def openSerial( port = 0, rate = 19200, tout = 60 ):
"""Open serial port for SNAP RepRap communications"""
global serialPort
try:
serialPort = serial.Serial( port, rate, timeout = tout )
except:
raise _RepRapError("You do not have permissions to use the serial port, try running as root")
def getPacket(ser):
bytes = []
# Read in 5 bytes
while len(bytes) <= 4:
byte = ser.read()
if len(byte) > 0:
# If this is the sync then clear the byte buffer.
if byte == SYNC_BYTE:
bytes = []
bytes.append( ord(byte) )
else:
raise _SNAPError("Serial timeout")
# Read the expected packet length from Header Byte 1
packetLength = _breakHDB1( bytes[HDB1_OFFSET] ) + PAYLOAD_OFFSET + 1
while len(bytes) < packetLength:
byte = ser.read()
if len(byte) > 0:
bytes.append( ord(byte) )
else:
raise _SNAPError("Serial timeout")
# We have enough bytes, create packet object
p = Packet()
p._setBytes(bytes)
p._decode()
p._check()
if printIncoming:
p.printPacket("Incoming")
if p.DAB == localAddress:
return p
else:
raise _RepRapError( "Received packet bound for " + str(p.DAB) )