                 sleep(0.001)
  28                         if DEBUG:
  29                                 if count > 10:
  30                                         parent_owner = "%s (%d), %s()" % (self.__parent_owner[1], self.__parent_owner[2], self.__parent_owner[3])
  31                                         logger.warning("Error: (%s) I2C blocked %fs by %s!", parent, count*0.001, parent_owner)
  32                                 i2c.__parent_owner = inspect.stack()[1]
  33                         i2c.__single = True
  34                 self.dev = i2c.libc.open("/dev/i2c-2", os.O_RDWR)
  35                 if self.dev < 0:
  36                         raise IOError("open")
  37                 err = i2c.libc.ioctl(self.dev, i2c.I2C_SLAVE, addr>>1)
  38                 if err < 0:
  39                         raise IOError("ioctl")
  40
  41         def write(self, s):
  42                 num_write = i2c.libc.write(self.dev, s, len(s))
  43                 if num_write != len(s):
  44                         self.close()
  45                         raise IOError("write: %d" % (num_write))
  46
  47         def read(self, num):
  48                 buf = create_string_buffer(num)
  49                 num_read = i2c.libc.read(self.dev, buf, num)
  50                 if num_read != num:
  51                         self.close()
  52                         raise IOError("read: %d" % (num_read))
  53                 return buf.raw
  54
  55         def close(self):
  56                 if self.dev:
  57                         i2c.libc.close(self.dev)
  58                         self.dev = None
  59                         #i2c.__parent_owner = None
  60                         i2c.__single = None
  61
  62         def __del__(self):
  63                 self.close()
  64
  65 if __name__ == "__main__":
  66         import struct
  67         import sys
  68
  69         dev = i2c(0x50)
  70         s = struct.pack(">Bh", int(sys.argv[1]), int(sys.argv[2]))
  71         dev.write(s)
  72         dev.close()