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+# dev2 - Multi-purpose development board using USB and Ethernet. {{{
+#
+# Copyright (C) 2010 Nicolas Schodet
+#
+# APBTeam:
+# Web: http://apbteam.org/
+# Email: team AT apbteam DOT org
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+#
+# }}}
+"""TWI interface."""
+
+import binascii
+import struct
+
+class ProtocolError (RuntimeError):
+ pass
+
+class Twi:
+ """Interface to dev2 twi module."""
+
+ def __init__ (self, fd):
+ """Initialise and set file object to use."""
+ self.fd = fd
+
+ def _send_command (self, s):
+ """Send command to dev2, return response."""
+ self.fd.write (s)
+ r = self.fd.readline (eol = '\r')
+ if '!' in r:
+ raise ProtocolError
+ else:
+ return r
+
+ def send (self, address, data):
+ """Send data to specified slave address."""
+ s = ''.join (('s%02x' % address, binascii.hexlify (data), '\r'))
+ r = self._send_command (s)
+ if len (r) != 4 or r[0] != 'S' or r[-1] != '\r':
+ raise ProtocolError
+ try:
+ return int (r[1:-1], 16)
+ except ValueError:
+ raise ProtocolError
+
+ def recv (self, address, size):
+ """Receive data from specified slave address."""
+ s = 'r%02x%02x\r' % (address, size)
+ r = self._send_command (s)
+ if len (r) < 2 or r[0] != 'R' or r[-1] != '\r':
+ raise ProtocolError
+ try:
+ return binascii.unhexlify (r[1:-1])
+ except TypeError:
+ raise ProtocolError
+