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 import struct
   9 import fcntl
  10 from time import sleep
  11
  12 DEBUG=0
  13 I2C_FILENAME = "/dev/i2c-2"
  14 logger = logging.getLogger(__name__)
  15
  16 class i2c:
  17         I2C_SLAVE = 0x0703  # Use this slave address
  18         __single = None
  19         __lock = threading.Lock()
  20         __parent_owner = None
  21
  22         def __init__(self, addr):
  23                 with i2c.__lock:
  24                         count = 0
  25                         while(i2c.__single):
  26                                 parent = inspect.stack()[1][3]
  27                                 count += 1
  28                                 sleep(0.001)
  29                         if DEBUG:
  30                                 if count > 10:
  31                                         parent_owner = "%s (%d), %s()" % (self.__parent_owner[1], self.__parent_owner[2], self.__parent_owner[3])
  32                                         logger.warning("Error: (%s) I2C blocked %fs by %s!", parent, count*0.001, parent_owner)
  33                                 i2c.__parent_owner = inspect.stack()[1]
  34                         i2c.__single = True
  35                 self.dev = os.open(I2C_FILENAME, os.O_RDWR)
  36                 if self.dev < 0:
  37                         raise IOError("open")
  38                 fcntl.flock(self.dev, fcntl.LOCK_EX)
  39                 fcntl.ioctl(self.dev, i2c.I2C_SLAVE, addr>>1)
  40
  41         def write(self, s):
  42                 num_write = os.write(self.dev, 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 = os.read(self.dev, num)
  49                 if len(buf) != num:
  50                         self.close()
  51                         raise IOError("read: %d" % (len(buf)))
  52                 return buf
  53
  54         def close(self):
  55                 if self.dev:
  56                         os.close(self.dev)
  57                         self.dev = None
  58                         i2c.__single = None
  59
  60
  61 def i2c_write_reg(addr, reg, buf=""):
  62         dev = i2c(addr)
  63         s = struct.pack(">B", reg) + buf
  64         dev.write(s)
  65         dev.close()
  66
  67
  68 def i2c_read_reg(addr, reg, num=1):
  69         i2c_write_reg(addr, reg)
  70
  71         dev = i2c(addr)
  72         s = dev.read(num)
  73         dev.close()
  74         return s
  75
  76
  77 if __name__ == "__main__":
  78         import sys
  79
  80         dev = i2c(0x50)
  81         s = struct.pack(">Bh", int(sys.argv[1]), int(sys.argv[2]))
  82         dev.write(s)
  83         dev.close()