# 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