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 import struct
   9 import fcntl
  10 from ctypes import *
  11 from time import sleep
  12
  13 DEBUG=0
  14 I2C_FILENAME = "/dev/i2c-2"
  15 logger = logging.getLogger(__name__)
  16
  17 class i2c:
  18         libc = CDLL("libc.so.6")
  19         I2C_SLAVE = 0x0703  # Use this slave address
  20         __single = None
  21         __lock = threading.Lock()
  22         __parent_owner = None
  23
  24         def __init__(self, addr):
  25                 with i2c.__lock:
  26                         count = 0
  27                         while(i2c.__single):
  28                                 parent = inspect.stack()[1][3]
  29                                 count += 1
  30                                 sleep(0.001)
  31                         if DEBUG:
  32                                 if count > 10:
  33                                         parent_owner = "%s (%d), %s()" % (self.__parent_owner[1], self.__parent_owner[2], self.__parent_owner[3])
  34                                         logger.warning("Error: (%s) I2C blocked %fs by %s!", parent, count*0.001, parent_owner)
  35                                 i2c.__parent_owner = inspect.stack()[1]
  36                         i2c.__single = True
  37                 self.dev = i2c.libc.open(I2C_FILENAME, os.O_RDWR)
  38                 if self.dev < 0:
  39                         raise IOError("open")
  40                 fcntl.flock(self.dev, fcntl.LOCK_EX)
  41                 err = i2c.libc.ioctl(self.dev, i2c.I2C_SLAVE, addr>>1)
  42                 if err < 0:
  43                         raise IOError("ioctl")
  44
  45         def write(self, s):
  46                 num_write = i2c.libc.write(self.dev, s, len(s))
  47                 if num_write != len(s):
  48                         self.close()
  49                         raise IOError("write: %d" % (num_write))
  50
  51         def read(self, num):
  52                 buf = create_string_buffer(num)
  53                 num_read = i2c.libc.read(self.dev, buf, num)
  54                 if num_read != num:
  55                         self.close()
  56                         raise IOError("read: %d" % (num_read))
  57                 return buf.raw
  58
  59         def close(self):
  60                 if self.dev:
  61                         i2c.libc.close(self.dev)
  62                         self.dev = None
  63                         #i2c.__parent_owner = None
  64                         i2c.__single = None
  65
  66         def __del__(self):
  67                 self.close()
  68
  69
  70 def i2c_write_reg(addr, reg, buf):
  71         dev = i2c(addr)
  72         s = struct.pack(">B", reg) + buf
  73         dev.write(s)
  74         dev.close()
  75
  76
  77 def i2c_read_reg(addr, reg, num=1):
  78         dev = i2c(addr)
  79         s = struct.pack(">B", reg)
  80         dev.write(s)
  81         s = dev.read(num)
  82         dev.close()
  83         return s
  84
  85
  86 if __name__ == "__main__":
  87         import struct
  88         import sys
  89
  90         dev = i2c(0x50)
  91         s = struct.pack(">Bh", int(sys.argv[1]), int(sys.argv[2]))
  92         dev.write(s)
  93         dev.close()